Thursday, October 2, 2014

Uncia Electronics -- In Depth

I haven't seen this in a lot of other places, so it's going here!

The Uncia's electronics are (like the rest of the machine) and clone of Sedgewick's electronics. They comprise of a Teensy 2.0 and a single Pololu A4988 stepper driver. Also included is the smallest, most adorable 12V 1A power supply.

The two boards are mounted on a very simple circuit board.

Yes, that's all there is to it. Click the images to see a close up

It's a bit difficult to see all the connections. I've recreated the board in Fritzing.
This is a simple version -- It just shows what Teensy pins go where. Note that the LED shown is the signal LED that is on the Teensy itself.
Now for the real deal:

This is (I believe, unless I screwed up) the full breadboard for the Uncia.
Please note that Pin 10 is tied to a +5v. I'm not sure why this is the case (Since Pin 10 isn't even used in the firmware), and it doesn't make sense from a circuit design standpoint. I'm assuming it's a mistake. If you're ever pressed for pins enough to need number 10, it's easy enough to slash the thin trace that connects the pads.

Anyways, it's clear that the Teensy isn't being used to its full potential. This is actually pretty nice, as it allows for upgrades to the printer without having to swap the electronics!

With these upgrades in mind, I scribbled out the layout of the breakout pads that litter the board.

The layout of the three pads that line the board.
I don't like how the 5V pin is in between the GND and Signal pins -- it means that you can't just use a simple 2 pin BLS connector. C'est la vie, I suppose.

When programming new firmware in the Arduino IDE for Teensy (Teensyduino), just keep the following image in mind:
The numbers closer to the board are the pins called by Arduino code.
Note that pins 7 and 8 are both reserved for Rx and Tx -- if you attach inputs to these that force a HIGH or a LOW, you won't be able to upload new firmware.

All of this information will be used in the improvement of the Uncia firmware (Or should I say the Sedgewick firmware...). Check it out!

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