Wednesday, April 23, 2008


Darwin@Adrian goes Arduino

I've finished the hardware work on upgrading my home machine to Arduino control. I've done a few hacks:

  1. I distributed the circuit boards round the machine next to the devices they control. This actually cuts down the wiring cross-section, if not number, in the sense that - for example - two power wires and three signal ones go to a stepper controller, as opposed to four power wires from it to the motor. Using ribbon cable for the signals keeps it neat.
  2. I added 78L05 regs to the stepper boards so that everything only needs a single 12v supply. I just soldered them into the same holes as the power connectors, which I made 2-way screw connectors. There are already smoothing caps on the boards.
  3. I reconnected the 5v input to the extruder motor controller board to its internal 78L05 to make a 5v output on it. This, and the ground connector next to it, are just at the right pitch to solder the little thermistor PCB on there facing backwards. It therefore gets a local 5v supply, and just needs a single signal wire to take the voltage from the potential divider to the Arduino analog input.
  4. I don't have axis max optoswitches. If you leave them off, pin Analog 2 on the Arduino (Z max) needs to be grounded. X and Y seem happy open-circuit.
Everything checks out and seems to be working in the sense that I can drive the motors about. I think I still have to do a bit of debugging on the heater/temperature sensor...

Postscript: Number 3. proved to be a Bad Idea. The temperature sensing works a lot better if you drive the thermistor board off the Arduino's 5v line...

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I've thought about moving over, but I think my generation 1 electronics will do me good for a little while yet. I've seen bluetooth arduinos (, they are very expensive right now but will hopefully get a bit cheaper once more widespread. I like the idea of being able to place my reprap anywhere in the house (with power) and let it get on with building out of the way.
Looks beautiful, Adrian!
In the eye of the beholder...

Yes - a wireless RepRap would be pretty cool. Of course it might spontaneously spring to life and start printing a vase that just matches the one you know your neighbour broke yesterday...
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