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Unusually safe Chinese eBay lights (Patreon)

Published:
2023-11-18 16:11:41
Imported:
2023-11

Content

I was almost hoping this power supply was going to be terrible inside, but it actually seems to be made to local safety standards.

It took a while to reverse engineer the primary side circuitry, because the chip isn't one I recognise and I didn't get any clues from the number on the IC.  Even a search for a cloned original didn't find any with a matching pinout.

It does have some hackability for reducing the current delivered to the LEDs, and unlike many high-street versions here, it actually has the memory chip for storing the last setting.

It could be viable to buy a string of these just for the power supply if you have a matching two wire 30V set that defaults to flashing effects or has a failed power supply.

https://www.youtube.com/watch?v=ajnw_b8FBRU

Files

Safe eBay fairy lights? (with schematic)

Given eBay's shocking reputation for facilitating the import and sale of extremely dangerous goods, it's a pleasant surprise to find an import that seems to be compliant with safety standards. Note that due to the unregulated nature of eBay there is no guarantee that an identical looking listing would supply the same product. The fact this unit has memory for the last setting means it might be a useful replacement for existing favourite strings of lights that also use the two wire 31V system. Quite a tricky one to reverse engineer due to the use of an unusual switcher chip configuration on the primary side. The secondary side is very minimalist due to the use of an ASIC (Application Specific Integrated Circuit) that deals with all the lighting sequences, driving the LEDs with an integrated H-bridge and also storing the current selection to non volatile memory. This unit puts out around 30V of alternating polarity. The LED string is wired as ten parallel circuits of thirty LEDs , all wired in a series string to give a combined voltage of about 30V. Alternate LEDs in each parallel section are wired with opposite polarity to allow simple 2-channel flashing sequences. Static mode is actually rapid switching between the two channels. I swapped out the sense resistor to see how it affected the power. 2.67 ohms (original) total unit power 4.5W 3.3 ohms total unit power 3.8W 5.1 ohms total unit power 2.2W but unstable with notable intermittent shimmer. I would like to have tested it with 3.9 ohm and 4.7 ohm resistors, but didn't have any in that surface mount package. I would guess that 3.9 ohm would be the highest value for stability. If you enjoy these videos you can help support the channel with a dollar for coffee, cookies and random gadgets for disassembly at:- https://www.bigclive.com/coffee.htm This also keeps the channel independent of YouTube's algorithm quirks, allowing it to be a bit more dangerous and naughty. #ElectronicsCreators

Comments

Seán Byrne

I think this is the first electronics item I seen you feature that has the new UK CA logo, but not a CE logo.

Dave Frederick

Very cool and thank you Big Clive. Sometimes it's nice when you get stuff that's compliant and decent so as to offer a contrast to the spicy dangerous stuff. The cutout around the 10 ohm resister is interesting. My first thought was for making it fit in more of a streamline fashion but yea, the failure of such won't make a metallic dead short track between the live and neutral. Nice. Thanks for sharing.

Anonymous

There's a discussion of the EU (rather than UK) version of the power supply at https://github.com/arendst/Tasmota/discussions/14016. Tasmota is open-source software for ESP devices, so this thing might have hidden tricks up its sleeve.