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13-01-2011 European Project Semester Department of Export Engineering Copenhagen University College of Engineering Lautrupvang 15, 2750 Ballerup RF communication system for professional swimmers Final Report Group 5 EPS-PRJ-EPS-E10 Student name Student number Alex Hughes 100868 Gatien Manzac 100880 Sergio Ortiz Domenech 101044 Ricardo Lόpez Cabañero 101047 Dohwan Kai Kim 100253 Supervisor(s): Emil Piper EPS Group 5 ”Wireless Communication system for professional swimmers” ii Preface History of the project “Wireless communication system for swimmers” is one of the 27 projects in the European Project Semester 2010. The project has been set by the Danish swimming league Sigma and is to be tackled by a small team of international Students. Our group is working on the third phase of the project. From the last groups report we can see that the first group looked at which components to use in their time on the project and the second group developed these ideas and added some basic coding for the final electronic device. The last group to work on this project submitted their final report in June 2005. No work has been done to update this since that time. We do not have the information of when the first group started the project and we have not received the final prototype they produced in their semester. EPS Group 5 ”Wireless Communication system for professional swimmers” iii Acknowledgements During the project we received help from a number of different people and here we would like to thank them. Firstly Thanks to Emil for the guidance throughout the project and the help introducing us to topics we previously had little or no experience of. Secondly we would like to thank all the people who participated in the tests we run for the vital feedback that allowed us to critically analyse the final designs. We would also like to thank all tutors who taught at the start of the semester as all members benefited by learning a lot of new skills and processes during this time. Lastly thank you to all members of our EPS group who have worked hard and contributed to the final outcome of this project. Alex Hughes Gatien Manzac Sergio Ortiz Domenech Ricardo Lόpez Cabañero Dohwan Kai Kim Thursday 2 nd December 2010 EPS Group 5 ”Wireless Communication system for professional swimmers” iv Contents 1. List of Figures ..................................................................................................................... 1 2. Introduction ......................................................................................................................... 3 3. Project work ........................................................................................................................ 4 3.1. Project Specification ................................................................................................... 4 3.2. Team structure ............................................................................................................ 6 3.3. Distribution of Tasks .................................................................................................. 7 3.4. Gantt chart ................................................................................................................... 7 4. The system .......................................................................................................................... 9 4.1. The microphone ........................................................................................................ 11 4.2. Microphone Amplifier .............................................................................................. 12 4.3. CODEC (TLV320AIC1106PW) ............................................................................... 12 4.3.1. What is CODEC? ................................................................................................ 12 4.3.2. General idea of Pulse-Code Modulation (PCM) ................................................. 12 4.3.3. Master Clock and External Clock divider for PCMSYNC ................................. 13 4.3.4. Features of TLV320AIC1106 ............................................................................. 14 4.3.5. Limitations .......................................................................................................... 15 4.3.6. Developing Strategies ......................................................................................... 16 4.3.7. Requirements and Specifications ........................................................................ 17 4.4. The transceiver .......................................................................................................... 19 4.4.1. Frequency ............................................................................................................ 20 4.4.2. Modulation .......................................................................................................... 21 4.4.3. Packet management ............................................................................................ 23 4.4.3.1. Preamble ...................................................................................................... 24 4.4.3.2. Synchronization word .................................................................................. 24 4.4.3.3. Payload management ................................................................................... 24 4.4.3.4. Addressing ................................................................................................... 25 4.4.3.5. CRC (Cyclic Redundancy Check) ............................................................... 25 4.4.3.6. Postamble .................................................................................................... 26 4.5. Interface .................................................................................................................... 26 4.6. Antenna ..................................................................................................................... 26 4.7. Bone speaker ............................................................................................................. 26 4.8. Testing ...................................................................................................................... 26 EPS Group 5 ”Wireless Communication system for professional swimmers” v 4.8.1. CODEC ............................................................................................................... 26 4.8.2. Microphone polarization ..................................................................................... 28 4.8.3. Transceiver .......................................................................................................... 30 4.8.3.1. Using the “Evaluation software” ................................................................. 31 4.8.3.1.1. Connecting two Evaluation Platforms to one Computer ........................ 31 4.8.3.1.2. Setting a board in “receiving” mode ...................................................... 32 4.8.3.1.3. Setting the other board in “transmitting” mode ..................................... 33 4.8.3.2. Testing settings ............................................................................................ 34 4.8.3.3. Testing results .............................................................................................. 34 5. Software ............................................................................................................................ 36 5.1. Codec ........................................................................................................................ 36 5.2. Transceiver ................................................................................................................ 38 6. Other Components ............................................................................................................ 41 6.1. Antenna ..................................................................................................................... 41 6.2. Power supply ............................................................................................................. 44 6.3. Power supply charging .............................................................................................. 44 6.4. Power consumption ................................................................................................... 46 6.5. Water resistance ........................................................................................................ 49 7. Product Form .................................................................................................................... 51 7.1. Development ............................................................................................................. 51 7.1.1. Receiver .............................................................................................................. 51 7.1.1.1. Stage 1 development .................................................................................... 51 7.1.1.2. Stage 2 development .................................................................................... 53 7.1.1.3. Stage 3 development .................................................................................... 55 7.1.1.4. Stage 4 development .................................................................................... 57 7.1.1.5. Stage 5 development .................................................................................... 62 7.1.2. Transmitter Unit .................................................................................................... 65 7.1.2.1. Stage 1 Development ................................................................................... 65 7.1.2.2. Stage 2 Development ................................................................................... 67 7.2. Final Product ............................................................................................................. 68 7.3. Ergonomics ............................................................................................................... 76 7.4. Water Resistance ....................................................................................................... 78 7.5. Materials ................................................................................................................... 78 7.6. Manufacturing ........................................................................................................... 79 7.7. Methods of Use ......................................................................................................... 81 7.8. Durability .................................................................................................................. 81 EPS Group 5 ”Wireless Communication system for professional swimmers” vi 7.9. Location .................................................................................................................... 82 7.10. Testing ...................................................................................................................... 83 7.11 Render ........................................................................................................................... 85 8. Cost ................................................................................................................................... 86 9. Suggestions for following groups ..................................................................................... 91 9.1. Wireless charging ..................................................................................................... 91 9.2. Develop shell ............................................................................................................ 91 9.3. Test Electronics ......................................................................................................... 91 9.4. Induction Charging ................................................................................................... 92 10. Conclusion .................................................................................................................... 92 11. List of References ......................................................................................................... 93 12. Appendix ....................................................................................................................... 96 12.1. Task Distribution ...................................................................................................... 96 12.2. Gantt Chart ................................................................................................................ 98 12.3. Location of Swimmer Device ................................................................................... 99 12.4. Bone speaker ........................................................................................................... 100 12.5. The ear – Anatomy and function ............................................................................ 101 12.6. Questions to Sigma ................................................................................................. 104 12.7. Swimmer device – Another final version ............................................................... 105 12.8. Danish law about frequency in use ......................................................................... 113 12.9. Previous group, Induction Charging ....................................................................... 113 12.10. Supporting Drawings .......................................................................................... 117 EPS Group 5 ”Wireless Communication system for professional swimmers” 1 1. List of Figures Figure 1 : Coach device ............................................................................................................... 9 Figure 2 : Swimmer device .......................................................................................................... 9 Figure 3 : Microphone amplifier ............................................................................................... 12 Figure 4 : Sampling and quantization of a signal (red) for 4-bit PCM....................................... 12 Figure 5 : Clock divider circuit ................................................................................................... 13 Figure 6 : PSPSICE diagram and connection diagram of Dual 4-bit binary counter ................. 14 Figure 7 : Functional block diagram of CODEC (TLV320AIC1106) (ref. CODEC (TLV320AIC1106) datasheet .................................................................................................................................. 14 Figure 8 : Extension circuit for CODEC (TX)............................................................................... 16 Figure 9 : Extension circuit for CODEC (RX) .............................................................................. 16 Figure 10 : Specified block diagram of CODEC(Tx/Rx) .............................................................. 18 Figure 11 : . ADF7022/3 evaluation kit motherboard (1) and ADF7023 evaluation kit (2) attached .................................................................................................................................... 20 Figure 12 : Comparison between transmit spectrum of GFSK modulation (top) and FSK modulation (bottom) ................................................................................................................ 22 Figure 13 : Detail of the result after the gaussian filter............................................................ 23 Figure 14 : Structure of a packet .............................................................................................. 24 Figure 15 : CRC-CCITT polynomial ............................................................................................. 25 Figure 16 : Circuit diagram to build a Clock divider .................................................................. 27 Figure 17 : Results for Clock divider (divided frequency from 2.048 MHz to 8.00 kHz) .......... 28 Figure 18 : Application note of Microphone polarization ........................................................ 29 Figure 19 : Simulation results of microphone polarization ...................................................... 30 Figure 20 : Current state indicator (right bottom of any tab) .................................................. 31 Figure 21 : Position of the switch S4 in the mother board ....................................................... 32 Figure 22 : Connecting two motherboards in one computer ................................................... 32 Figure 23 : Selecting SPORT mode for “receiving” transceiver ................................................ 33 Figure 24 : Transmission Test Mode to “Transmit Carrier” ...................................................... 33 Figure 25 : Testing. Block diagram ............................................................................................ 34 Figure 26 : Sending fake data results. Fake data (above). Output data (below) ...................... 35 Figure 27 : Overview of the testing .......................................................................................... 36 Figure 28 : Schemtaic of the Texas Instruments TLV 320AIC1106 ........................................... 37 Figure 29 : Schematic of the 256 times divider ........................................................................ 37 Figure 30 : Extension circuits of receiving CODEC .................................................................... 38 Figure 31 : extension circuits of receiving CODEC .................................................................... 38 Figure 32 : Screen capture of the “Commands” tab ................................................................. 39 Figure 33 : Screen capture of the “Radio frequency settings” tab ........................................... 40 Figure 34 : Screen capture of the “Transmission/Reception packet settings” tab .................. 40 EPS Group 5 ”Wireless Communication system for professional swimmers” 2 Figure 35 : Screen capture of the “Register view” tab ............................................................. 41 Figure 37 : Sinusoidal signal ...................................................................................................... 42 Figure 36 : Whip antenna ......................................................................................................... 42 Figure 38 : Chip antenna ........................................................................................................... 43 Figure 39 : Chip antenna's dimensions ..................................................................................... 43 Figure 40 : Elongated device CAD model .................................................................................. 57 Figure 41 : External Speaker Device CAD model ...................................................................... 58 Figure 42 : Headset CAD model ................................................................................................ 58 Figure 43 : Diamond CAD model ............................................................................................... 59 Figure 44 : Elongated model photograph ................................................................................. 60 Figure 45 : External speaker photograph ................................................................................. 60 Figure 46 : Headset photograph ............................................................................................... 61 Figure 47 : Diamond model photograph .................................................................................. 61 Figure 48 : exploded view of the final product ......................................................................... 76 Figure 49 : Final CAD head models ........................................................................................... 83 Figure 50 : Unit production table ............................................................................................. 88 Figure 51 : Explode view of the elongated model ..................................................................105 Figure 52 : Repartition in the elongated model .....................................................................106 Figure 53 : Location of the elongated device .........................................................................106 Figure 54 : Main piece of the elongated device .....................................................................107 Figure 55 : Detail of the waterproofing channel ....................................................................107 Figure 57 : Join part of the elongated model .........................................................................108 Figure 56 : Goggle fastening ...................................................................................................108 Figure 58 : Views of the elongated model back piece ............................................................109 Figure 59 : Elongated model assembly process ......................................................................111 Figure 60 : Elongated model sealing .......................................................................................112 Figure 61 : Supporting drawings .............................................................................................127 EPS Group 5 ”Wireless Communication system for professional swimmers” 3 2. Introduction Our team has been brought together through the European project semester (EPS) run through IHK and prior to this no members of the team had ever met before. The EPS programme is designed to bring student together from all over the world to participate in one of a wide range of different available projects. These projects ranged from the very practical designing of a hydraulic pole hammer to the theoretical designing of a marketing strategy for a new dairy product. All members selected 3 of 27 available projects that they would be interested in and then the university distributed the students into international groups of between 3 and 5. Because of this all the other on the project felt that they had skills that would contribute to the final project. 5 students with different skills were assigned to this project for the duration of the semester. The EPS programme is designed to help build skills working in a project team with people from different countries. For this programme English is the common language used and this is supported with English lessons which also form part of the final grade. This is the final report for project group 5 working on the project titled “wireless communication system for professional swimmers”. In this report we look at the final group summary of what has been accomplished over the last semester working at IHK and we will compare that to our initial ideas of what we hoped to achieve. So as not to bog down this report with large amounts of supporting research, we will include in depth discussions of all our research in the appendix and then refer to it through the following sections. EPS Group 5 ”Wireless Communication system for professional swimmers” 10 EPS Group 5 ”Wireless Communication system for professional swimmers” 11 Coach device As you can see in the figures, both devices of the system are made mainly of two complex electronic parts: a CODEC and a transceiver. In the coach device the first part it’s the microphone, which works as an input for the signal to the communication system. Next it’s found the CODEC, that it’s the part that discards any frequency not suitable to be voice and amplifies and converts the analog signal captured by the microphone to digital samples. Now the signal it’s ready to next steps. After the CODEC, the transceiver (set as a transmitter) prepares the voice samples into packets and sends them through the antenna to the swimmers device. Swimmer device The swimmer device is very similar in what about concerns electronic parts. First the antenna and the transceiver (set as a receiver), that debuilds the packets and outputs the data previously sent by the coach’s transceiver. Next the CODEC converts the digital voice samples to an analog signal and prepares it for the next step. Finally, the bone vibration system is the part trough the swimmer is able to hear the coach voice. 4.1. The microphone The microphone is the transducer that converts the sound pressure waves made by the voice of the coach electrical signal (voltage difference). After some research, we found an electret microphone with noise cancelling that fits into our technical specifications (specially operating voltage). It’s the Kwnoles Acoustics MD9752NSZ-1. For testing purposes was used a microphone built in a computer headset. EPS Group 5 ”Wireless Communication system for professional swimmers” 12 4.2. Microphone Amplifier According to the datasheet of CODEC, we are capable to get a microphone gain with 23.5 dB by building an external circuit for microphone. Capacitor values of C1 = 0.22uF and resistor values of R1 = 2 kΩ, R2 = 34 kΩ, and R3 = 510 kΩ are applied. See Section 4.8.2 to obtain more information about the application note of the microphone with gain of 23.5 dB. 4.3. CODEC (TLV320AIC1106PW) 4.3.1. What is CODEC? CODEC is a device or computer program capable of encoding and/or decoding a digital data stream or signal. The word CODEC is a portmanteau of 'compressor-decompressor' or, more commonly, 'coder-decoder'. In this project, CODEC is used in coding analog signals into Pulse-code modulation (PCM) and decoded them back. It is designed to meet Consultive Committee on International Telegraphy and Telephony (CCITT) G.714 requirement. 4.3.2. General idea of Pulse-Code Modulation (PCM) PCM stands for Pulse-code modulation that is a method used to modulate analogue signals to digital signals. As shown in figure 4, we can encode analogue signals as binary numbers, since the number of quantized values is 16 (2 4 ), we call it 4-bit PCM. Figure 3 : Microphone amplifier Figure 4 : Sampling and quantization of a signal (red) for 4-bit PCM EPS Group 5 ”Wireless Communication system for professional swimmers” 13 The 8-bit PCM is also produced in same way but different numbers of quantized values, 256 (2 8 ) in this time. (ref. http://en.wikipedia.org/wiki/Pulse-code_modulation) 4.3.3. Master Clock and External Clock divider for PCMSYNC According to the data sheet, the group needs to supply pulse (2.048 MHz) for master clock and also need to use Divided by 256 clock divider to generate 8 kHz pulse for PCMSYNC, which is derived from the master clock. Master clock will be delivered from a function generator (Agilent 33220A) of a school laboratory, and the clock divider will be made of Dual 4-bit binary counter (DM74LS393N). Dual 4-bit binary counter consists of 8 toggle flip-flop modules. Frequency is divided by 2 when it passes through a toggle flip-flop, therefore a frequency is divided by 256 (2 8 ) when it passes 8 toggle flip-flops. Figure 6 shows PSPICE diagram of it. See Section 4.8.1 to get more information about simulation results. Figure 5 : Clock divider circuit EPS Group 5 ”Wireless Communication system for professional swimmers” 14 4.3.4. Features of TLV320AIC1106 This CODEC (TLV320AIC1106) is designed to perform the encoding analogue-to-digital (A/D) conversion, receive decoding digital-to-analogue (D/A) conversion, and filter transmit and receive signals for voice-band communications systems. Figure 6 : PSPSICE diagram and connection diagram of Dual 4-bit binary counter Figure 7 : Functional block diagram of CODEC (TLV320AIC1106) (ref. CODEC (TLV320AIC1106) datasheet EPS Group 5 ”Wireless Communication system for professional swimmers” 15 In figure 7 shown in above, there is a functional block diagram of CODEC that will be used. It consists of several modules in a chip. These modules are necessary to construct the final device, unless a CODEC is used, each module will have to be built separately. Specific features of TLV320AIC1106 - 20 I/O pins - Operation voltage range : 2.7 V to 3.3 V - Microphone amplifier - Transmit / Receive filter - Analogue / Digital modulator - Input : analog or PCM - Output : PCM or analogue See Section 4.8.1 to obtain more information about simulation results of CODEC. 4.3.5. Limitations Since the delivered CODEC modules are SMD type and also too small to connect other components in a standard-dot PCB board, an extension circuit is needed. The group hoped to build a PCB board with Cadence layout software using, however it was impossible to build it since there was not related parts in its library and even in Texas Instruments web pages. There was no choice but building a circuit board by hand or by other drawing software. EPS Group 5 ”Wireless Communication system for professional swimmers” 16 4.3.6. Developing Strategies Since all related circuits of CODEC were made of analogue components, it is important to be careful about noises might come from junctions, routing, and common ground problems. First of all, in the case of building extension circuits (cf. figure 8, figure 9) for CODEC, since there was not related Cadence layout library, we used Adobe illustrator CS4 instead. Prototype boards were developed by etching kits in IHK. The flowing steps represent how we have built extension boards for CODEC. • Design a circuit diagram with PSPICE • Draw extension lines for CODEC with Illustrator CS4 • Produce extension board at the school etching laboratory • Install decoupling capacitors (100 nF) to prevent unexpected peak from the external power supply – pin 6, 14, 15, and V+ mic • Install a pull-up resistor (10 kΩ) in parallel to Reset button to deliver clear Schmidt trigger to pin 2 It is important to keep in mind that the circuit might produce some high frequency noises because of edges of its wires. To give clear pulse signals to a prototype circuit of CODEC easily, a function generator, Agilent 33220A is recommended to use. In practical product, it will be altered to quarts and a clock divider. Figure 8 : Extension circuit for CODEC (TX) Figure 9 : Extension circuit for CODEC (RX) EPS Group 5 ”Wireless Communication system for professional swimmers” 17 Specification of a function generator (Agilent 33220A): • Mode : Square • Frequency : 2.048 MHz • Amplitude : 3.5 V • Lo level : 0 V • Duty cycle : 50 % Dual 4-bit binary counter is used as Clock divider. See chapter 3.3.3 to obtain more information about Clock divider. Developing Clock divider methods (using a dual 4-bit binary counter – DM74LS393) are by following • Routing circuit as simple and short as possible to minimize interferences of the high frequency • Install decoupling capacitors (100 nF) in parallel to VCC+, and to pin 1 to prevent unexpected peaks from the external power supply and a function generator • Connect pin 6 to 13 • Set clear at Low (0V) allow toggle for T flip-flops 4.3.7. Requirements and Specifications The following system requirements are required to build a prototype circuit of CODEC. • Requirements o Main Components: 5 * CODEC (TLV320AIC1106PW), 2 * Dual 4-bit binary counter (DM74LS393N) o Hardware: 1* Function generator (Agilent 33220A) 1* Oscillator (Agilent DSO7014A) 1 * Power supply 1* Component box 1 * Soldering kit 1 * Etching kits (Light box, Etching tank, Developer) o Software: Cadence SPB 16.2 (PSPICE) EPS Group 5 ”Wireless Communication system for professional swimmers” 18 Adobe Design premium CS4 (Illustrator, Photoshop) • System Specifications o Frequency: 2.048 MHz (MCLK) / 8 kHz (PCMSYNC) o Voltage: +2.0 V (V MIC ) / +3.0 V (DVDD/EARVDD) / +5.0 V (VCC+ @ Clock divider) o Impedance: 16 Ω (earphone) Figure 10 : Specified block diagram of CODEC(Tx/Rx) EPS Group 5 ”Wireless Communication system for professional swimmers” 19 4.4. The transceiver The transceiver is the part responsible to make the wireless communication between the coach and each swimmer device successful. A transceiver is device that can work as a transmitter or as a receiver (or both). Usually transceivers have shared circuitry for both functions in the same integrated circuit or housing. After several weeks to set the final technical specifications of the project by our supervisor and the lag that it implies in the research and development of the project, it was decided that the most suitable transceiver (combined with the groups wishes of using a CODEC instead of a standalone DSP) was the Analog Devices’ ADF7023. The same transceiver is going to be implemented in the coach and the swimmers’ devices. The Analog Devices’ ADF7023 is a very low power, high sensitivity, multi modulation transceiver designed for operation in the European license-free ISM frequency band at 868 MHz. It is suitable for circuit applications that operate under the European ETSI EN300-220. Data rates from 1 kbps to 300 kbps are supported. It also includes a built in 8-bit RISC communications processor, that performs the radio control and the useful and powerful packet management feature (that avoids the using of a separate microprocessor or DSP). EPS Group 5 ”Wireless Communication system for professional swimmers” 26 4.4.3.6. Postamble The communications processor automatically appends two bytes of postamble to the end of the transmitted packet. On the receiver, if the received packet is valid, the RSSI (Received Signal Strength Indicator) is automatically measured during the first postamble byte, and the result is stored in the RSSI_READBACK register. 4.5. Interface The interface for the final devices is an essential part of the design as this forms the bridge between the electronic systems and the person using it. A good or poor interface can greatly affect the quality and usability of the final device. The reasons for choosing different set ups for the interface are discussed at length in section 6.2 and 6.1. All reasons for using specific set ups are explained. During this project there was not enough time to develop a working electronic interface for the devices however the format that will be used has been tested and finalised 4.6. Antenna The choice of antenna will be different for both the coach and the swimmer device. This selection is discussed at full length in Section 6.1. 4.7. Bone speaker Similar to the antenna this section is discussed at much more length in Appendix 12.4. 4.8. Testing 4.8.1. CODEC The aim of CODEC testing is to demonstrate weather CODEC modulates analogue signals and delivers PCM signals to PCMO. CODEC testing was started when CODEC chips (TLV320AIC1106PW) were delivered to us and installed in an extension PCB. CODEC testing was processed by following steps; Clock divider, testing microphone amplifying, and Pulsecode modulation (PCM) testing. EPS Group 5 ”Wireless Communication system for professional swimmers” 27 Clock divider Figure 16 : Circuit diagram to build a Clock divider Measuring specification: Input signals : Pulse wave (2.3V/0V) Frequency : 2.048 MHz (period : 488ns) Simulation results: EPS Group 5 ”Wireless Communication system for professional swimmers” 28 Figure 17 : Results for Clock divider (divided frequency from 2.048 MHz to 8.00 kHz) 4.8.2. Microphone polarization EPS Group 5 ”Wireless Communication system for professional swimmers” 29 Figure 18 : Application note of Microphone polarization Measuring specification: Input voltages : 1.5 Vdc Frequency ranges of input source : 20 Hz < f < 2000 Hz Testing results Since there is no output pin of amplifying gain of 23.5 dB in CODEC, there is no way to figure it out. However, a blue line represents an analogue signal from input sources, and the pink line shows a line of CODEC with microphone polarization. EPS Group 5 ”Wireless Communication system for professional swimmers” 30 Figure 19 : Simulation results of microphone polarization 4.8.3. Transceiver The testing of the transceiver began (late October) after the group received the Analog Devices ADF7023 transceiver evaluation kits and the correspondent mother boards for testing how everything should work work for the coach device and the swimmer device. As commented earlier in the software section, the software is very powerful and for some settings overwhelms our knowledge of telecommunications and telematics involved in a transceiver. Later it is explained how it’s correctly set up the “Evaluation software” for testing a communication system made of two transceivers (coach device and swimmer device). EPS Group 5 ”Wireless Communication system for professional swimmers” 31 4.8.3.1. Using the “Evaluation software” First, Ensure the evaluation mother board with the desired daughter card is connected to the PC via USB cable before running the software. 1. Run the ADF7023 software. 2. Once the software is running press Connect USB. 3. Wait until the BUSY signal above the Connect USB button is turned off before pressing any further buttons on the software interface. 4. After this enter state PHY_ON by pressing the command CMD_PHY_ON. Once you follow these steps, the transceiver should be in the state PHY_ON (“awake” and ready for more commands). You can check it at the right bottom of any tab or in the radio states diagram of the “commands tab”. Figure 20 : Current state indicator (right bottom of any tab) After getting ready one transceiver, you can decide if you want to use another transceiver in the same computer or repeat the process for another transceiver in another computer. 4.8.3.1.1. Connecting two Evaluation Platforms to one Computer 1. On one of the motherboards set switch S4 to position B1 (board 1). On the other board set switch S4 to position B2 (board 2). Connect both boards to the PC with USB cables. EPS Group 5 ”Wireless Communication system for professional swimmers” 32 Figure 21 : Position of the switch S4 in the mother board 2. Open two instances of the evaluation software. On one front panel select board 1 and press Connect USB. On the other front panel select board 2 and press Connect USB. Figure 22 : Connecting two motherboards in one computer 4.8.3.1.2. Setting a board in “receiving” mode 1. In “RF Settings Tab” select the SPORT Mode. Press “Update Needed” if highlighted. This writes the settings to BBRAM and then does a CMD_CONFIG_DEV. EPS Group 5 ”Wireless Communication system for professional swimmers” 33 Figure 23 : Selecting SPORT mode for “receiving” transceiver 2. At the bottom buttons, press CMD_PHY_RX. The part now enters PHY_RX. To exit PHY_RX press CMD_PHY_ON. While in PHY_RX with SPORT mode enabled, the received data demodulated by the ADF7023 will appear at the DR SMA connector on the mother board. A clock synchronized with the demodulated data will appear at the CLK SMA connector. 4.8.3.1.3. Setting the other board in “transmitting” mode First of all, ensure the part is in PHY_ON state. 1. Set Tx Test Mode to “Transmit Carrier” Figure 24 : Transmission Test Mode to “Transmit Carrier” 2. Press CMD_PHY_TX to enter transmit mode (continuous carrier transmission). Press CMD_PHY_END_TX to exit transmit mode and return to PHY_ON Now the two transceivers are ready to be tested, one as a receiver and the other one as a transmitter. EPS Group 5 ”Wireless Communication system for professional swimmers” 34 4.8.3.2. Testing settings After several working days getting familiar about how works the transceiver and solving some troubles, the best results and the closest ones of our specifications were obtained with these settings: • RF/modulation: o Channel frequency: 868,0000 MHz o Frequency deviation: 200,0 KHz o Data rate: 300,0 kbps • Transmitter: o Modulation scheme: GFSK • Receiver: o IF bandwidth: 200 KHz o Demodulation scheme: GFSK o Expected max RF freq error: 100,0 KHz Note: The settings that are not appearing above were set as default. 4.8.3.3. Testing results As far as is known, the device will need at least 64 kbps of data rate to transfer the digital voice signal in real time between the transceivers but there was a big problem, the transceivers were needed to be tested but the CODEC part of the device wasn’t ready yet. The solution was using a fake digital data stream. It was made by the function generator, creating a square wave unipolar signal of 64 KHz of frequency. Figure 25 : Testing. Block diagram Function generator Transceiver (transmitter) ADF7023 Transceiver (transmitter) ADF7023 Oscilloscope EPS Group 5 ”Wireless Communication system for professional swimmers” 35 The group found the solution worked, but not at the speed that was needed to make the communication system viable. Actually it works with acceptable error margins until about 40 KHz, being the perfect performance at a low 20 KHz. Probably the problem it’s just a matter or radio settings of the transceiver. Because of the short time available to test them, our lack of deep knowledge and skills about transceivers and the lack of help we found, it wasn’t known very how to fix them and make them work faster. The packet management testing was not a problematic feature. The group tested this early because it worked as planed in the (brief) user guide provided with the motherboards. However, there was time to learn and keep testing before the final presentation. Figure 26 : Sending fake data results. Fake data (above). Output data (below) EPS Group 5 ”Wireless Communication system for professional swimmers” 42 side of the coach device is a suitable solution for the data transmission to the swimmer receiver. It is also good to notice that whip antennas radiate equally in every direction in a horizontal plane. The wavelength is crucial to determine the size of the antenna and is given by the formula: where: c = light speed (299 792 458 m/s) ߥ = frequency of the signal (in our case: 868 Mhz) The size of the antenna is directly linked to mechanical properties of vibration and resonance of the device. The most efficient size is when the movement amplitude at the end of the whip is the most important. As shows the Fig 37, the antenna enters its first state of resonance when its length equals to the quarter of the wavelength. With the relation [1] it is now possible to know the length of the antenna: Figure 37 : Sinusoidal signal Figure 36 : Whip antenna EPS Group 5 ”Wireless Communication system for professional swimmers” 43 After calculation, the antenna needed to be used in the coach device should measure 8.63cm. Swimmer antenna The main specification about the swimmer antenna choice was the space available in the device. The investigations were focused on tiny antennas, such as chip antennas (cf. Fig 38). As a matter of fact, this kind of antenna is mainly used in hand-held devices or Bluetooth devices and they are known to be the smallest antennas available on the market. Figure 38 : Chip antenna For the swimmer device, after looking in several catalogs, the ANT-868-CHP-x was chosen to be eventually implanted in the final product and as it can be checked on the Fig 39, the size of the antenna is reasonably small for the space available in the swimmer device shell. Figure 39 : Chip antenna's dimensions EPS Group 5 ”Wireless Communication system for professional swimmers” 44 6.2. Power supply The different devices need power supply to work without being plugged. To fulfil this specification, different options were considered during the project. The power supply section can be divided in two parts; one for the coach’s device and another for the swimmer device. For both, the battery has to be rechargeable and as small and lightweight as possible. Regarding on the performance and characteristics, two different kind of battery were analysed: the Lithium-Ion and Lithium-Polymer battery. Indeed, those two types of power supply are really effective, relatively cheap and can be found pretty easily on the market. Especially in the swimmer device, the space is quite restrictive and a flexible battery is the best choice. After several discussions, the Li-Poly type was chosen for both devices because of the flexible cell. A Li-poly battery delivers voltage from about 2.7V (discharged) to about 4.23V (fully charged) and has to be protected from overcharge. An overcharged Li-Poly battery would probably cause explosion or fire; this is why the power consumption needs to be precisely calculated and the battery removed as soon as the voltage drops below approximately 3V. 6.3. Power supply charging It is absolutely critical that every precaution is taken when charging your LiPo battery back. Lithium polymer chargers use a different algorithm than any other type of battery charger. For this reason, a lithium polymer charger must be used when charging your LiPo battery EPS Group 5 ”Wireless Communication system for professional swimmers” 45 back. Using a charger that is not specifically designed for LiPo batteries will damage the battery and could result in an explosion or fire. Lithium polymer battery packs do not develop a "memory" as NiCad batteries do and there is no worry about fully discharging LiPo battery packs before charging them. A LiPo battery will be especially hot immediately after use, another important point is to wait until the battery has reached ambient temperature before charging. Current and voltage are the two variables that must be determined when charging LiPo batteries. The voltage should be set to the nominal voltage of the LiPo battery pack and the current should never exceed a 1C charge rate. Even if most LiPo chargers automatically detect the voltage (or cell count) of the LiPo battery pack, it is always a good idea to double check, or confirm that the charger detects correct the voltage pack to avoid any problem with this very sensitive kind of power supply. For the future, the best solution would be to use an inductive power supply charging. Because of the waterproof requirement, it would be easier charge the battery with such a system and let the device sealed with the battery and the electronics inside. Inductive charging uses the electromagnetic field to transfer energy between two objects. A charging station sends energy through inductive coupling to an electrical device, which stores the energy in the batteries. Because there is a small gap between the two coils, inductive charging is one kind of short-distance wireless energy transfer. Induction chargers typically use an induction coil to create an alternating electromagnetic field from within a charging base station, and a second induction coil in the portable device takes power from the electromagnetic field and converts it back into electrical current to charge the battery. The two induction coils in proximity combine to form an electrical transformer. EPS Group 5 ”Wireless Communication system for professional swimmers” 46 6.4. Power consumption Knowing the different components of the products allows defining the device power consumption for the coach device and the swimmer device (cf. Table 1 and 2). With the voltage supply and the device using time it is possible to determinate the current consumption and the capacity, which is necessary for a battery choice. A 1.25 safety factor is applied to the theoretical value to avoid a total discharge of the different batteries during the utilization but also to compensate for the self discharge of the power supply and to adapt the solution depending on the availability of the market. Table 1 : Power consumption of the coach device Load current consumption / mA x hours of supply / h = capacity / mAh Microphone WM – 034BY 4 x 3 = 12 TLV320AIC1106 7 x 3 = 21 ADF7023 32,1 x 3 = 96,3 theoretical battery capacity 129,3 practical battery capacity 161,6 Table 2 : Power consumption of the swimmer device Load current consumption / mA x hours of supply / h = capacity / mAh ADF7023 12,8 x 3 = 38,4 TLV320AIC1106 7 x 3 = 21 Bone speaker 178 x 3 = 534 theoretical battery capacity 593,4 practical battery capacity 741,8 EPS Group 5 ”Wireless Communication system for professional swimmers” 47 Battery and power supply charging choices: Source: http://www.all-battery.com To adapt the voltage delivered by the battery to the one needed by the components, a voltage adapter could be used. Coach device To reach the 161.6 mAh needed, an association of two cells in parallel is necessary: Polymer Li-Ion Lipo Battery 3.7V 80mAh Table 3 : Swimmer battery specifications values Rated Capacity (mAh) 80 Model Number 30133 Nominal Voltage (V) 3.7 Dimensions (mm) 21(length) x 12(width) x5(thickness) Impedance (m-Ohm) <= 50 Cell Weight (g) 2.4 Max. Charge Current 1 C Max. Charge Voltage (V) 4.2 Max. Discharge Current (mA) 80 Cut-off voltage (V) 2.75 Operation Temperature Charge 0~+45 o C Discharge -20~+60 o C Storage Temperature <= 1 month -10~+35 o C >=6 month -5~+30 o C EPS Group 5 ”Wireless Communication system for professional swimmers” 48 Swimmer device To reach the 741.8 mAh needed, an association of two cells in parallel is necessary: Polymer Li-Ion Battery 3.7V 430mAh Table 4 :430mAh coach battery specifications values Electrical 3.7V, 430mAh Max charging rate 430mA (1C) Max Dis-Charging Rate 900mA (2C) Dimensions (mm) 48(length) x 30(width) x 3(thickness) Cell Weight (g) 11 Polymer Li-Ion Battery 3.7V 300mAh Table 5 : 300mAh coach battery specifications values Electrical 3.7V, 300mAh Max charging rate 300mA (1C) Max discharging rate 300mA (1C) Continuous discharge current 60mAh Dimensions (mm) 40(length) x 15(width) x 5.6(thickness) Cell Weight (g) 4 EPS Group 5 ”Wireless Communication system for professional swimmers” 49 Power supply charging choice TLP-2000 Tenergy Universal Smart Charger for Li-Ion/Polymer battery Pack Features and Benefits • Smart universal charger for Li-Ion and Li-Polymer battery pack with capacity > 500mAh • 4 Voltage selections at 3.7v 7.4v 11.1v and 14.8v • Charges pack made of 1 to 4 cells • Universal 100V - 240V AC input for worldwide power usage • 500 mA constant charging current. • Automatic charging stop when battery pack is fully charged , or when each cell 's voltage reaches 4.2V peak • LED indication: Red means " In Charging " and Green means " Full " or "open circuits " • With Tamiya Conncetor • Weight: 4.5 oz • Dimension: 1.5" x 1" x 4" • Price: $20.85 6.5. Water resistance Water resistance is defined as the in DIN8310 as the ability to resist the penetration of water inside the device. DIN 8310 is the standard that watches are tested against to determine the level of water resistance they comply with. This is the appropriate scale to measure the two different devices water resistance against. The change as a product is immersed further EPS Group 5 ”Wireless Communication system for professional swimmers” 50 under the surface of water is pressure and this is the reason that some devices can be waterproof to 10m but no further. Pressure is measured in Bar, 1 Bar can be defined as 1 kg of force being applied across each cm 2 of our bodies. 1 Bar is also the pressure a person standing at sea level will be subjected to under the force of the atmosphere. As the person climbs higher into the atmosphere the pressure decreases however as the person is submerged in water and starts to go deeper the pressure will increase. For the purpose of being in the same units as DIN 8310 it is important to convert working in Bar to atmospheres. The conversion rate is 1 bar = 0.980665 atmospheres or atm. Here is a rough breakdown of what each level of water resistance means. Level of Resistance Classification Application 0 atm not water resistant No water contact 3 atm water resistant Rain 5 atm water resistant 50m Bathing 10 atm water resistant 100m Swimming 20 atm water resistant 200m Free diving As you can see from this table, the receiver device should achieve a rating of 10atm or high to be suitable for its intended environment. Although the team did not have the time or the facilities to test to this standard, it is something that will be essential in the further development of the final product. EPS Group 5 ”Wireless Communication system for professional swimmers” 51 7. Product Form The form is split into two parts, the receiver and the transmitter. The majority of the design work went into the receiver (swimmers device) as the functionality of this part is much more critical to the overall success of the project. First the development of the receiver will be discussed broken down into the 5 stages of the design process that were passed through, secondly the development of the Coach device will be discussed as it passes through 3 stages of design. After this each final product will be discussed at length and the justifications of the main design points will be given. 7.1. Development 7.1.1. Receiver 7.1.1.1. Stage 1 development At the initial stage of the project the group used the basic information gathered in the research phase to familiarise itself with the topic area and give a strong basis to design from. At this stage of the project the designers did not know whether the swimmers would be wearing goggles, swimming hats or nothing which meant that a wide range of ideas were developed to try and address all of these areas. The team at this stage also did not know how large the final electronics solution was likely to be and so casings for both very small circuits as well as very large circuits were developed with the majority of the designs focusing somewhere in the middle. In total the group produced more than 40 individual designs at this stage. Here are some of the most interesting designs that were developed and what the team thought of each one; One of the first ideas generated was aimed as a solution to create a sort of Lycra or neoprene support to hold the device between the swimmers shoulders at the top of their back, The idea behind this design was to create a method of placing a very large unit on the swimmer with as little EPS Group 5 ”Wireless Communication system for professional swimmers” 58 Figure 41 : External Speaker Device CAD model Figure 42 : Headset CAD model EPS Group 5 ”Wireless Communication system for professional swimmers” 59 Figure 43 : Diamond CAD model Each model was produced using the ergonomics research (discussed later) and also fitted to a CAD model head we used for reference during this stage. This was the first time any of the ideas had been converted into a 3D model and so a lot of development had to be done of areas of the devices which had not been considered in the drawn ideas. The main thing that was added to the designs in this stage was the exact dimensions for being compatible with the goggles used and also the swimmers head. Once these models were finished they were all passed onto Emil to be produced as 3D form Prototypes. These Prototypes gave the group a lot of feedback on the designs and brought up a lot of points that had previously not occurred to the group. Here are the physical forms that were produced in this stage. Long Speaker Device EPS Group 5 ”Wireless Communication system for professional swimmers” 60 This device used two external clips to go round the goggle strap and aimed to mount the bone speaker directly beneath the strap for maximum contact with the swimmer. The electronics are housed in the area that hangs below the strap and are all encased inside the shell of the product. This initial device is low profile and looks as if it will add a minimal amount of drag to the swimmers which is important in their training. The clips hold the product very securely although it can be relatively difficult to put the strap into the fixing. The other major problem with this device is that the length of it means that the swimmer cannot easily tilt their head back without the device causing some discomfort. External Speaker Device The ergonomics of this device meant that the first observation was how well it fitted to the back of everyone’s head. This device is significantly bigger than any of the other devices and because it has such a large surface area in contact with the back of the swimmers head it means that it had to be shaped on 2 planes to ensure a comfortable fit. The detail that had to go into achieving this was very high and so these measurements were useful to retain for fine tuning the final model. The second major point was that this product was very large compared to the other models. Because of this it appeared that it would have a very large effect on the swimmer due to its bulkiness. The external mounting of the speaker proved to be a good idea as this gave a good amount of contact for Figure 44 : Elongated model photograph Figure 45 : External speaker photograph EPS Group 5 ”Wireless Communication system for professional swimmers” 61 transmission of the vibration, however it negated the problem of using so much internal space to house the bone speaker. Finally this product used a groove cut into its surface to slot the strap into. Although the fit was not as secure as the previous device, it proved very easy to put the strap into the groove. One disadvantage of this method however was the cut for the strap took away space that could be used inside the product. Headset Although this device used a lot of ergonomics data to create, it was a completely different set to the previous device as the path of the headband follows a very different path. This was by far the hardest model to get the shape right on and unfortunately the calculations for attaching round the ear proved to be inaccurate and so the prototype does not fir as well as hoped for. This device was also criticised as its use of 2 bone speakers would significantly increase the power consumption and would not improve sound quality enough to justify this. This product would be significantly harder to manufacture and the only real advantage is that it will produce the lowest amount of drag from these final ideas and the increased sound quality could be useful for the swimmer. These advantages however do not outweigh the disadvantages and the design does not have the scope at this strange to evolve to minimise these weaknesses. For this reason this design will be left at this stage and will not be developed further. Diamond The final model that was developed to this stage was the diamond, This model used a version of the groove cut method to hold the strap in place although this time a shallower groove was tested out, this meant that less space was taken from the internal space available. This product was quite small and very low profile. Because of this it looked like Figure 47 : Diamond model photograph Figure 46 : Headset photograph EPS Group 5 ”Wireless Communication system for professional swimmers” 62 a good solution to the problem. In development it was assumed that because of the products small contact surface area, the ergonomics component of the design would be smaller. In testing however this product proved to be uncomfortable as it was not curved enough to fit the head easily. The benefits and weaknesses of this design appear to be the opposite to the benefits and weaknesses of the second design, “External mounted speaker” and so the next stage of development will look to combine these two designs into 1 and give a more suitable final outcome. Some dry testing of these model was done using a set of goggles and a swimming cap and it was decided that the in the next stage of design the external speaker and the long speaker device should be developed further. The long speaker design should be altered to allow better movement for the swimmer and the external speaker design should be merged with the diamond device to get the best benefits of both. 7.1.1.5. Stage 5 development In this stage of development the two designs that were selected in the previous stage have been drastically modified to provide products that should match the initial requirements. At this stage the designs are going to each be produced in the form that they would each finish in. This means that where the models were previously produced as solid blocks to test the basic form, this time they must be produced with sufficient space to allow the electronics to fit inside and should also be produced with the final method of manufacture in mind. These designs are also required to conform to the requirements set for waterproofing. Here are the revised CAD models exploded to show the new detail added. External Speaker EPS Group 5 ”Wireless Communication system for professional swimmers” 63 EPS Group 5 ”Wireless Communication system for professional swimmers” 64 Long Speaker Device External Speaker As you can see the model here is radically different to the model it was based on in the previous section. The bulky device has been trimmed down to a slim shape that barely exceeds the maximum height of the bone speaker. The profile has also been stretched slightly upwards to help guide it into the natural curve of the swimmers head and further reduce the drag that will be felt. The groove for the goggle strap was kept the same as in the initial device because although it now takes up an even bigger percentage of available internal room, the benefits of how well the previous design worked outweighed this problem. The internal cavity has just enough space to fit all of the pieces that will be required in the final product and this space has been maximised by hollowing out the door that fits onto the front of the device to seal it. The waterproofing is based around using a rubber ring between the two layers to create a water tight seal. Long Speaker Device As described in the testing section the group then dry tested these two products against each other to ascertain which product would be the most suitable for use with the swimmers. As seen in the previous CAD model this design was developed as extensively as the model we finally selected. The decision to bring two models to a final stage like this was EPS Group 5 ”Wireless Communication system for professional swimmers” 65 to give us the best possible choice when we came to making the final decision. This product could have easily been used for the final device and in the feedback we got from testing there was very little to separate the two products. We dry tested this product with 20 different volunteers using both the swimming cap and the goggles in each test and the results show that the volunteers slightly preferred the external speaker device based on the fact that it stayed in place easier and it was easier to attach to the strap. Because of this the External speaker device has been carried forwards to be used as the final design. 7.1.2. Transmitter Unit Because the transmitter or coach device is much less critical in terms of design it meant that the group spent that majority of its focus on making sure that the Swimmers receiver device was as well developed as it could be. Because of this it meant that the Coach device only went through 2 phases of design. This is not to say however that significant thought did not go into selecting a design that would fit the purpose effectively. 7.1.2.1. Stage 1 Development In the first stage of design the team drew out a large number of ideas that could be implemented into the coach device and made about 10 initial ideas for forms that the device could take. It was agreed that this device should have a good level of waterproofing however it is far less critical than than the waterproofing of the receiver device. During the initial design process a lot of methods of channel selection were discussed with the electronics side of the project and this helped set some limitations for the format of the interface. Here are 2 of the different ideas that were considered for this section. Touch Screen The first idea is a touch screen device that is protected by a rugged rubber outer case. The outer casing comes EPS Group 5 ”Wireless Communication system for professional swimmers” 66 further forwards than the front of the screen and so should protect the unit from any fall resulting in an impact on a flat surface. This design could however be vulnerable to drops on edges or corners. As the floors in pools are usually tiled it means that any fall could easily damage this product. Because of this a touch screen idea may be a liability and the gains of using it are unlikely to be sufficient to justify the extra cost or risk. The device incorporates a built in internal microphone and also a 3.5mm jack socket which allows the coach to add in an external microphone and attach this to a headset. This could be very useful in minimising the disturbance of the equipment on the coaches actual job which should be monitoring the swimmers. Twist Button The second design went away from the touch screen device and instead focused on keeping the equipment much smaller. This would be with the intention that the coach can attach it to their clothes as they move around the pool. In an effort to minimise the size the most space efficient manner of adding a channel selector was to use a twist switch instead of individual buttons. The big drawback of this is that 2 swimmers cannot be selected at the same time and it can often be difficult for the coach to see which swimmer they have selected. This would serve to distract the coach from their main job and thus the design is flawed. Another weak point in this design is that if the transmitter unit is kept significantly smaller than the previous design then there may not be room to house sufficient batteries which would harm the devices usability. By making this product very small it will increase cost and decrease performance for a benefit that is quite low on the list of priorities for this product. For that reason this design will not be continued. Out of all the designs done for this piece of equipment all were very similar to the touch screen one but incorporated various different features which separated them. Some of the features were good ideas and these were saved and noted while some of the ideas were poor and discarded. Because the devices were all very similar it meant that we were able to merge all of the best ideas in to a single design. This was the design we decided to carry forwards into the next stage of development. EPS Group 5 ”Wireless Communication system for professional swimmers” 67 7.1.2.2. Stage 2 Development In this stage a design was decided upon which did not have the same drawbacks as the touch screen device shown before but that would also be very intuitive for the coach to use and would provide minimal distraction. Because the function of this device is quite simple it was decided that the product should also be simple and although the design is well thought through there are very few unnecessary frills added to the design. Here is the design once we had put it through Solidworks 3D modelling software. This design incorporates a number of features aimed at making the device as intuitive as possible for the coach to use. After a group meeting on the design and some refinements to the sealing method used the design was passed onto Emil to be printed in 3D. At the time of submission of the report the group is waiting for the model to be printed due to some small delays. The final specification will be discussed at length in the following section. EPS Group 5 ”Wireless Communication system for professional swimmers” 74 a flat surface it makes the sealing much more efficient and less susceptible to failures caused by tiny errors in manufacturing. To make sure that this doesn’t waste too much space the door has been cut to a thickness of 1.8mm inside the area of the seal. This gives a cavity where the battery will be able to fit into the final device. The two screw holes are bigger than the thread of a 3mm screw so that as the screws bite into the hole on the second piece it will pull this tight and create a better seal for the product. Finally the place for the screw heads has been recessed so that the back of the device will be smooth for the swimmer and will avoid causing any irritation. Main Piece The main shell of this product has been refined down from a much larger device and the group believes that this is the smallest possible size the final device could be made and still retain a good functionality. The shape of this component has been altered since the design stage and is now taller to help the curve of the product merge with the natural curve of the swimmers head. This will help to reduce the effect of drag on the product. In the research stage it was discovered that even something as minor as putting the goggle strap over the swimming hat instead of under it could add 2% drag to the swimmer. The curve of the inside of the device has been reused from the large model as this was well researched and received a lot of positive feedback when used on a much larger device. As this device is smaller, the accuracy of these stats become less important however by using such well researched data it means that the final product will have a very comfortable secure fit on the swimmers head. The method of coming to these measurements is discussed in the following ergonomics section. The channel on this device was an exact copy of the channel initially designed for use on the bigger model, however, after a lot of positive feedback on the ease of using a channel of these dimensions it was decided that it should be kept for this model. As the model is smaller the channel is shorter and also due to the research in the durability section the ends EPS Group 5 ”Wireless Communication system for professional swimmers” 75 of the channel have been slightly reshaped. The picture here highlights in red the alteration that was made to this. The next point of the design is the cavity at the bottom of the main shell into which the bone speaker will fit. In order to ensure a clean smooth surface between the device shell and the bone speaker, a thin wall at the front of the cavity was shaped to fit accurately to the curvature of the bone speaker. In manufacture the bone speaker will be mounted directly to this wall using a brittle adhesive and then when this has set a relatively hard silicone will be used to fill all the gaps around the speaker and produce a water tight seal. The benefit of attaching like this, in addition to guiding the speaker, is that through this brittle join the vibrations from the speaker will be able to propagate into the main shell and help to increase the transmission surface area across the entire device. Above the bone speaker mounting cavity is a channel cut through into the main electronics cavity. This allows the electrical connection to be made with the power supply and additional electronics. Over all this design effectively addresses the requirements of the specification and serves as an innovative solution to the initial problem. The next few sections will review different aspects of the design in more detail. Finally here is an additional exploded view with all the EPS Group 5 ”Wireless Communication system for professional swimmers” 76 components inside the product. This shows how all of the pieces will fit in the final construction. Figure 48 : exploded view of the final product 7.3. Ergonomics This section will look at the detailed ergonomics work that went into producing the final curves used on the product. Because the device that the research was originally intended for was quite large it was important that it was fitted to the users head across 2 different planes. To get suitable measurements for the product a large number of different card curves were cut at different radius. All the X axis forms were made 110mm long as this is the length needed for the final model and likewise the Y axis forms were all cut to 50mm. To get a number of samples each on had a uniform curve cut into it to a different depth. EPS Group 5 ”Wireless Communication system for professional swimmers” 77 The aim of this exercise was not to find the shape which the most people liked but to find a shape that would suit the largest range of people. To do this each curve was tested on our series of 40 volunteers who rated each shape 1 to 4 on comfort 4 being highest. Here is a sample of one of the people that was asked. Y Axis Cut depth (mm) 10 15 20 25 30 35 40 Review 2 2 3 4 2 1 1 X Axis Cut depth (mm) 20 25 30 35 40 45 50 55 60 65 Review 1 2 2 3 3 4 4 3 1 1 As you can see from these results, the person was most comfortable with a Y axis cut of 35mm and an X axis cut of 45-50mm. It also shows that if the decide is curved too tightly it becomes uncomfortable faster than if it is out by the same amount in the other direction. When plotted in a graph we can see a standard distribution curve of the range of peoples preferences. From this we can see that to account for the majority of people the device should be slightly shallower cut than is average. The person shown here is typical across the Y axis however slightly larger on the X axis. The final results showed that we should select a x axis curve of 40mm and a Y axis curve of 25mm. by selecting this the worst rating for each would be a 2 and by eliminating the 10% most extreme results the lowest ranking was a 3. Similarly the Y axis had a lowest ranking of 3 to start with and by eliminating the most extreme 10% the vast majority rated the curve as a 4. To test that this combination of curves was correct a card jig that covered both axis was constructed and tested on the same 40 people all of which said the 2 curves felt comfortable on the back of their head. EPS Group 5 ”Wireless Communication system for professional swimmers” 78 7.4. Water Resistance As described in the previous water resistance section the final receiver product must be capable of withstanding 10atm of pressure to pass the waterproofing requirement. To achieve this, the final receiver device incorporates a rubber seat that passes around the entire join between the door and the main device. This seal is extended to for a full loop around all of the screws and is made in one solid piece to avoid any leaks. When the screws are tightened this seal is squashed between the two layers and the seal is formed. Currently we are unable to test the device to see whether this method of sealing conforms to the specified level however some basic tests at low depths have shown positive results. If the seal should start to fail before it reaches the depths we need it to be functional at then a groove and ridge can be added around the path of the seal to aid with the sealing and should this fail an additional screw could be added at the top of the device however this would take a significant amount of space up which is required for the electronics. The coach device is not required to have the same level of sealing as the receiver and so we chose to finish this to be resistant to about 5atm. For this we have designed the device with a channel and ridge that runs right the way around the join between the two halves of its construction. Like in the previous device a rubber seal will follow this and help seal it from any leaks. The coach device requires a lot of buttons and switches on its surface and so for this reason it would be hard to finish it to the level that is required of the receiver. In addition to this rubber seal the internal electronics will be sealed inside a bag to protect them. This bag is suitable for up to 10atm which is more than enough for the device. 7.5. Materials For the swimmer device the group decided to select ABS as its primary material choice. This is for a number of reasons; firstly because the product is required to be used in chlorinated water it was important to select a polymer that displays a good chemical resistance to chlorine. The second important factor that meant the group favoured this polymer was that ABS displays good scratch and impact resistance. This is extremely important as the final products (as specified in the brief) should be targeted to last around 3 years with failure rates in the first 2 years below 10%. To achieve this target the plastic needs to be durable EPS Group 5 ”Wireless Communication system for professional swimmers” 79 and although ABS is more expensive than some of the other options it is necessary if the group is to meet this target. Finally as discussed in the manufacturing section, the process selected for producing these components will be injection moulding. As a thermo plastic whit good flow properties ABS is compatible with this method of construction. For the coach device the group was stuck between using ABS again or using a cheaper alternative such as HDPE or PC. In the end the decision was made to use ABS again due to the fact that the actual components being used in the product are relatively cheap however the product is expected to be aimed at a relatively high price. Because of this quality was put ahead of saving money and ABS was selected again for its scratch resistance which will help prolong the life of the product. 7.6. Manufacturing As it said in the section before, the two pieces which constitute the case will be made of ABS plastic. Two standard 3mm screws will be used for join both parts. To assure a slight movement in the bonespeaker for a correct location in the back of the head, it will be introduce through the slot in the main part of the device. This part is a little bit wider than the part of the bonespeaker which is introduced in the casing. Silicone will then be used to seal both components. First of all, two moulds will be needed for producing the main parts from thermoplastic using injection moulding. Electronic components will be ordered directly to the company which produces them, with the appropriate changes made in the programming. This will be the same for the screws and the bonespeaker. With all components manufactured, an assembly line will be used to facilitate the manual construction process. Shown below are the two parts which are needed to be built. The rest of the components will be ordered from the appropriate companies. The reason that the cost section displays a 6.500€ set up cost for the injection moulding is because mould manufacture costs are proportional to workshop time needed to produce them. In this case the design is very complex and so will take a long time to manufacture the moulds. EPS Group 5 ”Wireless Communication system for professional swimmers” 80 MAIN CASING: Function: To hold the electronic parts and provide the possibility to hold the device with the goggle´s band. Units: One. Dimensions: 110 x 55 x 35mm Assembly: With two screws to join it with the back cap and using silicone to fix the bonespeaker. Manufacturing: Injection moulding. Material: ABS Requirement: Rigidity, water resistant. Door: Function: Close the device making pressure assuring waterproofing. Units: One. Dimensions: 100 x 35 x 10mm approx Assembly: Two screws to join it with the back cap component. To ensure a permanent hold these will be secured with locktight glue and silicone will be used to seal over the heads. Manufacturing: Injection moulding. EPS Group 5 ”Wireless Communication system for professional swimmers” 81 Material: ABS Requirement: Rigidity, water resistant. 7.7. Methods of Use In the beginning of the project, a wide amount of research was done. In this search, a lot of swimming goggles were seen. Paying attention to the different sizes of the goggle’s band. Considering that this part is made of a malleable material, the slot of the device has a dimension which can be attached to most of the swimming goggles. A common use of the device is detailed next. 1.- Cross the goggle´s band trough the back groove of the device. 2.- Put the goggles assuring that the bone-speaker is making a correct pressure in the back of the head. 3.- Put your swimming cap. 7.8. Durability By using Solidworks fatigue calculation software it is possible to predict what stresses will be put on the product over its lifetime and ensure that the construction and material choice is sufficient to withstand the 3 year lifespan defined in the initial specification. Here is a graphical representation of how well our product will fare over its lifetime. EPS Group 5 ”Wireless Communication system for professional swimmers” 82 For this the material was selected as ABS and the forces considered were general wear and tear around the edges as well as the goggle strap being put in and out of the band strap a total of 3,285 times. This is assuming the product is used 3 times a day and 365 days a year. The conclusion from Solidworks was that the edges of the channel would break within the first year. This is shown by the green areas in the picture above, the blue areas will not break under normal usage. This has been rectified by reshaping the channel slightly to reduce the catch of the band on the ends of it. The revised model will stand up to the stresses for a minimum of 5 years. This is however is assuming no big drops or times getting trodden on and so the actual product lifespan is likely to be closer to the specified 3 years. 7.9. Location As discussed in the Appendix section 12.3 there are a number of different sites that conduct the sound from the bone speaker better than others. The final receiver device is designed to effectively combine with the zones located on the back of the head to transmit a clear signal to the inner ear. As you can see in the appendix the zone selected by us is not the best at EPS Group 5 ”Wireless Communication system for professional swimmers” 83 conducting the vibrations however due to the ease of access it was selected over the more conductive zone behind the ears. We did a significant amount of experimentation around this site and found that the transmission at this point would be easily sufficient for our product to work. A large benefit of selecting this zone is that the goggle strap passes close to it and allows us a point to anchor the device to. Figure 49 : Final CAD head models 7.10. Testing The testing that has been referred to through this section has often be referred to as dry testing. This is because although the final receiver unit is intended to be used in the pool, the most time effective way to test the device during stage 4 development was to get a sample group of people to wear it as if they were about to go swimming with it and to give us their immediate reactions. Because of the level of detail that was actually required at this stage going to the pool and trying to get a large enough group of people to collect significant data from would have been a poor investment of time. A test on the final complete device would have been good to go to the pool for however due to time constraints the group was unable to do this before the end of the project. To try to lessen the impact of this on the group it was decided a second dry test would be done on the final device to get some final EPS Group 5 ”Wireless Communication system for professional swimmers” 90 Note: * indicates estimated EPS Group 5 ”Wireless Communication system for professional swimmers” 91 9. Suggestions for following groups 9.1. Wireless charging Due to a lack of time, the group was not able to look into developing the induction charging device however the previous group did some basic research into this subject: This is a subject area that would be valuable for the next group to research further into. Because of this it is important that the information collected by the first group is not wasted and passed onto the next group. The last groups work on this subject is included in Appendix 12.10. We take no responsibility for this work. 9.2. Develop shell Although the shell for the receiver has been developed to a point where the members all feel that it would be ready to go into production, the transmitter unit could still be developed further to give a better overall project. Things that could be developed are combining the buttons with a working interface system for the electronics side, working on methods of making the device more portable for the coach, and also research into whether the space at the top of the device, currently occupied with a small note pad, could be used more efficiently. Currently the product struggles to get below the £600 per full set price limit our group set. The next stage in the products development should be to reduce this number to £4,500 and work to bring down more costs through better design. 9.3. Test Electronics As main problem we had that the evaluation kit for the CODEC that we finally found more suitable for our design and requirements seemed to be not in stock in any retailer or distributor. We would be grateful if our supervisor had advised us earlier of this fact to have time to search for another solution. EPS Group 5 ”Wireless Communication system for professional swimmers” 92 That implied that we only got free samples of the CODEC itself, and they were SMD components so weld them over an PCB was extremely difficult due to the tiny dimensions of the CODEC. Although we actually succeeded in designing and making our own PCB board for testing the CODEC in a short time, it was proved as a fountain of problems due to high frequency requirements and it didn’t work well. Summarising, we suggest to following groups that select this project to follow the path of making the devices with a CODEC and a transceiver but finding another CODEC with similar characteristics ensuring that it’s correspondent evaluation kit is available. 9.4. Induction Charging This semester the group has been heavily focused on progressing the main body of the project as far as is possible within the time and because of this the group has not looked into Induction charging in anywhere near the depth that would be needed to start making progress in this area. In Appendix 12.9 we have included the last groups initial work into this area and from this we hope that the next team to tackle this project will be able to develop this further. 10. Conclusion The EPS programme has helped all members become much more comfortable working in an international team and being responsible for running their own project. Through this project the team has had a lot of different deadlines to work on top of managing a challenging project where different setbacks have to be overcome to reach the final goal. Although the project did not reach the stage of having the final circuits built, the team feels that they have done very well given delays in acquiring the electronics and the amount of additional work that had to be done throughout the project time. Because this project had such a big split between the electrical side and the casing side it has at times been a challenge not to separate these two sides too much. One way the group has overcome this is by not sticking rigidly to the side of the project we were assigned but EPS Group 5 ”Wireless Communication system for professional swimmers” 93 instead switching between the two sides and learning about areas members were previously weak in. Another big benefit that all members have experienced is the project management structuring that was taught at the start of the year. Out of the whole group Kai was the only one who had been formally taught these strategies of management before and so the team members gained a lot from this and were all able to see how they could be applied to the project. The overall feeling from all the group members was that we were lucky to be assigned team mates that all worked well together and had similar expectations for the semester to one another. This has helped the members to get the most out of the project and has really added to the experience. 11. List of References Books GREEN, J.H. , 2005, “The Irwin Handbook of Telecommunications”. 5th edition (McGraw-Hill) STALLINGS, W. , 1999, “Data and Computer Communications”. 6th edition (Prentice Hall) TANNENBAUM, A.S. , 2003, “Computer networks”. 4th edition (Pearson) Articles • Ritter, T. , 1986, “The Great CRC Mystery”, Dr. Dobb's Journal of Software Tools. http://www.ciphersbyritter.com/ARTS/CRCMYST.HTM Legislation • “Notification on Danish air-interface no. 00 032 for low-power radio equipment with integrated or dedicated antenna intended for telemetry, remote-control purposes, EPS Group 5 ”Wireless Communication system for professional swimmers” 94 alarms, speech and data transfer in certain frequency bands between 6 MHz and 246 GHz” http://en.itst.dk/spectrum-equipment/r-tte-equipment/filarkiv/radio-interface- regulations/032%20INTERFACE-SRD-ENG.pdf • “EXTRACT Of Amateur Radio related provisions in Denmark relevant to radio amateurs using amateur radio stations during short stays in Denmark in accordance with CEPT recommendations T/R 61-01 or (05)06” http://www.edr.dk • The Radio Regulations, Edition of 2008 http://www.itu.int/publ/R-REG-RR-2008/en • International Telecommunication Union ITU-R FAQ http://www.itu.int/ITU-R/terrestrial/faq/index.html Datasheets • Analog Devices ADF7023 (transceiver) http://www.analog.com/static/imported-files/data_sheets/ADF7023.pdf • Texas Instruments TLV320AIC1106 (PCM CODEC) http://www.ti.com/lit/gpn/tlv320aic1106 • Knowles Acoustics MD9752NSZ-1 (noise cancelling microphone) http://www.farnell.com/datasheets/302370.pdf • L-com HG903RD-SM (antenna) http://69.84.140.50/multimedia/datasheets/DS_HG903RD-SM.PDF • Antenna Factor ANT-868-CHP-x (chip antenna) http://www.antennafactor.com/resources/data-guides/ant-xxx-chp-x.pdf • Huaying International HY-00001 (bone speaker) http://huayingint.en.made-in-china.com/product/TeOnqLpMYGUb/China-Bone- Conduction-Transducer.html Others EPS Group 5 ”Wireless Communication system for professional swimmers” 95 Wikipedia, http://www.wikipedia.org EPS Group 5 ”Wireless Communication system for professional swimmers” 96 12. Appendix 12.1. Task Distribution OBS WBS Alex Hughes Gatien Manzac Kai Kim Sergio Ortiz Domenech Ricardo López Cabañero Comments Find suitable transceiver S R Find suitable microprocessor /DSP S R Create accurate programming codes R S Research location of the device S R Develop product form R S S Work to optimize bone vibration technology S R Produce a working electronics prototype S S R Produce a form prototype R S S EPS Group 5 ”Wireless Communication system for professional swimmers” 97 Find suitable materials R S S Ensure that the final form prototype is waterproof S R Investigate effects of chlorine on the final product S R S Research and implementation of a suitable battery R S S (If there is time) Develop the inductive charging system S S S S S Review the earlier complete system S R S We don’t know yet if we need to build again some electronic parts EPS Group 5 ”Wireless Communication system for professional swimmers” 98 12.2. Gantt Chart EPS Group 5 ”Wireless Communication system for professional swimmers” 99 12.3. Location of Swimmer Device One of the most important parts in the casing is where to place the receiver unit. Mainly, we need to focus on three aspects: hydrodynamics, bone conduction and comfort. About the hydrodynamic, we have researched several swimming´s videos. We have noticed that, because of the form of the head, the less disturbing head´s zone for the training would be localized on the back´s surface between the ears. According to some studios, we found one with a chart which indicates different parts of the head with measurements of the sound´s level. Results of the study indicate that the condyle (an articular prominence of a bone) is the most receptive location for a BC transducer because it generates the lowest overall threshold levels. The “best” effective location appears to be the condyle, followed by the mastoid and vertex. Although the jawbone ranked third, it was very difficult to hold the vibrator in place at this location. Next images show it more understandable: EPS Group 5 ”Wireless Communication system for professional swimmers” 106 Different zones to hold the parts. Bone-speaker´s zone Electric´s zo General dimensions of the device compared with the head. Figure 53 : Location of the elongated device Figure 52 : Repartition in the elongated model EPS Group 5 ”Wireless Communication system for professional swimmers” 107 Characteristics of the parts. Main piece This piece is the most important part of the device (cf. Fig. 43). The top of the form, narrower, this will hold the bone-speaker. The bottom part will be used to house the rest of the components. In the lateral (cf. Fig. 44), there is a slot to put the join part which will be fixed thanks to three 3mm stainless screws. Material: Polycarbonate. Manufacturing: Injection molding. Dimensions: 80 x 25 x 23 mm. Figure 54 : Main piece of the elongated device Figure 55 : Detail of the waterproofing channel EPS Group 5 ”Wireless Communication system for professional swimmers” 108 As said before, there are different goggle´s band sizes. To overcome that, two small steps had been designed to do easier the use with most of the bands (cf Fig. 45). Join part Figure 57 : Join part of the elongated model Waterproofing has been the most difficult goal to overcome. This model is thought to use that piece between the two main parts and make pressure in the back piece (cf. Fig 46). Material: Some kind of elastomer such as thermoplastic polyurethane (TPU) or silicone. Figure 56 : Goggle fastening EPS Group 5 ”Wireless Communication system for professional swimmers” 109 Manufacturing: Injection molding. Dimensions: 78 x 23 x 1 mm. Back piece This piece is used to seal the back of the device. It has been calibrated to the ergonomics research done for the project. It has a thickness of 1 mm, except for lateral, which has a thickness of 3 mm due to the waterproofing. The place for the screw heads has been recessed so that the back of the device will be smooth for the swimmer and will avoid causing any irritation. For a better sound´s transmitting, there is a little cavity in the top part which houses the bone-speaker. Material: Polycarbonate. Manufacturing: Injection molding. Dimensions: 78 x 23 x 1 mm. Apart from this, three standard M1.6 x 5 mm stainless steel screws will be needed to do the force between the two pieces and the electronic parts. Figure 58 : Views of the elongated model back piece EPS Group 5 ”Wireless Communication system for professional swimmers” 110 Assembly EPS Group 5 ”Wireless Communication system for professional swimmers” 111 Figure 59 : Elongated model assembly process EPS Group 5 ”Wireless Communication system for professional swimmers” 112 Final sealing Although the design of this model is finished, the information about it it’s not as detailed as the chosen one, because the efforts of the team were focused on the main model. Figure 60 : Elongated model sealing EPS Group 5 ”Wireless Communication system for professional swimmers” 113 12.8. Danish law about frequency in use The frequency chosen for the carrier signal of the transceivers needs to be within legal limits of the Danish law. After a very tough researching on the “National IT and Telecom Agency” (which is department under the Danish Ministry of Science Technology and Innovation) and the ”Experimenterende Danske Radioamatører og Radioamatørernes Forlag ApS” websites were found two important documents that helps us on complaining the radio electric requirements and certify that our system can be used legally in Denmark. As a summary, that the frequency bands 868.000 – 868.600 MHz, 868.700 – 869.200 MHz and 869.700 – 870.000 MHz can be used legally in Denmark without demanding any type of license. Note: Documents “Notification on Danish air-interface no. 00 032 for low-power radio equipment with integrated or dedicated antenna intended for telemetry, remote-control purposes, alarms, speech and data transfer in certain frequency bands between 6 MHz and 246 GHz” and “EXTRACT Of Amateur Radio related provisions in Denmark relevant to radio amateurs using amateur radio stations during short stays in Denmark in accordance with CEPT recommendations T/R 61-01 or (05)06” can be found in the annex. 12.9. Previous group, Induction Charging Here is the work done by the previous group on the subject on induction charging. It is important to note that we take no responsibility for this work however it is important to include this for the following group. Inductive wireless charging Introduction Solid-state charging can improve the handling of many electric devices. In particular affected are devices being used several times during the day and being recharged continually, like cell EPS Group 5 ”Wireless Communication system for professional swimmers” 114 phones, electric toothbrushes, electric shavers etc. Beside it, there are other applications where the security of the operator is important. One example is electric cars, which have to be recharged in all weathers; another example is devices in explosive area, where sparks are not allowed. Another field of application results in devices, where no plug connectors are possible. In this group belongs on the one hand medical implants (pace maker, biotelemetry) and on the other hand absolute encapsulated, hermetic devices, e.g. for underwater application. Wireless charging Wireless charging is a method, where the energy for charging a battery is transferred without a plug connector (wireless) and without an electric contact (solid-state). The energy could be provided with following methods: forms of energy force component modifier output range efficiency factor optical radiation LED solar cell mW m < 1% mechanical motion piezo modifier W um 80% capacitive voltage electrode uW um 60% inductive current coil kW cm 98% electromagnetic field wave antenna uW km < 1% In practice the inductive transmission with two coils goes into action (transformers coupling). Figure 11.9: Block diagram of an inductive charger (11) adapter primary side secondary side mobile part mains electr ic user EPS Group 5 ”Wireless Communication system for professional swimmers” 115 The contrast to a conventional transformer is only, that the primary and the secondary side are mechanical separated. For charging the mobile part is placed in the adapter. The electric power is transmitted between the two parts in an inductive way, i.e. without a direct electric contact. The distance is only about a few millimetres. After charge the primary side of the transformer remains stationary in the adapter. The secondary side is in the mobile part and is abstracted out of the adapter during using. Advantages: • No contact debit / wearing • Potential-free • Hermetic closed • Error free Disadvantages: • Adapter and mobile part form a constructive unit Examples for inductive wireless charging: application power benefit electrical toothbrush mW easy handling implants mW no plug possible medical devices W easy handling electric cars kW handling, safety hearing aids mW handling resp. implant explosion protective device W solid-state, hermetic While conventional charger consists of two functional blocks, charger and power control, the inductive wireless charging makes allowance for a third component, the wireless transfer way (power and control signal). EPS Group 5 ”Wireless Communication system for professional swimmers” 122 EPS Group 5 ”Wireless Communication system for professional swimmers” 123 EPS Group 5 ”Wireless Communication system for professional swimmers” 124 Appendix 18 EPS Group 5 ”Wireless Communication system for professional swimmers” 125 EPS Group 5 ”Wireless Communication system for professional swimmers” 126 EPS Group 5 ”Wireless Communication system for professional swimmers” 127 Figure 61 : Supporting drawings