where to syphon off voltage from a 25 pin serial? I have a mircocontroller that's looking to be powered by a 5v source.

I am trying to 'cypher off' some of this power from a 25 pin serial port, which is being powered by a constant power source.

Are there any pins that could give me that sort of voltage, or enough to power the board?



Please note, I'm not an electrical person at all, and so hope this is actually possible (otherwise my 3 months + program's work doesn't really add to anything).

I've tried a 9v battery, but it didn't seem to hold its charge? 

I'm reading these labels going "what the ..." so you can probably tell coding the board wasn't the easiest, either.

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I would like to clarify this is an existing serial lead
I understand this may be deemed verging off topic, but due to the need to 'power' a microcontroller, I thought this could be answered here
If this isn't possible, (as an alternative, possibly) would a 9V/battery be able to power this board reliably for around 2-3 weeks?
You should be able to use pin 7 for negative, 9 as positive, this gives you 12 volts.

YOU MUST NOT HOOK THIS UP DIRECTLY to the arduino, connect it to a plug for the power jack (right of the USB connection).

If you are using a USB -> serial adapter, then the voltage may be 5v, but don't count on it.

Of course, USB is always going to be better!

PS - if you draw more power than the serial port is rated for, you will probably destroy the card. In most cases, this will be the motherboard. You are unlikely to be able to find out what it is rated for (look for Amps or A, or milliAmps  mA, or microAmps uA). The Arduino (with NO inputs or outputs, and idle) running from a 9v battery will draw about 50 milliAmps.