Hi,

I would like to add a 9v power adapter to my circuit so that at anytime the wall wart is plugged in the 9v battery is cut out of the circuit. I know this is a really common practice but I can't find any examples except for using an LM2601. Can someone help me with this circuit? Thank you.

WJB

 

They make barrel connectors that do that mechanically.

http://www.radioshack.com/product/i...ce=CAT&znt_medium=RSCOM&znt_content=CT2032231

 

I made an LED vu meter that has a microphone. It is usually powered from a 9VDC wall wart but it also has a 9V (actually 8.4V) rechargeable battery for portable use. The battery is continually trickle-charged by the wall-wart.

If your circuit uses a non-rechargeable battery then you can use a common jack with a built-in switch. The switch allows the battery to power your circuit when the adapter is not plugged into it. When it is plugged in then the switch disconnects the battery and the circuit is powered from the adapter.

 

Assuming that your power adapter has positive on the center pin, here is the way it is wired in order to disconnect the battery when the adaptor plug is inserted into the jack.