LED lighting panels

[alanambrose]

Hi,

I installed 4 off 600x600mm LED lighting panels in my workshop about a year ago and they've been great and very bright. But .... two have failed already. So does anyone have a source for reliable LED panels?

TIA, Alan

[Colin Barron]

Is it the panels or the power supplies? I have a couple of led work lamps that stopped working and it was the power supplies.

[Voicecoil]

I've had similar experiences - unless it's a matter of poor heatsinking and the LED chips getting too hot it seems to be the PSU's that fail most often. They usually have the voltage and current ratings written on them, generally easy to source e.g. on the Bay of fleas.

[alanambrose]

Yeah I thought it was the power supply and ordered a replacement. But actually it's the panel that has failed. I can describe the design and failure in more detail (I'm an electronics guy), but ultimately the panel and PSU combinations I have (supplied as pairs) clearly have a design problem. So I have resigned myself to replacing them. That's why I'm looking for recommendations for reliable ones. These ones I have come from the eBay seller 'strictlylamps'. Yeah, I can probably get replacements from them, but I would like to stop messing about with the panels and actually use my workshop for its intended purpose :)

So, does anyone have panels that have been good for more than a year?

Alan

[alanambrose]

Well for anyone following along in future, I took one panel apart:

The leds are arranged in two strings, one on each side, each string 7 off x 14 parallel LEDs. Each string of 14 is in one contiguous section. The forward voltage of the LEDs is ~2.5V, and the driver says 1.15A (I didn't actually measure it). So actually the voltage drop will be ~14x2.5V = 35V, the power drawn by each LED about 2.5 * 1.15 / 14 = 205mW. There are 14x14=196 LEDs total so 196x0.205 = 40.25 watts total. That's all assuming the power supply is delivering what it claims on the can.

A bunch of the individual LEDs had failed - about 10 on one side and 20 on the other. When 14 LEDs in a segment fail, then the panel doesn't light at all.

I suspect the failure mode is either low quality or over-driven LEDs. Once one fails in a 14-segment string, then the remaining 13 will split the increased current/power. Then they probably pop one by one, until all in a segment are bust and the panel goes dark. That could be the cause of the 1 Hz flashing death rattle. I didn't have the time to muck about further with this, but my current theory is that low temperature spell recently caused some drivers to deliver too much current. I could be wrong.

I've just ordered replacement branded Philips panels from CP Lighting item # 911401899780 at £30 a go - about 40% more than the previous supplier. Hopefully Philips test them better, time will tell.

[Doddy]

14 parallel LEDs? without independent current limiting resistors?, that's a crap design - the drive circuit will - as you say - be designed to drive the power of each LED, but any variance (and they'll be plenty) in the characteristics (forward-volt drop) will see that particular LED consume more power and fail sooner - and, as identified - that results in a cascade of subsequent LED failures.

Designed to fail.

[Muzzer]

I don't have panels but I've got 6 of the 6' long LED battens by LAP from Screwfix in my workshop. I've been using them for 4 years now without any problems. They have a 3 year manufacturer's warranty, so you should have some confidence in them. https://www.screwfix.com/p/lap-twin-6ft-led-batten-60w-6100lm/2047g?_requestid=70189

There is a myth in the UK that products go out of warranty after 12 months. Not much point claiming 30,000h life (3.5 years) if you only give a 12 month warranty. However, if you buy from ebay or Aliexpress, you may struggle to get redress anyway.

[Kitwn]

14 parallel LEDs? without independent current limiting resistors?, that's a crap design - the drive circuit will - as you say - be designed to drive the power of each LED, but any variance (and they'll be plenty) in the characteristics (forward-volt drop) will see that particular LED consume more power and fail sooner - and, as identified - that results in a cascade of subsequent LED failures.

Designed to fail.

And somebody will have been paid to design that!

In practice LEDs are best supplied with a constant current supply rather than constant voltage as the forward voltage of the devices is very temperature dependant. I think most commercial units have a simple chopped AC drive circuit which is unidirectional but pulsed. A propper constant current DC supply will give a stable light output and greater reliability. You can also dim them very easily over a wide range. I designed and made a set of hight stability, dimmable LED stage lights for my former animation studio a few years back. The drive circuit isn't expensive to build and is fed from a standard Chinese switch-mode PSU. I can probably find (or redraw) the circuit if anyone is interested.

[alanambrose]

I thought I would report back:

I installed the Philips panels as replacements - that took 1/2 a day. They're thicker and stiffer than the originals, with the LEDs distributed over the panel rather than just down the sides. They're a bit less blue / more yellow in a side-by-side comparison, but not objectionably so. A bit thicker - about 35mm vs. 10mm - which was helpful in my application as the other ones flexed a bit when they got hot which made the light less uniform. The Philips power supplies have an annoying smart-arse sprung connector which is best connected on the bench rather than in the dark / above your head / up a ladder. They look better quality than the others, time will tell.

Alan

[A_Camera]

And somebody will have been paid to design that!


...probably not a lot...

Also, some times management's decision can not be overruled by an engineer's recommendation. Especially not in those cheap labour countries. So maybe it's not the designer's fault but the management taking stupid decisions without enough knowledge about the subject.

[cropwell]

I would just like to add my little bit :- If you buy from ebay, most sellers are acting as second source. i.e you don't have the redress of warranty in the case of premature failure of goods. Some sellers may do the honourable thing, but they have no compunction in law. Amazon offers better protection, but the prices are higher. For things like lighting panels, I would stick to a reliable source like CPC or RS.

[Kitwn]

...probably not a lot...

Also, some times management's decision can not be overruled by an engineer's recommendation. Especially not in those cheap labour countries. So maybe it's not the designer's fault but the management taking stupid decisions without enough knowledge about the subject.

Putt's Law comes to mind here...

"Technology is dominated by two types of people: those who understand what they do not manage and those who manage what they do not understand."