Bicycle Power Meter I love the bike blender!!!! P16214 Sean

Team Member Roles Sean

Agenda -Current Problem -Systems Architecture -Subsystems -Feasibility -Tests -Bill of Materials -Updated Test Plan -Updated Risk Assessment -Next Steps -Schedule Sean

Problem to Solve A bicycle power meter is a device used by professional and amateur cyclists in order to show the cyclist their power output on the bicycle. The RIT Cycling Team approached this MSD team to provide a power meter for their ImagineRIT bicycle blender exhibit. Their desire is to have this device take the input force from the cyclist and display their power output and calories burned. The current devices on the market which provide these features are not quite instantaneous. There is a lag associated with the time between the rider exerting force on the bike and when the rider receives feedback from the system. The goal of this project is to develop a functioning power meter for the bicycle blender exhibit. In order to achieve this task the MSD team aims to improve upon the communication speed between the power meter sensors and the display in existing devices. This will assist in achieving a more instantaneous system and closer to real-time display. Adam

Systems Architecture Display Out iOS App BLE Luke

Subsystems Bluno Nano Arduino BLE Microcontroller Instrumentation Amplifier INA2126 Renata CR2477N Coin Cell Battery iPhone (Smart Phone) Omega Tee 90 degree Rossete 350 Ohm Strain Gauge Frees cale FXLN8361Q Accelerometer Breakout Board Luke

Feasibility: Power Supply Subsystem Analysis System Components: -Battery (Power Supply) -Microcontroller -Accelerometer -Strain Gauges Circuit -BLE Chip Note: The accelerometer, strain gauges, amplifier, and BLE chip are all powered by the microcontroller which will consume no more than 500mA at any given time. Calculations: -Battery Total Power = (Voltage)(Capacity) - Microcontroller PMAX = (PMAX)(Event Length) PAVG = (PAVG)(Event Length) Luke

Strain Gauge Signal Amplifier Feasibility R1 and R2 represent strain gauges Nominal value = 350Ω Max Δ = 0.35Ω R3 and R4 fixed to 350Ω Need output signal to range from 0V - ~1.1V for the uC ADC Connor

Strain Gauge Signal Amplifier Cont’d Voltage divider equations to determine maximum voltage change after wheat-stone bridge: Need an instrumentation amplifier to provide approximately 2200V/V gain Chosen amp can provide 2000V/V gain if R value chosen to be 40.2Ω Connor

Strain Gauge Signal Amplifier Simulations Connor

Strain Gauge Signal Amplifier Simulations Connor

Tests Sean

Test: Battery Design a testing circuit to simulate a high current draw on the battery Connect the batteries to the circuit and take periodic measurements Plot measurements and compare the results to the manufacturing specs Luke

Test: Strain Gauge The objective of this test is to be able to predict the force that is being applied to the pedal from the strain gauge signal The strain gauge will be mounted to the crank arm to measure bending strain The crankset will be clamped, and force will be applied to the pedal via hanging calibrated weights The amplifying circuit will be used to create a more readable signal from the strain gauge The amplified signal will be imported to labview using a NI Daq device for data analysis. Ian

Test: BLE The BLE capabilities of the microcontroller/phone were tested for functionality and range Luke

Test: BLE Functionality Procedure: Connect uC to phone using Evothings Workbench Verify connection Results: Luke

Test: BLE Range Procedure: Connect uC to phone using Evothings Workbench Once connected, increase distance between devices Continue increasing distance until connection is lost Find max distance by decreasing distance between devices until connection is re-established Measure distance between devices Repeat steps 2 - 5 for specified number of trials Results: Connor

Test: Crankset Layout This test focuses on the Component layout as a mock up. Cardboard cutouts of each components were made and placed on the crankset. The test is used to confirm that each component will fit on the crankset Ian

Test: Crankset Layout Results: All the components fit on the crankset. The proposed layout will be used to make the cad drawings for the full assembly. Ian

Test: Accelerometer Adam The reason for having the accelerometer is to allow for the cadence (revolutions per minute) to be measured. The accelerometer will be placed in the center of the spindle of the crank set for the Power Meter. The reasoning for having the accelerometer in the spindle is to protect it from any damage that may occur when riders are getting on and off of the bicycle or from riders whose feet slip off of the pedals and accidentally kick the accelerometer. Another reason for placing the accelerometer in the spindle is to allow for the accelerometer to be at the center of the axis of rotation so that the only acceleration that it will feel is that which is due to gravity. This will allow for the readings from the accelerometer to be most accurate. To ensure that the accelerometer is giving accurate results it must first be tested to show that it is producing the expected results. The following are the steps to test the accelerometer accuracy: Place the accelerometer, and microcontroller onto a breadboard Connect the output from each axis of the accelerometer to an input pin on the microcontroller After powering the devices, choose one axis (x, y, or z) to isolate. Rotate the breadboard with the devices on it to known angles (0 deg, 90 deg, and -90 deg) and record the output voltage of the isolated axis. Also record the number of bits used for each angle (using Arduino code for the Bluno Make sure that each angle matches up with a particular orientation of the axis with respect to gravity (-1g, 0g, 1g) Repeat Step 4. for the other 2 axes After performing this testing this will then allow the microcontroller to be coded to connect a particular angle with each different voltage that is produced. This test will be verified using the calculations that were done previously to determine the level of degree sensitivity of the accelerometer. Adam

Test: Accelerometer The results from the accelerometer test are as follows: The test produced expected results for the x-axis and the y-axis as compared to the data sheet. The z-axis produced unexpected results which led to performing more calculations. After the calculations it was determined that the z-axis produced values for sufficient accuracy. Adam

Test: Strain Gauge Signal Amplifier Texas Instruments INA2126 Instrumentation Amplifier will be tested to confirm desired gain value Test similar to the feasibility simulations will be performed Circuit from previous slide will be constructed in lab R5 will be chosen to be 40.1Ω to achieve 2000V/V gain Sinusoidal signal will be supplied to the wheat-stone bridge Voltage will be measured at the wheat-stone output (varying input to the instrumentation amplifier) and the the amplifier output Gain will be determined by dividing output/input to confirm desired value Connor

Overall Test Plan Results Sean

Estimated Bill of Materials QTY Price Estimated Bill of Materials Predicted Unit Bluno Development Board 1 $28.95 Bluno Nano Arduino BLE Bluetooth Microcontroller 1 $29.95 Freescale FXLN8361Q Accelerometer Breakout Board 1 $10.63 Omega Tee 90 degree Rosette 350 Ohm Strain Gauge 1 $60.00 Renata CR2477N Coin Cell Battery 2 $3.94 Instrumental Amplifiers 2 $3.15 Current Shipping Cost $25.12 TOTAL PRICE FOR PREDICTED QTY $168.83 Sean

Current MSD Bill of Materials TOTAL BUDGET AVAILABLE = $1000.00 TOTAL PRICE FOR QTY = $162.07 EST REMAINING BUDGET = $837.93 Sean

Housing concept Ian

Risk Assessment (FMEA) Ian

Next Steps Test battery Test mobile app Finalize housing design Create dimensioned drawings of complete system Complete design documentation Edge is up to date MSD II plan Adam

Schedule Adam

Thanks!