Richard said:
Dear all
I want to design a power supply for a low power rig with protection for
reverse and overvoltage. The requirement would be about 1A at 12-14V.
What is the best way of achieving this? I guess a diode would give
reverse voltage protection but the 0.6V drop is a problem.
Richard
If the voltage drop from a diode is a problem, perhaps consider using a
larger (voltage) transformer with a readily available 12-v voltage
regulator like a 7812 chip. The regulator chip comes in several
varieties, and I'm not sure, but I think the 7812 that radio slap sells
can handle an amp an a half. This will keep the voltage at 12v pretty
steady, but you'll need a 15-volts-when-loaded transformer to feed it
properly.
They also have other voltage regulator modules that would provide a high
enough voltage that a few .6 volt drops would be acceptible. May not look
very pretty, but once it's in the case, nobody will know.
You can also do what I just did... I thought I fried my 7812 regulator,
and I found that it hadn't been regulating at all (because the supply
voltage was at 12v when under load, not enough for the chip to regulate),
so in my soldering, I got it backward once, and it got really hot. I went
and bought an LM317 from Radio Stank and have been using it. Now I can
vary my voltage from my new 26 volt transformer from 1.2 up to 35v (35
under no load). Only bad thing here is my box is too small to fit the
larger transformer and 3-inch-square heatsink I need ;-/ But with a large
enough box, it should do quite nicely.
By the way, at the RS, the 7812 regulator is $1.49, and the LM317T is
$1.99. Both are TO-220 cases.
Just my thoughts...