Robots
I've done some experiments with low-cost robotics platforms. I found that Tamiya have cheap kits (they used to be cheap years ago, when I did this) which are good for this, namely the Tamiya 70068 Wall Hugging Mouse kit and the Shovel Dozer if you need dozer-type traction! I modified the wall hugging mouse, adding larger model airplane wheels to allow it to operate on carpet, and gutting the "electronics" (if you can call a single microswitch "electronics"), replacing it with a PIC16C84 microcontroller, L293D H-Bridge DC Motor driver chip (actually 2 piggy-backed to supply more current). A basic TTL oscillator running at 40kHz drives 2 near-infrared LEDs and is controlled by the micro. The micro reads a Sharp infrared remote-control sensor to see if any objects have bounced any of the infrared light back, thus forming a "radar" object detection scheme. The microcontroller then switches the motors accordingly. The rest of the smarts are in the software. One day I'll get around to putting circuit details and maybe some software routines on here.
OK, so it isn't anything like the Wall Hugging Mouse anymore as I also gutted the motors and worm drives and replaced them with the Tamiya Dual Motor Gearbox kit. This provided much needed grunt and is controlled by the electronics described above.
A modified Tamiya Wall Hugging Mouse.
Top right is the Sharp infrared sensor atop the batteries (1x 9V and 4x AA)
The Tamiya Shovel Dozer kit has good traction, can drive over things almost it's own height, and has plenty of room on the chassis for electronics. It comes with the dual motor gearbox, which you can also buy separately. It was cheap back when I bought it.
Closeup of the mouse controller. I found a single L293D got very hot so I piggy backed 2 of them to double the current handling and soldered a heatsink across the 2 centre ground pins on each side. I got the heat fins from an old audio chip, but any old aluminium cut to shape will do.
Written by Greg Newton in Sydney, Australia. If you want more information, you can contact me at greg dot newton dot oz at gmail dot com (written like that to avoid spam bots).