Post by vonFrenchie on Jul 9, 2006 17:46:24 GMT -5
Im building a pedal that calls for a 9v battery. I also have a 9v 300mA AC adapter from radio shack that I would like to use. How could I wire a switch that would allow me to choose between the battery or adapter? Should I even use a switch?
Post by vonFrenchie on Jul 9, 2006 21:25:35 GMT -5
Well the thing is.... Im building the pedal. Its not designed to have two power supplies. Its designed to be powered by a battery. I wouldnt know what diodes to use and where. Also I understand the power usage thing. I have some 9 volt batteries that have a charge of 8.5 volts. The thing is I would prefer, PREFER, to have it from supply A or supply B. I dont want the pedal to chose.... I want to. Unless it would be easier with the diode thing.
If I were doing this, and the load was less than 50 mA, I'd use the glass switching diodes such as 1N4148 or 1N914 since they have substantially less reverse leakage current than the garden variety of 1N400X power diodes.
Diode reverse leakage current will result in inadvertent charging of the battery when powered by the adapter.
Most adapter jacks have a switching contact built in. The battery can go thru the jack switching contact, and is disconnected when the adapter is plugged in.