Robot hand PC interface

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Robot HandI guess my love for robots started when I was in eighth grade or so. It must be the tele-series ‘Battle Star Galactica‘ and continues visits to my school library’s, ‘science – reference only’ section. The various colorful sci-fi dreams kept my head full. I had sketches of weird machines all over my textbooks! The first useful ‘gadget’ must have been a ‘water powered dish washer’ back in late ’80s. The idea was never realized, unfortunately. And then I designed my first character ROM using mechanical parts. After discovering digital electronics, I started laughing at my old ideas! Jeez what a waste of brainpower.

While I was in Sharjah, in 1991, I came across a 5-axis robot hand in a toyshop. They had only about 2 or so units and were stored in a place where no one can see unless you are searching for it. As soon as I saw the yellow hand on the cover, I jumped at it and bought one right then. It’s made by QuickShot and can be operated by two joysticks (You know the old Atari type, mechanical buttons). After reverse engineering the internal circuit I wanted to control the robot hand with my PC (then, a state of the art Hyundai PC-XT, with 1MB Ram and two 360K floppy drives!).

Internally, the hand uses two-transistor bridge circuits to turn motors clock and anti-clock wise. There are totally 5 motors. The only trouble with this gadget is that there is no way to find the present location, since the motors are just plain vanilla DC type. After all, this is a toy!

My first try was to go all solid state. I tried using CMOS (analog) switch approach. Couple of 4016s and the PC LPT port should do it, so I thought. I built a good-looking PCB for this. And it all came very well, just the way I planned. But, then I figured the motors were drawing more current than these tiny little CMOS chips could handle. I thought of switching to mechanical relays.

Enter ‘Aromat’, PCB relay. These I found while I was shopping in Sim Lim Tower (the famous place for electronic junk in Singapore). This little relay was exactly what I was looking for, 5V, 16 pin DIP compatible, and handles 2A at 30VDC! I used a ‘Vero’ board for this prototype. The circuit works todate without a hitch!

The ‘big’ board next to the relay board is my ‘all purpose buffered LPT interface’; specially designed for experimenting and interfacing with LPT port.

robot hand Robot controllerRelay board relay board closeup

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One thought on “Robot hand PC interface

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