This is something I worked on over the course of 2 weeks. It was meant for my final project in my Engineering First Year class. Its a 556 Based light seeking robot. I can’t take full credit for the idea because I borrowed the schematic from an instructables and modified it a bit to use the 556 and along with a few other changes to make it more stable.
My Altered Schematic:
Take note, It has been a while since I used Kicad so my schematic might not look very neat:
Project Motors and Wheels- Amazon
Long Single Side PCB- Amazon
Light Dependent Resistors- Amazon
556 Timer – Digi-key
Project Wires – Amazon
2x NPN transistors – Amazon
4x 10k resistor – Amazon
2x 0.01uf Capacitors – Amazon
2x Flyback Diode – Amazon
9V Battery- House Hold
Hot Glue – House Hold
This project is pretty straight forward. Follow the Schematic and make sure to solder the components to the board. From there use the wire to jump the connections. Keep the LDRs in the front and the wheels and battery in the back. The PCB I linked above has 2 rails on both side for power. Use Super glue to glue the motors to the back. Once they are stuck on, attach the Wheels that came with the motors and there you have it.
How it works:
This robot requires 2 555 timers in Bistable mode. Because the 556 is just 2 of them in a single package you can see how easy it is to substitute it. The trigger of each 555 is connected to the LDR. When light hits the LDR, the resistance decreases. Causing the output of the 555 to Increase. The output is connected to the base of an NPN transistor.The collector and emitter are set between the battery and the motor. So basically when the light is on, the timer puts the NPN in an active state turning the Motors turn on. When the light is off, the transistor goes off causing the motor to turn off. Another thing I added, that the original design did not have, was a flyback diode across the motor. This helps protect the circuit from reverse current after all we don’t want our transistors fried.
Example of a Flyback Diode: