TIP 120 Driver

Heya,

I've recently started a quest to try and convert all of the RepRap electronics to something that is Arduino compatible. I've made good leeway on the stepper driver, motor driver, and yesterday I started to tackle the TIP120 driver. I'm not sure if that is the best name for it, but essentially it is a PCB with 3 PWM inputs from an Arduino that are each run through their own TIP120's in order to drive various components (heater coils, fans, etc). The circuit seems pretty basic, and I followed some guides on the internet, such as Tom Igoe's stuff. I do have some questions however:

  1. Would anyone mind looking over my design? Its in Eagle, and located at https://reprap.svn.sourceforge.net/svnroot/reprap/trunk/users/hoeken/freeduino-power-transistors/

  2. Power and grounding. We generally use PC Power supplies to drive our electronics, and I've placed a standard molex disk drive power connector as the connector for power in. It provides 12v, 5v, and GND. How do I integrate this with Arduino? Do I connect the grounds together? Can I use the 5v from the PSU to drive Vcc levels? Should I connect the 5v from Arduino to this 5v? I really like the disk drive method because it allows me to simply plug the power supply directly into the board and I don't have to make any cables or whatnot.

  3. what would be a better name for this? PWM Driver? Power Transistor Driver? I'm just not sure what to call it.

edit: oh yeah, i forgot to mention that this board is licensed GPL.

It provides 12v, 5v, and GND. How do I integrate this with Arduino? Do I connect the grounds together? Can I use the 5v from the PSU to drive Vcc levels? Should I connect the 5v from Arduino to this 5v? I really like the disk drive method because it allows me to simply plug the power supply directly into the board and I don't have to make any cables or whatnot.

I'd connect the ground and 12v to the Arduino. The Arduino's voltage regulator will give it the 5v it needs.

Nice idea using Molex connectors btw.

Cool. I’ll probably end up wiring the Arduino up take its power off the external dc connector which i’ll connect to my PSU. from there, I’ll run 5v, GND, and the inputs to the board from the Arduino. I’ll run 12v + GND to the board via the Molex connector, and I’ll connect the GND from the PSU and the GND from the arduino there as well.

Does this sound like its the best way to do it? I’d like to minimize noise and such, but I’m not really familiar with techniques to do that. I’d also like to minimize the number of wires that need to be run between boards for simplicity’s sake.

Thanks for your help!

Yay! I breadboarded this circuit (well, one of the 3 TIP120 driver circuits) and it worked great! Man its so awesome to come up with a circuit and then to easily interface it with a microprocessor. Thanks Arduino!!!!

Here is the Flickr set where I uploaded pics of the breadboard: http://www.flickr.com/photos/hoeken/sets/72157602201702876/

Now that I've had a successful, 'real-world' test, I think I'm going to go ahead and order a batch of the boards to test. I'll be getting way too many of them, so if anyone wants one to play around with, shoot me an email. I think for this first round, they'll cost about $5 / ea for a PCB, and probably another $5-$10 to stuff. Not too shabby for a 3 channel, 5A PWM driver that is easy to interface with Arduino.

ps. thanks to ladyada for their awesome breadboard shield. built it today, and i freakin love it already.