Robot requirements

This blog is about the creation (birth) of a new robot friend for Joseph, my son who is very lonely.

The main requirement is that it doesn't bump it's head on walls, so when it gets near a wall, it must turn around and go the other way.

It's brain will be a PIC microprocessor and to simplify the programming a PICAXE will be used. This was chosen so that Joseph can lean to program his new 'brother' using the simplified IDE that comes with it. Other than that, along with much larger programs, it's the same PIC microprocessor.

The little lad will have new legs in the form of wheels, these will be powered by continuous servo motors or stepper motors. The reason for this is because if normal DC electric motors are used they will have to be geared down which would be a bit of a pain and require lots of extra hardware. The servos can just be told to rotate in a certain direction at a certain speed and that's it. Once they are mounted they are good to go.

The little fellas eyes will be ultrasound sensors, these will alert him to the proximity of objects and allow him to take evasive action.

His body will be made of metal Meccano which used to belong to grandpa (my dad).

So far we have the 2 servos held in place by some Meccano, a PICAXE prototype board (on the right), two battery packs - one for the PICAXE and one to power the servos and a small bread-board to make the various connections.

 The PICAXE prototype board came with a Darlington array to drive motors etc. but this was not needed to control the servos, in fact it made it impossible to drive the servos from this board. In order to get it to work I replaced the Darlington chip with a 330 ohm resistor array that connects to all the the port B outputs from the PIC.