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

Direction (Degrees) Resistance (Ohms) Voltage (V) 033k2.53 v k1.31 v 458.2k1.49 v v 901k0.30 v v k0.595 v k0.408 v k0.926 v k0.789 v 22516k2.03 v k1.93 v k3.05 v k2.67 v k2.86 v k2.26 v Table 1: Output Voltages for Wind Vane Positions

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:

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:

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 – Wikipedia H-Bridge Graphic – Wind Sensor Data Sheet – eather%20Sensor%20Assembly..pdf Flex Sensor Data Sheet – LEXSENSORREVA1.pdf