'Soft' On/Off Power Switch

[Corey]

Hi,

Try using an LM2941 linear regulator. They need to be configured, but I've attached a VB program that does all of the calculating for you. You should still take a look at the datasheet though.

They are great little linear regualtors and can also be used as a 1 amp switch.

They have a control pin that must be tied low for the unit to work.

I designed a circuit that tapped a signal off of the RS232 TX line from my PC. The RS232 line drove a transistor (2N3904) which charged a capacitor that, when it reached a certain voltage, drove another transistor that brought the regulator's control pin low. Then, when the regulator turned on, the PIC would start up and would drive one of it's pins high. This pin would take over from the RS232 signal and would hold the PIC on.

You could then turn off the PIC and the entire circuit with a simple command to make that same pin low.

Super easy!

Good luck.