Running a ProtoBoard from 12V Battery

Pyrotom

For the project I'm working on, I need to run a Protoboard off a 12 volt battery. Looking around in old threads I found something that said you can just do it, but that the 5V regulator would need a heat sink. I tried that - the heat sink quickly go too hot to touch and I think I fried the whole board.

So I'm looking for a better solution. My current thought is to use a Meanwell 15W DC-DC converter (Jameco part number 155716) which would give me 5v at 3 amps. Does this sound like a good way to go, or is there some better way to run on 12 volts?

If I do use the DC-DC converter, should I leave the LM1086-5.0 mounted, and run through it, or should I strip it off and use the 5v from the converter directly?

Paul Baker

I'm not sure what you did to cause your troubles, but I have in front of me a Propeller ProtoBoard driven directly from a 12V battery supply and soldered our small LCD TV power into ground and the Vin pin of the servo rail selector and had no issues. The 5V regulator gets to 105 F which is within the acceptable range of it's operation. The MLX demo runs for 6.5 hours on a 8xAA pack.

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Paul Baker
Propeller Applications Engineer

Parallax, Inc.

Paul Sr.

You should look closely at BEC's used for R/C cars / planes, etc. They will do exactly what you want and are very robust. Pretty much "plug and play" for what you are looking for.

Rayman

For mine, I used a 7809 to drop the 12V to 9V first...

Ken Peterson

We've used several protoboards connected to 12-14V directly. The 5V regulator does get quite hot, but none have failed or even gone into thermal shutdown. We have fashioned heat sinks on some of them just to make sure. It depends on how much current you use on the protoboard.

Another thing you can do is add another regulator (LM7808 for example) in between the 12v supply and the input to the protoboard. We've tried that before too. Effectively it just gives you another regulator to help dissipate the wasted energy.

If your 5V regulator is getting way too hot with a heat sink, you can usually fix that with a better heat sink (and by getting the regulator up off the PCB).

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
·"I have always wished that my computer would be as easy to use as my telephone.· My wish has come true.· I no longer know how to use my telephone."

- Bjarne Stroustrup

Mike Green

I've had luck using a steel-filled epoxy to glue a finned heatsink to the top of the two regulators. I'm sure it has a high thermal resistance since the heat has to go through the package and the epoxy, but it does help. The epoxy is an electrical insulator though and some of it does contact the tabs where the higher temperatures are present.