Re: 12 volts to 5 volts and Back again..

[jackbrad]

The 7805 should be fine to power the micro-controller. The micro-controller must have darlington transistors with base resistors on its output to drive the 12V/2A relay coils.

So if I go grab a 7805a from Radio Shack and hook it up right  :) That should take care of the 12v > 5v convertion.

Then for added protection

"To protect the regulator against the nasty high voltage spikes generated in the car's ignition system, connect a 16V to 33V 1W zener diode across the power supply to the regulator."

That would mean just placing the diode between the postive voltage source and the input terminal of the 7805 regulator... correct?

I have also heard that I shoudl use a 220 mf capacitor between the output of the regulator going to the and the micro controller ground to balance any spikes in the output voltage.

Does that sound like I have all that correct?

Then from the 5v pins to engage the 12 v relays, I need to configure:

"darlington transistors with base resistors on its output to drive the 12V/2A relay coils."

Any paticular models? for these transistors?
I knwo that you can by a IC that has the darlinton transistor built in but, I am not sure exactly what is a good model