Printable View
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.
..ooops...yeah, so I realized I screwed up the transition from paper to Eagle the first time...this is what I did.
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:
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.
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
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*
