On Tue, 1 Apr 2003, Mark Belanger wrote: > I have a small battery charger for a portable electronic device that I'm > trying to wire into the car power system. Unfortunately, it takes 9V. > I know I can run it off the 12V if I want to give the battery a short > life, but how can I bring down the 12V to 9V? Is it as simple as > soldering one of those cheap 3-pin voltage regulators? If the current is fairly low you can do this. Most 3-terminal regulators are good for a few hundred milliamps with no heat sink, or up to 1.5 amps with one. You probably won't find a fixed 9V regulator, but if you buy an LM317 variable voltage regulator you can use a fixed resistor network to set it at 9V. Or you could try using a 7805 fixed 5V regulator and lifting the ground pin 4 volts above actual ground with a couple of red LEDs in series. As a side benefit the LEDs can serve as a power light.
David Brodbeck, N8SRE '82 Diesel Westfalia '94 Honda Civic Si |
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