Running 36v Xmas lights on 24v transformer

December 8, 2013 1:47 AM

We've lost the original transformer for our Christmas lights, will there be any problems with running on a differently rated transformer? Lights are LEDs and both lights and transformer are rated at 1 amp.
posted by Kiwi to Technology (7 answers total)

It's a bit hard to say - it really depends on how the lights are controlled - but lower voltage shouldn't damage things. They may not work though. If it were me I would check it out, but be prepared to turn it off again quickly. Better off getting another 36V transformer though.
posted by mewsic at 2:57 AM on December 8, 2013

LEDs require a particular voltage to turn on properly. If the voltage is too low, the LEDs will either run dim or not turn on at all. There should not be any safety issue with trying the 24V supply, but it may simply not work, or provide enough light.
posted by Behemoth at 4:45 AM on December 8, 2013

They'll simply be uselessly dim. No damage is going to happen.

A lot of stores are having ridiculous sales on the new LED lights that don't need transformers however(which are already cheap anyways). Like, $2.99 a 100 strand. I don't know if i'd even bother with replacing the transformer unless they were really really cool lights. A lot of early-ish LED christmas lights used weird voltages like that. The new ones are brighter and simpler to deal with.
posted by emptythought at 5:00 AM on December 8, 2013 [1 favorite]

I think the poster is in the UK. Just saw a note from a friend of mine complaining how Christmas lights in the UK were going for ~$20 USD. The $2.99 price might not be valid over there.
posted by kellyblah at 8:09 AM on December 8, 2013

Think of voltage as a hamster treadmill. You need 36 hamsters to run the treadmill, but you only have 24. Squashing 36 hamsters onto a 24-hamster treadmill will make it go too fast and be overloaded. 24 hamsters on a 36-hamster treadmill likely won't be able to move it.

What will likely happen is that the LEDs won't come on at all. Incandescent bulbs will light up but just be dim because the filament isn't getting hot enough to give out light. LEDs (generally) need a specific voltage to do their thing.

Personally, I wouldn't risk it. While it's likely to be safe, it's not guaranteed. Maplin (if you're in the UK as suggested) might do a transformer that would work for you.
posted by Solomon at 9:21 AM on December 8, 2013

Typically, LED strings like this have the diodes wired in series to equalize the voltage drop along the string and supply each diode with the proper voltage (~2V depending on color). Because your string requires an odd voltage, this tells me that there is some other circuity controlling the voltage to each diode, and this circuity may very well require 36V to operate.

Having said that, I'd give it a try if I were you - you won't harm anything by supplying the string a lower voltage, but expect it to either not light up at all, or to only have a portion of the string light up.

But, as others have mentioned, just buy a new string for $2.99 that can be plugged in to 110V AC directly.
posted by mrrisotto at 10:46 AM on December 8, 2013

Response by poster: Thanks all, will give it a try and see.
posted by Kiwi at 1:22 PM on December 8, 2013