Some assistance needed / Prize for the answer

I have an arduino-controlled Etch-A-Sketch which draws an image from a bitmap. (Details here: joetcochran - sketchduino)

However, when I run it, one of the chips on the arduino gets extremely HOT and I'm starting to get concerned that I'm going to damage my arduino.

If you go to this link, you can see a rough schematic of what I've put together, along with an image pointing to what chip is getting too hot:
http://www.softwaremill.org/sd/

Here is a link to the motor datasheet, if it helps:
http://www.softwaremill.org/M11-17D-4101A.pdf

The first person to give me some good, specific advice regarding what to do (e.g. add resistors, capacitors, etc.) about the heat problem will earn themselves an etch-a-sketch portrait of their favorite jpg.

Thanks a bunch!
Joe

...will earn themselves an etch-a-sketch portrait of their favorite jpg

FedEx will have to be extremely careful with that package!

Andrew

haha - now obviously i would make the portrait permanent by emptying out the excess aluminum powder.

I think that chip is the on-board voltage regulator of the Arduino. If it's getting too hot, that means that you're drawing too much current from it! You need to change the wiring of your system so that the high current stuuf (the motors) gets its power directly from the power supply, without passing through the Arduino. I'm not sure where the "4.5V 1A" power supply is connected to the board, though. Surely 4.5V is not enough to run the Arduino reliably? Anyway, that power supply need to go directly to the yellow and white wires of the stepper motor(s).

Really nice results on the Etch-A-Sketch, well done!

Bingo! your motors require a lot of current as well. The datasheets call for 1.2 A per phase.

Also since the regulator has a votlage drop of 1V you need atleast 7V on your power supply to power it correctly.

Also for this regulator it can output a maximum of 1.4A. And at this point it heats up a lot. Especially due to the fact that it is not being powered sufficiently.

So it boils down to this, you need to change your power supply. Something like 7V 2.5A should be good. If you find yourself drawing more than 1.4A of current (which you may be doing if both your motors are operating at the same time), you might need to change your regulator as well.

EDIT: some more info:

the regulator: http://www.onsemi.com/pub_link/Collateral/MC33269-D.PDF

reccomended supply: http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=T959-P5P-ND

reccomended regulator:
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=LM1085IT-5.0-ND

I noticed from your google page you switched from usb power to the wll adapter so first stick with usb to the arduino. This power can be used to supply power to small sensors like pots or ir sensors but not to power motors. It is best to keep the motor power supply discrete from the arduino or else you risk burning your $30 board.( what is happening is you are supplying 4.5 V 1A into the arduino’s voltage regulator which can only let out .5A so when you try to pull 1.4 A out per stepper motor the chip heats up and eventually thermal shutdown aka smoke will occur).

To fix this:

1: un-connect the wire going into the ardunio 5V.
2: get a barrel jack adapter for the power supply (or cut off the end)
3: connect the positive from the supply to the Vcc pins of your h-bridge chips.
4: connect all the grounds together( this is important for the h-bridge to work it needs a common ground with both the arduino and the power supply.

this should make it work without any heat problems but…

  • the motors are rated at 3.6 volts but this shouldn’t be a problem if you don’t leave them on.
    -are you leaving the motor’s always on( stalled). i built a plotter recently that can’t run both motors at once off of one supply. To fix this after i moved each motor i sett all output pins to low. otherwise even when the motor isn’t moving it is using current to stay stalled.
    -If you are moving both motors at once you really need a supply that can handle 2.8 amps.

also can you post your code? I built a plotter to make circuit boards but am still working on the code to read the gerber files. This would be a fun adaption for my project without much alteration to your code

We have a winner! Congratulations to clifdweller, since his solution didn't require me to purchase any new components.

Thanks, everyone