Quote: Originally Posted by shotgunefx
autospeed.com had a nice article on replacing the lilliput ps with a 7812 and a zener. I'll see if I can find it.
UPDATE
I've attached the 7812 based circuit.
First off, I am by no means an electrical expert. Hell, I just know enough to be dangerous.
Use at your own risk. You should test the completed circuit with a multimeter before hooking up anything important.
Having said that, I've built this circuit (minus the zener) for other projects and it's always worked fine. Your mileage may vary
Outside of the Zener, everything should be available at Radio Shack.
1) 16v zener diode
1) 7812 regulator
1) 10 uf cap
1) 100 uf cap
1) 5W 1 Ohm resistor
1) Heat sink, bigger is better
Some notes:
1. A regular 7812 only allows up to 1A output. For more output, look for a 78S12, that one is able to handle 2A.
2. Heatsink IS requires, bigger = better, ok, but in my case, an old CPU fan does the job perfectly.
3. The capacitor on the input is almost useless, since its directly on the battery. To give it a better use I suggest adding a diode before it, so it will only buffer the 7812, and not your lights/hu/and so on. However, adding a diode causes a decrease of the voltage with about 0.7V.
More important: For
good regulation the 7812 requires an input voltage of about 2-3V
above the desired output voltage. So its very doubtfull if this will work in the car, since the car voltage IS 12v, and, during drive, about 14V...
Better use a low-drop regulator, since they require less input.
I suggest using 12V from the pc powersupply, or, in my case (i am using an old laptop) connecting the 7812 to the 16-19V output (which my laptop requires)
Or a good switching regulator, saves the heating troubles also
