There are times when GPS is not enough or available, such as when inside building where GPS signal is blocked. The aim of our project is to get direction using an alternative source: Light. It could be sunlight, flash light and etc. To achieve this, we arm two sides of our vehicle (wheelchair) with two photo resistors (inside homemade coffee cups). The sensed signal tells the direction of light. Then the vehicle driven from MSP430 with PWM control make turns accordingly based on the sensed signal comparison. One cool part of the project is that our code runs real time on Android devices runnning basic, communicating with MSP430 through bluetooth. 


  • Yingzhe Hu
  • Minjie Chen
  • Jalal Uddin
  • Special thanks: Leonardo Estevez


  • The EYE: Two photo resistors serve as the eye of the wheelchair. To better collect light, we arm the photo resistors with homemade coffee cups (see image below). The photo resistors are biased with fixed resistors for voltage readout. For better SNR, the fixed resistor value is selected roughly the same as photo resistor value under ambient light condition. The sensed voltage signal is feed to pin 6 and 7 of MSP430 for A/D conversion.



  • The  BRAIN: The brain is the Android device that runs code in real time. Every 100ms, the digitized sensor signals from pin 6 and 7 are first sent to Android device through Bluetooth radio on PCB. Then the Android device make comparison of the signals with certain threshold. Finally, based on the comparison results, the decision of turning left/right or stay still is sent back to MSP430 through Bluetooth.


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  • The ENGINE: We equipped the wheelchair with two differential motor as the engine. The power of the motors are drawn from two power FETs on the PCB. These power FETs are driven from two PWM output of MSP430, pin 2 and 14. The level of the PWM output, which determins the speed and direction of the wheelchair, is sent from Android device as described in the BRAIN part.   


Demo Video: