Thursday, August 13, 2009

The Spoondriver

Being in search of a way to build repraps, I pondered on ways to remove the need to solder circuits together, and an electric motor or heater driver seemed like low-hanging fruit. Go minimalist, I thought. "What would McGuyver do?" I asked myself. Then a hunger pang led to the thought of the awful cheap spoons in the kitchen, and an evil plan formed.

Well, evil if you're a spoon.

The simple solution does away with circuit boards and solder altogether. Three cheap components here to get from the electronics store: A TIP120 series transistor (121 or 122 is fine), a honking big diode (IN4007 or IN5404 are good) and a 1K resistor (any size, brown-black-red lines on one end). Get some small terminal strip while you're there. All the bits look completely different and have an obvious way round when it matters. If you're smart enough to figure out that the insulation needs to be stripped off the wiring before it goes into the terminal strip, you can build this driver.

Shove the leads in the terminal strip - not too far or you'll stop the wires coming in the other end. This might involve technical things like cutting the component wires shorter. In the pictures, the big red & black wires are +12 volts and ground. The yellow wire is the signal wire that connects to your Arduino, clone or Pinguino. The thin black and red wires connect to the load, in this case a small fan. It matters which way round those fan wires go.

It works. But it needs a heatsink to drive loads of a few amps. Bad news for spoons. Having torn off its head, I filed over the wound, bashed its neck flat, drilled a 3mm (1/8") hole in it and bolted it to the hot transistor. Bwahahaha.

The other stuff is an EasyDriverV3 stepper driver that needs eight wires soldered to it to make a stepper motor move. The cheap little switches will replace the opto sensors. That'll have to do for this round of reprap simplification.

So, spoons, don't mess with me!

Vik :v)