View Full Version : 120V AC to ~3.5V DC ?

01-08-2009, 11:30 PM
I have been searching through the forums and haven't found an answer that I can follow enough to feel comfortable with so I'm asking here. I have some leds that operate 3.4-3.8V DC at 100mA and I want to use 3 of them together per channel with my grinch. I know I could try to build a DC SSR but I already have SSROZ and would rather make something to put between it and the leds. I have found some info about rectifiers and am not quite sure how I could get them to work at the voltage and amperage I would need. Has anyone done this or know a fairly easy/cheap way to make it work? Thanks

01-09-2009, 03:51 PM
You're going to need a transformer of some sort (wall wart would probably work), a full-wave bridge rectifier, a voltage regulator (depending upon the amount of voltage coming out of the transformer/ww) and a resistor or two.

I have some circuits drawn up that are similar; PM me and I'll adapt one for you.


01-12-2009, 02:49 PM
For anyone reading this thread with more interest:

We have discussed using a wall wart for each channel. Using the full wave rectifier would guarantee that it was DC and would not affect anything if it was already DC. To find a resistor to use with the leds, google "led series resistor" and there are calculators to find what resistor is needed.

As of right now, I'm looking for 12v wall warts that I will put 3 leds and a resistor in series, as apparently leds need a resistor since they don't necessarily drop voltage linearly as incandescents do.:confused:

01-13-2009, 12:58 AM
Master Gracey...

I believe that the series resistor is used to limit the amount of current flowing to the LED's, not to drop the voltage. If the LED gets too much current, they'll burn out fairly quickly. So even if you the get voltage where you need it, you'll still want to use a resistor in series with it.