Front of Gerald

Back of Gerald

I had the urge to build a robot for a few months but exams and other projects go in the way. I’d formed a basic plan in my head and made some sketches in my notebook. Finally one Sunday morning I got him started.

His basic body of two servos glued together with a 3xAA battery box on top came together quickly and by evening a little test program had him rolling around.

the first sketch of gerald

Two weeks later and many evenings work I can say his hardware is complete and his software nearly done (he can always be reprogrammed so his character is never completely finished). There were lots of small problems along the way but most were solved within a day and 95% were silly mistakes on my part. Half the reason I made Gerald was training for future projects. He doesn’t do anything particularly fancy or have a special skill but in the future I’d like to make a robot does. What I’ve learned from making him is invaluable training foe the future. He is also the ideal test-bed for new ideas.

He is not a tiny robot but he is pretty compact. The wiring is a bit untidy but it is possible to make fixes if something breaks. Major respect goes to anyone that makes robots smaller than Gerald, it would take some considerable skill and planning to do.

beginnings of Gerald

His feature set is not too shabby, this is what he can do:

• IR Following
• IR Avoidance (can’t actually do this yet because I’ve not programmed it!)
• Light Following
• Light Avoidance (can’t actually do this yet because I’ve not programmed it!)
• Blind Mode (relies on bumper switches)
• Remote Control

His Inputs:

• DPDT (Double pole, double throw) switch - electronics and servos
• 3 bumper switches – whiskers + bottom bumper
• DIP switch – mode selection
• Push Button – pause/activate
• 2 LDRs – visible light eyes
• IR Phototransistor - infrared eye
• IR receiver – remote control
• 3.5mm socket – programming port

His Outputs:

• 2 large servos – left and right motors
• 1 small servo – swivel head left and right
• 3 leds – servo status , electronics status  and microcontroller controlled led
• piezo speaker – sound
• 1 IR Emmiter - for IR eyes

His brains are a PICAXE 20X2 microcontroller. It’s a brilliant chip and I never managed to use all the inputs or outputs. With 4096 bytes of memory I could also be lazy when programming him, there was no need to optimise space or use the same variable for different purposes.

The design was intended for him to be easily controlled. To start him you switch him on with a slide button. He will then play a little tune, flash the status LED and swivel his head. He then beeps until you a mode with the DIP switches and press the push button. Once in the mode you can pause him by pressing the push button. You can then select a different mode or continue with the old mode.

A standard TV remote can be used to control him when he is in the correct mode. You can manually control him (ie. left, right, forwards and backwards) and you can also select any one of his other modes. You can pause him in remote control mode by pressing a button on the remote.