An other robot built a few months. This one detects collisions, go backward and change direction.
Once again, no micro-controller inside... but it's the last time I swear ;) (it's more difficult and requires a lot of time for the very beginner that I am)
This time I wanted to do something more flexible. The motors are driven by PWM.
I got inspired by a french book : "Petits Robots Mobiles" by Frédéric Giamarchi (yes, him again ;)
The motors card has 4 outputs for the 2 motors and 4 inputs : 2 for speed (one for each motor) and 2 for direction (for each motor). The signal is generated by a LM 324 and the current is amplified by a ULN 2003. Then, 2 relays drive the motors.
The "brain card" has 2 outputs to send the direction of the motors. One input indicates when a colision occurs thanks to a micro-switch. It uses 2 timers (NE 555) and a resistor to adjust timing. The circuit also involves a TL 431 : when the voltage reaches a a certain threashold it lets the current go threw, this way, it lights a LED when the battery is low.
When a collision occurs (switch activation), the 2 timers get activated and init a reverse movement of a different duration for each motor (to change robot's trajectory) and then, the forward movement starts again.
The robot uses a 7.2V battery which is regulated by a resistor, a Zener (5.6V) and a transistor to stabilize voltage.
(the ability to change the motors' speed by the "brain PCB" is not used in this robot)
The home made collision detector ;)
Finished robot !
I tried to power on again this robot for a video, but sadly, it doesn't work anymore as it was supposed to (it's more a bulldozer than a mole now ;)