Biomechanics Gait Analysis Lab - Biomedical Engineering ...

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3. Technical Description The Biomechanics Gait Analysis Laboratory equipment consists of Force Sensitive Resistor Insoles, Footswitch Insoles, insole driver circuits, Telemetry devices, and National Instruments BNC-2120 and PXI-6040E in the PXI-1031 box. The Force Sensitive Resistor Insoles and Footswitch Insoles are powered through the drive circuit, which is part of the transmitter telemetry device. The transmitter device sends the signal to the receiver telemetry device, which is connected to the BNC-2120. The BNC-2120 receives analog or digital signals and relays the signals to the PXI-6040E, which provides the data to the LabVIEW® software program in a computer. Since the system begins with input from the insoles, a detailed description of the insoles will be given first, followed by the remaining equipment in order as listed above. Force Sensitive Resistor (FSR) Insoles The FSR insoles are comprised of force sensitive resistors, sandwiched between cut-to-size shoe insoles and taped together with Gorilla brand duct tape. A diagram of an FSR insole is shown in Figure 35. Rubber disks are placed on either side of the sensing area to concentrate the force directly onto the sensing area to provide a better reading, which is indicated in Figure 36. The FSR has a three male square pin connector, also shown in Figure 36 and Figure 35. The middle connector is connected to ground and the two outer pins are used for the voltage supply input and the voltage output. The two outer pins can be either used as the input or the output. The force sensor is an extremely thin, flexible printed circuit. The force sensor is made of two layers of a polyester/polyimide substrate sheet. For each layer, conductive silver is applied, on top of which a layer of pressure-sensitive ink is applied. An adhesive joins the two layers of substrate together to complete the force sensor. The active sensing area is outlined by the silver circle around the pressure-sensitive ink, which can be seen in Figure 36. The silver lines extend from the sensing area to the two outer connector male square pins to form the leads. Page 42
The sensors act as a force sensing resistors in an electrical circuit, so that when it’s unloaded, the resistance is quite high, and when it’s loaded, the resistance is rather low. The resistance will vary as the sensor is loaded and unloaded. Using a digital multimeter, the resistance or force can be read by connecting the probes to the outer two pins, and then apply a force to the sensing area. The digital multimeter must be turned on and the dial set to the resistance or voltage reading option. The FSRs can range up to 1000 lbs by reducing the resistor value and/or voltage of a driver circuit, which is used in this design, shown in Figure 35, and will be described next. Left Insole Design Bottom Layer Top Layer Rubber Disks FSR Cut-to-size shoe Insole Duct Tape Lead Wires FSR Figure 35: FSR Insole design Page 43
Page 1 and 2: Biomechanics Gait Analysis Lab Oper
Page 3 and 4: PARTS AND ACCESSORIES The following
Page 5 and 6: Table of Contents Section Page Numb
Page 7 and 8: The new laboratory utilizes a numbe
Page 9 and 10: Figure 4: FSR Insole The FSR’s ar
Page 11 and 12: Figure 8: Transmitter Box Figure 9:
Page 13 and 14: The receiver connects directly to t
Page 15 and 16: Figure 15:Footswitch Insoles LabVIE
Page 17 and 18: Figure 17: Men’s FSR Insoles LabV
Page 19 and 20: Figure 19:Womens FSR Insoles LabVIE
Page 21 and 22: 3. Place the fanny pack around the
Page 23 and 24: Figure 25: Footswitch Output Wire C
Page 25 and 26: 14. Press the OFF button on the blo
Page 27 and 28: Figure 30: Corrected Toe Sensor Dat
Page 29 and 30: 2. Place the transmitter box into t
Page 31 and 32: 8. Mark a start line on the floor w
Page 33 and 34: Battery Replacement 1. Turn both of
Page 35 and 36: 5. Place the 3v lithium battery in
Page 37 and 38: - Dry the cleaned area with a soft
Page 39 and 40: 3. Humidity The device should not b
Page 41: The footswitches and force sensitiv
Page 45 and 46: 10-bit analog-to-digital conversion
Page 47 and 48: Figure 38: Microprocessor Circuit f
Page 49 and 50: Metric A L M S1 S2 mm. 9.5 35.0 25.
Page 51 and 52: to supply a very small voltage (les
Page 53 and 54: A B C D Figure 45: Male LEMO Connec
Page 55 and 56: Telemetry: Transmitter Set-up Figur
Page 57 and 58: Figure 50: Receiver Circuit schemat
Page 59 and 60: The 418MHz transmitter/encoder chip
Page 61 and 62: Analog Inputs Digital Inputs Figure
Page 63 and 64: 4. Trouble-Shooting Problem Possibl
Page 65 and 66: 4- If no output coming out of the F
Page 67 and 68: 7. If the footswitches and the FSR'
Page 69 and 70: 10. If LabVIEW program is not worki
Page 71 and 72: 13. If the male LEMO connector is n
Page 73 and 74: 16. If LabVIEW program still not wo
Page 75 and 76: Page 75
Page 77: 20. If the circuit is working fine

Biomechanics Gait Analysis Lab - Biomedical Engineering ...

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