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x88x
06-29-2011, 07:30 PM
With the purpose of the battery being cut off when I connect the DC input. Since normally-on transistors are hard to find and expensive, I threw this together with what I had on hand (also why I'm using PNP transistors instead of NPN). I just wanted to get a sanity check; make sure I'm not completely off base.
http://i428.photobucket.com/albums/qq3/x13931x/powerSwitch.png

x88x
06-30-2011, 04:22 AM
..ooops...yeah, so I realized I screwed up the transition from paper to Eagle the first time...this is what I did.
http://i428.photobucket.com/albums/qq3/x13931x/bat_cutoff.png

EDIT:
..aaand, I just thought to actually check it, and apparently I had it right the first time except for the output polarity. I forgot; my system crashed and I lost that part of the circuit that I had been working on, and when I rebuilt it the first time I screwed it up... :hurt:

Konrad
07-06-2011, 01:28 PM
It looks okay to me, assuming the semiconductors have sufficient ratings to handle combined (BATTERY + DC_IN) voltage and wattage ... it looks like it's only a 5V circuit anyhow, I don't understand why you're aren't just wiring BATTERY and DC_IN in parallel through a 7805 or similar part.

x88x
07-06-2011, 10:30 PM
9V circuit actually. The idea was to have 0 draw from the battery, which is why I thought of a cutoff circuit first, but yeah, come to think of it a reulator would probably be a better idea. ...I didn't have any of those lying around though. :P

crenn
07-07-2011, 11:54 PM
Or just have the DC IN at a higher potential of the battery and a protection diode, although that could use other issues *whistles innocently*