RepRap: Blog

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...

Labels: arduino, darwin