LED following K’NEX Car

All of us have grown up playing many games and toys, toy cars being one of them. Remember how the little legs rushed to veer the toy to some desired direction to avoid a collision. But, the fun doubles if the automatically avoids one and takes a lucrative path. We are here with one such project. Students from Cornell University have designed a toy car which automatically traces an illuminated path. It is called LED following K’NEX Car after the K’NEX toy car used in making the project.

Here, the illuminated path is made of orange coloured LED strip. The orange color for the LED is chosen due to cost considerations. It emitted light waves of wavelength 615nm. The project uses phototransistors to detect light (of wavelength 615nm) from the Led. The voltage signals from the phototransistor is converted to digital signals using ADC and send to microcontroller ATMega644 for processing. On the basis of the relative position of the car with the illuminated path, the MCU then calculates which motor should move and sends a signal to the opto-isolator telling which motor to turn on. Opto-isolator or opto-coupler is an electronic device designed to provide electric isolation between its input and output. The project uses two motors to run the car and a motor controller circuit from K’NEX. The K’NEX motor controller has a 6-pin port which can be used to drive the two motors. A custom PC replaces the USB here to interface the hardware unit with software control. Therefore, once the software is programmed into the board, it is final and binding. So, testing the software was a significant issue for consideration.

The software design of the car comprises of testing the motors for proper functioning followed by the consequent motion of the motors with phototransistor. A software PWM is used to control the speed of the driving wheel.