240v DC! led strip lights

[Oli]

A client asked me to fit some LED strip lights, 1m long, easy enough, they bought them, probably on Amazon, 3 pin plug with 6 inches of wire and then a very small plastic enclosure about the size of a switch, then another 6 inches of wire directly into the strip lighting. I needed to extend the wire so I cut between the little enclosure and the lights, I plugged it in and put my tester on it and was quite surprised to measure 240v DC! Anyone ever come across this before? I'm assuming the little box is a rectum-frier, but surely you can't have 240 DC swinging about the place. Wanted to know if anyone had seen it before and if anyone thinks it complies, I've already said I won't fit it and have supplied my own 12v stuff.

On a separate note it's the job that keeps giving, every single enclosure, fitting or CU I look at needs attention, the previous chap had used SWA glands for the SWA wire which was an improvement over the usual stuffing gland but then instead of terminating it just pulled the whole wire through and tightened it up by hand, class. Why do so many sparks find SWA so hard that they can't be bothered.

Hope your all doing ok

 

[ferg]

I thought most LED tape was 24v DC.

Are you sure there wasn't a decimal point in the wrong place.

 

[davesparks]

It's probably low quality electronics which float up to a 240V output when no load is applied.
Measure it again with the tape connected and you'll probably find its actually 12 or 24
[automerge]1588966686[/automerge]

I thought most LED tape was 24v DC.

Are you sure there wasn't a decimal point in the wrong place.

Most of it is 12V, 24V is available but usually sold as the high power version

 

[Oli]

I will double check again, as you have made me think maybe I've been silly. But I don't think so, I also didn't measure 240, I can't remember the exact reading but it was more like 230, usually the 24 volt stuff actually measures I little high.
[automerge]1588968004[/automerge]

It's probably low quality electronics which float up to a 240V output when no load is applied.
Measure it again with the tape connected and you'll probably find its actually 12 or 24

Really? Never heard of that. I would have to break them to test it that way as it's IP rated strip lighting, and it's technically the clients stuff.
[automerge]1588968065[/automerge]

I thought most LED tape was 24v DC.

Are you sure there wasn't a decimal point in the wrong place.

I've only ever fitted 12v volt stuff

 

[davesparks]

I
Really? Never heard of that. I would have to break them to test it that way as it's IP rated strip lighting, and it's technically the clients stuff.

You've managed to test the output of the power supply already so why would you have to break something to test it a second time?

Anyway, why did you cut the wire then plug it in? That seems like a bizarre thing to do anyway.

 

[ferg]

It's probably low quality electronics which float up to a 240V output when no load is applied.
Measure it again with the tape connected and you'll probably find its actually 12 or 24
[automerge]1588966686[/automerge]


Most of it is 12V, 24V is available but usually sold as the high power version

Fair enough. The stuff I use is 24v and the last tape I looked at as an alternative was also 24v so I given my sample size of two I may have erred slightly.

 

[pc1966]

Not personally but I guy I sometimes work with found such stupidly high voltages on what he thought was a low-voltage LED light system, could well be the same type! I don't remember the details but can check next time I speak to him.

 

[Oli]

You've managed to test the output of the power supply already so why would you have to break something to test it a second time?

Anyway, why did you cut the wire then plug it in? That seems like a bizarre thing to do anyway.

Re your first point, for some reason I thought I would have to test at the end of the LED strip, of course I can connect it and then test at my joint, didn't think of that.

re your second point, I wanted to know what voltage the small box in the line was putting out, it didn't look like a transformer, the whole thing was strange, so I tested it, no other way to test it but cut into the wire which I needed to do anyway to extend it, the rest of it was all coated in plastic as it's IP rated.

Anybody actually heard of 240DC being used anywhere or do you all just think I didn't measure it correctly.
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Iv'e found a product that looks very similar, not exactly the same but you can see the little box after the plug.
View: https://www.amazon.co.uk/XUNATA-Waterproof-120LEDs-Commercial-Shipping/dp/B07D59L23D/ref=sr_1_10?crid=259MAK1PPAJZX&dchild=1&keywords=1m+led+strip+outdoor&qid=1588975090&sprefix=1m+led+strip+out%2Caps%2C142&sr=8-10


claims to be 240AC which is clearly it's input voltage.

 

[davesparks]

Re your first point, for some reason I thought I would have to test at the end of the LED strip, of course I can connect it and then test at my joint, didn't think of that.

re your second point, I wanted to know what voltage the small box in the line was putting out, it didn't look like a transformer, the whole thing was strange, so I tested it, no other way to test it but cut into the wire which I needed to do anyway to extend it, the rest of it was all coated in plastic as it's IP rated.

Anybody actually heard of 240DC being used anywhere or do you all just think I didn't measure it correctly.
[automerge]1588975298[/automerge]
Iv'e found a product that looks very similar, not exactly the same but you can see the little box after the plug.
View: https://www.amazon.co.uk/XUNATA-Waterproof-120LEDs-Commercial-Shipping/dp/B07D59L23D/ref=sr_1_10?crid=259MAK1PPAJZX&dchild=1&keywords=1m+led+strip+outdoor&qid=1588975090&sprefix=1m+led+strip+out%2Caps%2C142&sr=8-10


claims to be 240AC which is clearly it's input voltage.

That stuff in the picture does work at mains voltage as far as I know.
It's far from an ideal setup in my opinion, but I don't think anything actually prevents it legally speaking.

That plastic blob probably does just house a rectifier so it gives out unsmothed DC.

 

[Lucien Nunes]

I suspect the box is simply a capacitive dropper and rectifier, the capacitor serving as a ballast that provides the correct reactance to drive the string with an approximately constant current. The whole LED current comes straight from the mains but the capacitor makes up the difference in voltage, obviously on the AC side of the rectifier. If the LED string voltage is low, the power factor will be very low also.

With the LEDs disconnected you would read 230V DC, as there is no significant current flowing to drop voltage across the capacitor. With the LEDs connected, you should find that the DC voltage across the string is whatever it needs to be (and that could be anything as it's approximately constant current) with one pole connected to the mains. Depending on whether the polarity is correct, it could be for example 20V DC hanging down from 230V AC. In any case, the LED string needs to be fully insulated to the same standard as a mains cable, as it poses the same shock risk.

 

[AJshep]

I've used it before. The 230v runs along the outside edge, its usually only cuttable every meter, and once cut it needs property sealing.
The insulation is thick too. Its probably the size of a 6mm T&E.
It does have its uses but if using it's best to by exactly what lengths you need and avoid joining it.

There is some Red 220v LED strip installed around the perimeter of a cinema screen local to me, for this type of application its ideal, but for general everyday stuff its probably best to stick with 12/24v stuff.

View: https://youtu.be/pxYCQTUZ_Dk

 

[Lucien Nunes]

I've just seen the pic which is different to what I expected, and would now say that there is no capacitor in the blob, it's just a rectifier, so the resistors on the LED strip itself are the only ballast.