Touch-Free Remote Control

1. 11 Fall Touch-Free Remote Control ECE 445: Senior Design c Team 18 Mark DiVito, Sungjoon Park

2. Objective • Design and build a user-friendly touch-free remote control • Device will sense user hand movements and control various parameters on a TV • Ability to change the channel, volume, and turn the TV on and off • No buttons!

3. Features • Light-weight and portable battery-powered transmitter • Change channels, volume, power • Precise hand motion detection and interpretation

4. Benefits • No need to use complex remote buttons • Does not need line-of-sight to TV because of RF transmission • Can use the remote with greasy potato chip hands • A new and unique way of TV interaction

5. Original Design Transmitter

6. Original Design Transmitter

7. Original Design Receiver

8. Original Design Receiver

9. Voltage Regulator 120Ω Vout= Vref(1+R2/R1) +IadjR2 Vin = 4 x 1.5 = 6 V 3.03 V nominal output 166Ω

10. Proximity Sensor

11. Proximity Sensor

12. Phototransistor Amplifier • No hand: phototransistor conducts, Vout = VOL • Hand: no current, no voltage drop across R2, Vout = VOH 20kΩ 6.2kΩ Vout 220kΩ

13. Phototransistor Amplifier • Phototransistor current spec range 100nA to .5mA • Physical design: • VOL = .22V • VOH = 3V • Can interpret as logical 0 and 1 • Detects light 1ft away 3V 0.1V 200uA 0uA

14. Input Translation • MSP430: receives analog input from sensors • Hand detection based on threshold voltage • State machine with timing requirements • Serial data output to RF transmitter

15. Input Translation Tests and calibration: • Detection distance from proximity sensor • Appropriate speed for hand motions • How fast are repeated commands sent

16. RF Transmitter and Receiver • 434 MHz carrier frequency • Spec is 10,000 bps

17. RF Transmitter and Receiver • Test: max transmitter driving frequency where received data is valid is ~40kHz • Range: 10ft with no antenna, ~100ft with whip style external antenna • 20kHz square wave driving transmitter • 2V/div • 50us/div • ~25us delay

18. RF to IR Translator • Arduino Uno: receives RF serial input from receiver • Decodes the serial input and determines desired command • Drives IR LED to send command to TV

19. RF to IR Translator • Test: IR LED output within 5% of RC5 protocol timing spec • Spec is 889us length for one bit, measured 890us length, 0.11% difference • dx = 890 us • 2V/div • 500us/div

20. System Performance • The remote’s sensors should respond to a hand approximately 1 to 2 inches away • The time from a user input to the IR transmitter sending a signal to the TV should be less than 200ms • No information loss • dx = 186 ms • 2V/div • 50ms/div

21. Challenges • Constructing the case • PCB • Sensor alignment and placement in the case • Four AA batteries instead of two • Determining what type of sensors to use

22. Conclusions • The final product worked as intended and provides the user with a reliable touch-free remote experience • The system meets all timing and reliability performance requirements • Each block was successfully tested individually as well as the system as a whole

23. Recommendations • Add more phototransistor sensors • More sensors would add the ability to support more gestures and commands • Better methods to keep sensors aligned in the case • Higher quality reflective proximity sensors

24. Questions?