Help Me H4x0r My Xmas Lights?December 21, 2011 9:07 PM   Subscribe

I bought a few strands of cheap LED Xmas lights this year. They include a circuit box with several settings to make the lights flash in different patterns. The circuit box resets itself (to a new annoying setting) each time the lights are unplugged or when it shorts out in the rain, and I also suspect the box is the product's "built-in expectancy" (since otherwise LEDs might last too long to be profitable. Can I bypass the box?

Each string of lights 120 lights is made up of 2 connected strands, with each lamp in the first strand connected to three wires and each lamp in the second connected to two wires; 120V 60Hz 0.6A, "Indoor Outdoor Use".

Thanks!
posted by Shane to Home & Garden (8 answers total) 1 user marked this as a favorite

Response by poster: Oops, previewing took out my linky (?)
posted by Shane at 9:13 PM on December 21, 2011

I don't have an answer for you, but you might try asking on the forums at doityourselfchristmas.com.
posted by eruonna at 9:49 PM on December 21, 2011

Response by poster: Thanks, eruonna. I'll check it out. It looks a bit technical for me, though -- I'm basically just wondering if I can cut the cords on either side of the box and splice them back together and, if so, which wires to which.
posted by Shane at 10:41 PM on December 21, 2011

LEDs are low-voltage devices --- a green photon has an energy of about 2 electron-volts, so the drop across a green LED is about two volts (the rest of the voltage drop is usually across a series resistor). Probably your box converts the 120V alternating current from your wall into 5V or 10V direct current, and it's probably pulsed.

If you know how to use a voltmeter, you can check that the input to the box is 120 VAC (from your wall) and whether its output is large AC or small DC. If you put 120 VAC into a 10 VDC system, you'll be dissipating about one hundred times the designed-for power and you will probably let the smoke out.

If you don't know how to use a voltmeter, don't bypass your box.
posted by fantabulous timewaster at 11:47 PM on December 21, 2011 [2 favorites]

One other comment: lights that say Indoor Use Only probably should not be used outside where they can short in the rain. This can be anything from mildly non-ideal (if your housecis wired correctly and all outlets in question have GFI) to incredibly dangerous with (reasonably common) wiring errors.
posted by JMOZ at 4:33 AM on December 22, 2011

The short answer is, no, you can't just cut out that box.

There's nothing inside that box that says "planned obsolescence" to me; it looks like a single-sided circuit board with some components that are probably of the same quality as everything else in the string. It's not like there's a timer in there set to shut the thing down in 18 months. (Though it's probably less waterproof now that it's been opened.)

How do you set the patterns? What are the patterns? Where does power from the wall come in? I'm having a hard time seeing how those components are going to make anything interesting happen (unless there's an IC on the other side of that board we can't see). The part on the left could be a bridge rectifier (4 diodes, big-ish capacitor), but I'm not sure why -- lots of LED Christmas lights just run a bunch of LEDs (and a little resistor) in series directly to the power mains (110VAC is actually a ~150V sine wave, so you can run something like 50 red LEDs in series and have them "flicker" (invisibly) at 60Hz.
posted by range at 6:24 AM on December 22, 2011

Before we can give you a good answer, we have to figure out what you've got there. What's the brand and model number?
posted by exphysicist345 at 8:29 AM on December 22, 2011

Response by poster: Hey, thanks for the answers.

I'm having a hard time seeing how those components are going to make anything interesting happen (unless there's an IC on the other side of that board we can't see).

range, There must be an IC, because they have settings (based upon clicking the same switch, some kind of little toggle under a small rubber cap) to strobe at different rates, fade out and back in, flicker in diff patterns, etc. etc., maybe 6 - 8 diff settings in all, all of which (except just staying on and doing nothing) I find annoying.

exphysicist345, they are "TCP" brand, sold at Marc's, probably from China. Somehow I doubt that tells you much, heh.

As far as planned obsolescence and the box no longer being waterproof, based upon the little stringy rubber seal between the cover and the box, I don't think the boxes ever were very waterproof, and at least two strands are already acting wonky, resetting themselves to different patterns and sometimes just a half-set of lights going out altogether. I still think that, if LEDs are ever to replace traditional Xmas lights, they'll build in a planned obsolescence, and I think that cheap little box and circuit board do the trick here. No company makes anything to last forever unless it's a really damn high-end item.

fantabulous, I'll borrow my uncle's ancient (but working) voltmeter as usual. JMOZ, good point -- I think I'll start taping the connections between my extension cords, as we get so much winter rain and moisture here in Ohio that it's rare I don't have at least one set of lights per season short out.
posted by Shane at 10:33 AM on December 22, 2011

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