Transcript wind sensor
ECE445 Presentation Smart Umbrella Group 35 : Dominic Antonacci, Jonathan Buie, Martin Miller TA: Cara Yang Objective • • Wheel chair mounted system to adjust umbrella according to wind speed and direction Consists of 3 elements – Wind Sensors – Control System – Motor system Block Diagram WIND SENSOR Wind Sensor Requirements • • • Physical Integrity of Flex Sensors Measure the direction of the wind Measure Wind Speed within 3.5 mph Original Wind Sensor • Non conventional method of wind speed detection using flex sensors Significant outdoor testing required to measure response across wind range (0-25mph) Sensors are delicate and require individual calibration Wind Wind Sensor Challenges • • • Expected Resistances between 10kΩ (neutral), 60kΩ – 110kΩ Small dynamic Range for Resolution of ADC in controller Cup Anemometer and Wind Vane Simple and more reliable Wind Sensor Components • Cup Anemometer – Measure the wind speed – Output Square Wave • Wind Vane – Measure direction of wind – Degree measure corresponds to resistance value – Voltage Divider for A/D output Wind Vane Circuit Voltage Divider • Need to drop Voltage before 1.5 V for ADC in MSP430 • MOTOR Mechanical Requirements • • • Umbrella should be able to withstand 20 mph winds. Umbrella should be able to quickly adjust with changes in wind speed Power should come from a 12V wheelchair battery Motors Chosen Banebots RS555-12V • 12V Brushed Motors • 15A Stall Current • Peak Efficiency • – 6660 RPM – 4.76 oz-in Source: http://banebots.com/pc/MOTOR-BRUSH/M5-RS555-12 Motor Controller I Designed a motor controller to be able to power these specific motors • Drives motor from PWM signal • Capable of driving motors in either direction. • Source: https://en.wikipedia.org/wiki/H_bridge Motor Controller II Motor Controller III Issues With Motor Controller Gate switching times were too fast • Lack of decoupling capacitors • Motor Drivers rated to 12V. Battery can be charged to around 13.8V • MICROCONTROLLER Controller Requirements • Able to rotate the umbrella at least 360 degrees • Able to pitch the umbrella a maximum of 45 degrees. • Can move to any location in range within 2 degrees. • Non-oscillatory output Microcontroller • INPUT from sensors • Wind sensors • Positions sensors • OUTPUT PWM signals • Use PID to determine duty cycle Microcontroller Build and Testing • PWM output • Use serial to set period and duty cycle • Measure output on scope • Measure frequency • Measure duty increment • Pure hardware interrupts a must for high frequency PWM Microcontroller Build and Testing II • ADC Input • Setup ADC to read 4 channels in sequence • Use a potentiometer as a test input and write output to serial to verify • Known good inputs and outputs eased testing of internals. PID Issues • • • Gain tuning Discrete Measurements System Identification What’s NEXT Future Work • • • Redesign circuit schematic Improve PCB layout Redefine Requirements – Meeting requirements did not mean circuit functioned as expected Conclusion • • In all, we created a hands free device for use on a wheel chair Future improvements – Field Testing – Potential handheld implementation – Lower Cost of system – Wind Sensing Accuracy Special Thanks • We wish to thank the ECE Machine Shop for their time, advice, and effort towards the construction of the mechanical structure. • The members of the Electronics Shop for PCB construction and help with overall – Our project would not have looked nearly as impressive if it wasn't for their massive assistance! • Special Thanks to Cara Yang our TA as well as Dr. Makela and Dr. Oelze Works Cited • Banebots Motor Graphic – http://banebots.com/pc/MOTOR-BRUSH/M5-RS555-12 • Wikipedia H-Bridge Graphic – https://en.wikipedia.org/wiki/H_bridge • Wind Sensor Data Sheet – https://www.sparkfun.com/datasheets/Sensors/Weather/W eather%20Sensor%20Assembly..pdf • Flex Sensor Data Sheet – https://cdn.sparkfun.com/datasheets/Sensors/ForceFlex/F LEXSENSORREVA1.pdf