Dale's Homemade Robots

Light Seeking Spinner

by Dales Homemade Robots
Oct 31 2006

Above is a picture of an experimental robot that spins continously while moving towards a bright light source. It doesn't have a microprocessor to control it.

Its control system is made of 3 CDS photocells connected to MOSFETs which operate 3 DPDT relays. The relays control the direction of the motors. When the light is below a preset threshold the motor runs forward. When the light level exceeds the threshold the relay operates reversing the motor. Each motor has a dedicated relay, MOSFET and photocell. See schematic below.

The motors are wired in series. When one photocell detects light above the threshold the relay reverses the motors wires which causes it to reverse. Because the motors are wired in series the current flowing through all three is the same. When one gets reverse polarity it needs more current than is available and stalls while the other two speed up. The robots body pivots around the stalled wheel which drives it towards the light source. Each wheel stalls at the same angle relative to the light source and the robot slowly moves to the light. If the polarity to all 3 motors is reversed the robot will move away from bright lights.

Demonstration video

Eventually I plan to hook it to a microprocessor and devise a directional antenna for reception of radio control data and a reference heading. IR control is also possible. I should be able to control it with a joystick. The processor would shift the phase and duration of the motor reverse interval relative to the reference heading to set direction and speed. This may eventually lead to a combat robot for Dragon Con Robot Battles.