LED Christmas Lights

Hi everyone,

I have some LED Christmas Lights here with those functions boxes that change the way the leds blink/fade. I would like to control the sections through an Arduino. So, I disassembled the function box and measured the voltage with a multimeter to find out how much energy I would have to use to turn them on.

Turns out that the output is about 190V DC (input is 220V AC). How can I get this voltage from another source and be able to control it?


The OUTPUT is 190VDC? For a LED string? Wow. Ok, well one choice there would be to use a relay, have the Arduino control the relay turning it on or off. Personally, I can't think of any other way, but someone here is bound to suggest something else.

Yeah, I also think it is very strange. It is a 100 led string (it seems to be divided in 2 sections). The problem is, I can't use the power from the function box as it changes the function from time to time, so I would need to get the power elsewhere (I could also change the function to steady lights each time I turn them on :P).

Ok, so you want a constant, clean power to the LED strings, and not the (programmatically) controlled power from the box. You’ll need to build yourself a regulator to take the 220VAC to 190VDC then … Actually, you should be able to pull power off of the regulator that’s in the control box, before it gets manipulated by whatever controller IC that’ss in it. I guess with two strings, 50 LEDs each, 190VDC comes out to 3.8VDC per LED. I guess they’re all in series then.

Can you run the lights on 110/120VAC? Normal house current?

@GoForSmoke the problem is that the here we have 220V AC :frowning: And even at 110AC, wouldn’t the LEDs just light up when the current is flowing in the right direction?

@KirAsh4 Yes! Thanks for the tip. I figured out where to get the power from the circuit board before it gets controlled by the IC. I guess I’ll have to use them to power the LEDs and find a transistor good enough to handle such high voltage (or maybe a relay, but I would prefer a transistor) to control the strings from the Arduino.

My guess is, that IC isn't just controlling the turning on/off of the voltage, but also current through the string. Can you get a part number off of it? Can you see resistors anywhere?

I was looking to see if the brightness fell.

Allelectronics sells, for example, LEDs with built-in resistors for 12V operation. That allows a 12V supply to run many with no worry about if one or more fail and no time spent soldering a whole pile of resistors. But they run about 50 cents US each unless you buy in real quantity.

Given that I can see that mass production would have the resistors built in and that does lead in interesting directions if the suckers can be gotten pre-wired relatively cheap, say on a string of tree lights.