Power Supply

Is it possible to power an arduino diecimila by connecting it to another arduino diecimila?

I have two that I'm using for a project. One of them is being used for USB communication and the other for MIDI but I don't want to have to use an external power supply and make another hole in my enclosure case.

Is this possible? Or advisable?

You should be able to bridge the +5v and Gnd from one board right over to the other with no problems that I can see. If you start drawing a lot of power, obviously your power supply needs to be able to source enough current for both boards.

The problem here is the voltage regulator on the board powered by USB.

This voltage regulator can only supply up to 200 mA without serious heatsinking.

Also a USB port on a PC can theoretically supply up to 500 mA, but you are not guaranteed that any given PC's USB port will actually do so.

So you should do some tests to see how much current each of your boards use, and do the math.

The problem here is the voltage regulator on the board powered by USB.

I don't think that is true. There is the USB and the voltage regulator, there are septate. The 3V3 line does come from a regulator inside the USB chip but when powering the arduino through the USB the power does not go through the regulator. Check out the schematic.

Forgive my ignorance. I'm new to all of this. How would I bridge the two?would I take the power? Could I solder a power connector to the 5v and ground pins of one Arduino and connect it to the second? Is there a more elegant way of doing this?

I'm with Grumpy on this one, it's highly doubtful you'll run into any problems running two arduino's where one arduino runs fine.

I think the regulator issues are based more on the voltage... I've ran nearly 400 ma for.. I don't have an exact time.. but long enough to get warm. I'm guessing like 20 minutes ish? Was testing some servos.. and there was almost no heat dissipation.

But once I plugged the Arduino into a 9v Regulator (regulated, constantly puts out about 8.75 when it doesn't have a load) and did the same test.. got fairly warm very quick.

Just put the 5v line to the 5v line on the arduinos, and the ground to the ground. That'll power them both. Assuming one actually has power of course. :D

Just curious though, what's the reasoning behind trying to connect two boards? (they are boards right? not the chip alone?)

Ups, sorry

i got the regulator mixed up with the USB power, that is rubbish of course.

Thanks all. Basically Ive built an arduinome and have added an extra arduino to handle six pots for midi control. I had looked at multiplexing options but it would mean modding the OSC router as the current solution is buggy and I didn't want to add an external psu to keep things simple.

One of the arduinos is driving 64 LEDs and the other will just be converting the pots to midi info. Think it'll be fine?

Think it'll be fine?

Yes. Although to keep it simple I would have only used one Arduino. It could handle 6 pots and the LEDs easily with just the addition of a shift register.