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By Dalorin
For my project I need to be able to drive several electro magnets (just large hand wound coils). I'm planning on using darlington arrays to sink the current through the coils.

I will also power my arduino pro (from sparkfun) with the 7.2V nicd battery pack.

I know that I need to place a 500uf capacitor across the battery and a diod to stop backflow so that the draw from the coils do not drop the logic supply too far. And I also know that the Arduino pro has a 5v regulator built in, but what I'm worried about is the current.

The question is this. What precautions in general do I need to take when connecting a 7.2V nicd pack (like the kind for remote cars) to the arduino? Do I need a current limiting resistor? I do not want to overheat the regulator. Can I connect it to the JST battery connector on the Arduino Pro's board? I want to make sure that I do this correctly. If you have any experience with this I would greatly appreciate any help.

Thanks in advance.
By Liencouer
If you have a schematic to post, that would help us verify what you're trying to do.

As for the regulator, so long as you're not driving the coils from the regulated 5v supply, you probably dont have to worry about damaging the part.
By krphop
You don't need to current limit the arduino, it will only draw what it needs to run. You can attach the 7.2V battery directly to the VIN jack, which will power the regulator on the Arduino.

You need to be very careful where you place your diode for reverse current from the coils. You want to do this right at the coil, not just back at the battery. If you do it back by the battery, every other component in your circuit will get hit with the reverse current spike.
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