I bought a bunch of these 3mm led lights in various colors for projects I'm thinking about. Problem is they only light with 5 to 12vac current. Did I miss something in the details, or what? Can't get them to light hooked to buck converter with 4-12vdc output. As We all know, off shore prices are cheap so certainly not out any money, but kinda wanted dc lighting. Any help out there? Or, just buy a 12vac wall wart and be done with it. Thx for any assistance. TW
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Should be a resistor under the heat shrink tubing somewhere. I can see the bulge in your second picture. Look and see if one led of the led is thicker than the other. You can use a exacto knife and slit the heat shrink open and take out the resistor. The led itself should light up around 2 -3 volts. If not reverse the led wires on your power source and try again.
They should light on DC if they light on AC, they are polarity sensitive. Like Steve says, there's a resistor under the heatshrink, at the red arrow. I'll guess 470 ohms. 
Yup, I knew about the resistor. But, didn't(wouldn't have) think of reversing polarity. Isn't that illegal or something? 
They sure do work though, at 4.6vdc. Thx cause I never would have tried that.
The red wire is positive, you can tell that by the looking at the clear LED. The positive side (anode) is the smaller electrode.
Ok, I trusted red was positive, and your diagram helps(some). But why does ac light work + to + but dc light works - to +?
AC is "alternating" current, so it changes polarity 60 times a second. No matter how you connect, you'll get the correct polarity to light the LED half of the time. It will light the LED no matter which polarity you pick as AC really doesn't have "polarity".
TedW posted:Ok, I trusted red was positive, and your diagram helps(some). But why does ac light work + to + but dc light works - to +?
I can't quite make out the lettering on your board, but is there a chance you hooked the minus or black wire to the positive or OUT+ of the converter module?
Nah! 
Not a chance. But let's just check to prove Ol' Stan wrong. Bingo! 
What the h..l! Ten seconds later, wires switched all good(maybe). Course I was just testing you all. 
Knew it all the time. TW
EDIT: It's a wonder I don't blow myself up...
TedW posted:Nah!
EDIT: It's a wonder I don't blow myself up...
Been there, done that--and worse
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