1. General.

Like every robot builder that wants to teach others how to build robots, I have built a sample robot, using parts from VCRs and bought only the minimum necessary to make the simplest robot I could think of. At the time I was using the Nemesis microcontroller, produced by Kronos Robotics, however this was not a good choice for Romania, because import taxes would have made their price almost double. Nemesis is a PIC 16F88 with a pre-programmed bootloader. This feature allows the user to program it from the serial port of the PC through a logic level adapter. Kronos Robotics also provides Athena, a free Basic compiler, lots of sample code and great support. Basic is easier to learn by young people, so I thought it is a good choice for beginners. And Nemesis costs only $12.95. A PIC 16F88 costs about $3, but needs a programmer (the cheapest I could find is $40) and the PBasic compiler costs $99. Too expensive. Now I would use an AVR ATtiny26 and Bascom-AVR for programming, cutting the price to about $15 for the whole project. 

Here is a movie with the robot driving (fast) avoiding to crash into obstacles:

Parts list.

The only parts you will need to buy for this project are the Nemesis microcontroller, the SN754410 motor driver IC, a prototyping board, the LM2940 voltage regulator, a battery box, 18 pin and 16 pin DIP sockets, a 5 pin female socket, a strip of breakable male pins. I also bought a serial lever shifter to program the microcontroller from Kronos Robotics website.

All the other parts you can get from a VCR, but you will need 2 VCRs to get 2 identical motors. You will also need a few cable ties, a couple construction nails, wire, a couple small wood screws and 4 AA batteries. 

On the Electronics  page we will go over the schematic to see how things work.