Some VERY interesting LED modules

I am posting this for two good reasons:

1. The technology is innovative [and had until recently gone un-noticed by me]
2. There is a UK ebay seller offering them remarkably cheaply

For background … have a look at this: **LINK**

https://www.electronicproducts.com/how-gan-on-si-high-power-led-chip-technology-is-changing-luminaire-design/

Now hop over to RS components; check the price and download the Plessey datasheet: **LINK**

https://uk.rs-online.com/web/p/led-arrays/1696963

At first glance, they look rather tacky … but that’s just the aluminised plastic … the clever optical design is within the individual LEDs.

I have already purchased the last few of the narrow angle, low colour-temperature, modules from ebay [for my photographic lighting] but the seller is still listing some of the other variants. … Anyone considering new workplace lighting might grab a bargain.

Note: The voltage requirements are unusual, but that’s no great problem.

MichaelG.

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https://www.ebay.co.uk/itm/143502772640

Edited By Michael Gilligan on 03/01/2023 10:16:02

Interesting, but what a strange voltage! I have a small array of solar panels, and 12volt battery storage. At present running the door bell, and spot lights using Mr16 Led Bulbs 12v AC/DC (5W Equivalent to 40W Halogen),4000K Natural White Spotlight,Non-dimmable from Amazon, which cost just under £12 for 4. Using 'Buck converrers' for lower voltage items. Seem to be working fine at the moment. At least if there are power cuts this winter we will have light!

Hello MichaelG. I've got two of those lights but have seen a proper electrical supply connector, can you point me in the right direction please. John

The ‘connector’ is internal, John … it’s just a matter of poking bare wires into the two little holes.

[there are two more holes to release the spring clips]

Doesn’t feel comfortable to an Engineer … but there is surprisingly clever engineering involved.

MichaelG.

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Note: The Plessey data-sheet specifies solid wire 0.14 - 0.34 mm 

a.k.a.  AWG 26 - 22 “sol”

Which sounds like common-or-garden hook-up wire to me.

Edited By Michael Gilligan on 07/01/2023 18:29:31

As with all LEDs these require a constant current supply not a voltage. These require 0.7 Amps for the rated output. The voltage quoted is the typical voltage measured across the LED module at the specified current. As they seem to have 42 LEDs it is probably 3 parallel strings of 14 LEDs in series so 3.2V per LED.
At the typical forward voltage of 44V at 0.7A if you had a 50V supply you could put a 8.6 Ohm resistor in seres to get the 0.7A (50-44)/0.7. Note that this does not provide a very constant current. If the LED voltage or supply voltage changes by 1V (0.5%) the current will change by 0.116 (16%). So these really need a proper constant current supply. While people do run LEDs voltage sources it is bad practice and shortens the life of the LED.

Nice units though if you need something flat.

Robert G8RPI.

Edited By Robert Atkinson 2 on 07/01/2023 20:18:12

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Downloadable from RS, and highly recommended

MichaelG.

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Never one to turn down a bargain I snapped up four of the 60 degree 4000K for a paltry £8.44 - £12+ apiece at RS!

But ... how do you propose to power them Michael, and what is your plan for heatsinking? I have a bench top power supply which will supply the voltage and limit current for experiments, but something more permanent would be good. At 43ish volts and 700mA they're about 30W so will get hot.

Tangentially, I lit on on an RS press release when looking for datasheets. I was glad to hear from RS COO Mike England that:

“We see continued consolidation in the customers and competitors landscape and we are confident we can grow organically and inorganically”

Can anyone translate?

Robin

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Good questions, Robin

For my intended purpose [which broadly categorises as ‘photographic lighting’] the heatsinking will surely evolve [ risk of drifting into Mike England’s mind-set duly noted ] … I have some substantial passive heatsinks ‘in stock’ and will be taking temperature measurements in due course. The alternative, but less attractive, approach being to use fan-cooled heatsinks salvaged from desk-top PCs.

The casual comment about supply voltage rests on the fact that I have a “yellow transformer” available: The 110 volts from these is, of course 55-0-55 … which seems like a good place to start.

My own major interest in these units is the devious optics … beam-forming which typically requires bulky lenses or mirrors is consolidated into the landscape [thanks for the words, Mr England] of a thin disc.

MichaelG.

Edited By Michael Gilligan on 08/01/2023 08:10:12

To run one of these modules off 55V (half a 110V Tool transformer) you would require a bridge rectifier, 1000uF 100V electrolytic (Not critical as long as voltage is 100V or higher) and a 47 Ohm resistor. The resistor will be dissipating 23 W so needs to be suitably rated I would uses a 50W 47R metal clad e.g WH50-47. Note that these need a heatsink, even the 50W one. The 25W version might seem OK but at 23W it will need a 544 square centimeter sheet of 1mm aluminium as a heatsink and still get pretty hot. See resistor datasheet for hearsink requirements. Other vendors (RS etc) available.

https://uk.farnell.com/tt-electronics-welwyn/wh50-47rji/resistor-50w-5-47r/dp/9508422?

https://www.ttelectronics.com/TTElectronics/media/ProductFiles/Datasheet/WH.pdf

Robert G8RPI.

Edited By Robert Atkinson 2 on 08/01/2023 09:23:19

Thanks, Robert … Yes, we are already on the same page

MichaelG.

I just ordered a 25 degree one with a specialist application in mind.

Robert G8RPI.

On the Power Supply issue …. I have not yet found any proper documentation, but there is a very useful-looking module listed on ebay by various Sellers:

DC-DC Converter Constant Current Power supply 250W 10A Step up Boost LED Driver

If it performs as described, it might do nicely.

MichaelG.

Looks like those would work to operate from a 12V supply. Shame the technical dats is soo poor.

This would do for mains operation

www.ebay.co.uk/itm/274690953765?

Robert G8RPI

This appears to be the next model up of that power module:

**LINK**

https://youtu.be/xSI9k5BK-jU

with description.

MichaelG.

I am not so sure one of those would work with these modules. Looking at the Plessey datasheet the module will not start conducting until it sees about 40 Volts.

When LED's were first introduced that were virtually all a single LED junction with two connections and were always 'current driven' (often using just a resistor). Nowadays the term LED seems to cover everything from one junction to complex series parallel arrangements (sometimes with built in control). The ebay seller of the modules states they are 'Rated at 46.5 Volts' but that does not mean they are to be operated off a 46.5 volts supply. I suspect they would expire immediately on connection!

My take on these modules is that they need a constant current supply with an open circuit voltage above 40V. The DC:DC CC ebay module Michael suggested looks ideal as it has a max output of 48.

Ian P

Although I have already referenced it [somewhat obliquely] here is a direct link to the Plessey data-sheet:

**LINK** https://docs.rs-online.com/3995/0900766b8161ece2.pdf

MichaelG.

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If all goes well, I might dissect one of the LED modules this evening

pro bono publico

MichaelG.

Hi Ian, Are you refering to the DC-DC converter MichaelG mentioned or the mains to DC one I linked too? The units I linked to are 240V AC mains in and the CL700 model has a 700 mA output up to 48V and specifically says up to 4 x 14 LED strings.

"700mA model can be used to drive 4-14 x 3W LEDs, or 1 x 20W LED (48V max)

The Plessey modules have three 14 LED strings (42 total) and 44V drop. We must assume that Plessey have adequately addressed the sharing of current between the 3 parallel strings. The CL700-240 appears to be a perfect match.

Robert G8RPI.

Robert, it was the ebay mains units I looked at but TBH only looked at the 1A version that had a 33V output. The 700mA would be fine as you say

On the subject of discrete LED's when I first started using them putting them in parallel was not something we ever thought about doing as the differences in forward voltage of each junction would mean they probably would each have different brightness and a high failure rate.

Ian P

As promised ... a few seconds prising with the trusty Swiss Army Knife 'bottle opener cum screwdriver" revealed this:

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Apologies for the focus ... I just popped it on the flat-bed scanner

[ I might photograph it properly tomorrow ]

Hopefully the tracks are visible.

That 'board' is actually on the surface of the steel anodised aluminium heatsink, and the LED chips are tiny

The clever optics is all in the cover

MichaelG.

Edited By Michael Gilligan on 08/01/2023 20:09:04

[ UPDATE ]

This, snapped on the iPad, will probably suffice:

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MichaelG.