Converting 240VAC LEDs strings to 24VDC

damo1271

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If you’re like me and started out the hobby on a budget you probably ended up buying cheap 100-LED Chinese 240V LED strings from ebay or similar.
These strings typically have the 8 function control box and plug directly into the 240VAC (or 110VAC) mains socket.
The problems with using these strings are numerous.
Firstly the LEDs run on rectified 240V AC. This means that there is the potential for someone to be killed, or worse, if they come into contact with any bare wires.
These strings are generally used outdoors and of course 240V and water don’t mix. I cut off the 8 function control boxes and connected the strings to a rectified 240V output on my SSR, but if you use the control box, they are not waterproof and often very flimsy. You definitely don’t want to get water into there!
I had some LED strings that were probably 110V DC and the resistors ran quite hot. One or two strings actually smoked and I had to disconnect the string for fear of fire.
Finally there is a lot of power being wasted in those series resistors and this could be put to better use (eg more lights).

The attached PDF shows the method I use to convert 240V strings to 24V.
As with anything electrical you perform the processes described at your own risk. Furthermore the user should check the accuracy of any and all information before it is relied upon and I take no responsiblity for the accuracy of the information I provide or the way in which it is used.
 

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damo1271

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Oct 12, 2011
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Thank you.
I bought my strings from either Aliexpress or DHGate. I cant remember which it was now - probably the latter. They were about US$3.50 each for a lot of 200 inc delivery.
The supplier was very bad. She advertised free shipping and then had to charge me for shipping - which wasn't too unreasonable (about $40).
Also many strings had circuits that did not work and I had to fix them. There was no warranty as claimed in the listing. (surprise, surprise) She stopped selling them after my order.
Having said that I could not buy the individual LEDs for the price I paid, let alone build the strings, so overall I thought the deal was OK. $700 for 2Km of light strings giving 20,000 LEDs is pretty good I thought!
 

fasteddy

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great stuff, im sure it will help many. Thanks for the effort put into this and for sharing it with others.
 

Slite

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Dec 30, 2011
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Mölnbo, Sweden
I see that they advertise Icicle-strings very cheap as well on the "China-sites" can they be converted using the same general idea? By just checking what resistors they need to use instead?
 

damo1271

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I have never looked at the icicle strings to see how they are put together. In the few I just looked at, the controller looks to be the same as the regular strings and the LEDs seem to be in series. In theory they could be converted, but the question will be about how much work is required. You would have to trace the strings to find where to cut them and the cut might be 1/2 way down one of the icicles. Similarly, if you have to desolder a large number of LEDs to remove series resistors I would be inclined to either buy appropriate DC ones to start, or make them from scratch.
 

Cameron

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Dec 15, 2015
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Ivanhoe
I finally got around to converting my lights off this type to something useful. 16 strings converted to 24vdc, controlled by a 16 port relay and run by an Arduino Uno R3.

Only finished prior to Xmas, as soldering and shrink wrapping 48 resistors took longer then I thought. Will improve on the design for next year and program done more sequences.

Thanks to the OP damo1271 for giving me the original idea.

View: https://youtu.be/dlIU5EG-nd8
 
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