Powering the Protoboard

blittled

I have another micro-controller board that has regulated 5V and 3.3V outputs and I was wondering if there is any good way to use these to power a Protoboard? I believe directly connecting the 5V to the 5V output of the Protoboard would cause problems with the Protoboard 5V regulator.

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Will work for Propeller parts!

David B

I have a propeller project that's powered with four NiMH cells directly connected to the output of a 5V regulator, supplying the board with power over a range of about 4.8 to 5.2 volts.

I made the project with an old beta spinStudio board that has a built-in 5v regulator which in turn supplies power to a 3.3 volt regulator, probably just like your boards. I didn't want to remove the 5V regulator if there was no need to, and all the research I did found no reason not to connect power this way, so I tried it and have not had any problems after maybe 40 hours of runtime.

It wouldn't hurt to try to locate and read the data sheet for the regulator you'll be using; at least try to become informed, but don't be surprised if it doesn't say anything about using the regulator this way.

blittled

Thanks for the advice. I looked at the specs for LM-1086-5V regulator and it said a short circuit from output to VIN would dissipate through the output capacitor to ground so it should not have any detrimental affects on the regulator. I'll have to give it a try.

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Will work for Propeller parts!

Post Edited (blittled) : 6/24/2010 4:32:29 PM GMT

Miner_with_a_PIC

Be cautious....the data sheet mentions the ramifications of the capacitor on Vout discharging to through the regulator when Vin is grounded. Basically current flowing in the wrong direction through the regulator is what is being described. When you initially connect a supply to the the regulators Vout the capacitor on Vin will look like a short to ground momentarily, so it may damage the 5V regulator. Best to do one of the following...

1) Remove the 5 volt regulator
2) Add the recommended bypass diode from Vout to Vin (1N4002)
3) Remove the capacitor from the input terminal of the 5 volt regulator.

I would recommend item 2 as you will still be able to use the boards 5V regulator if need be.

blittled

Thanks Miner_with_a_PIC. I did notice the diode in the specs and wondered if it was something to be concerned about. For now I'll just use it as I have it set up. Each board individually powered and the ground connected to both boards.

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Will work for Propeller parts!