4 Apr 2016

50W red LEDs cheap on eBay

Bernie G4HJW recently posted to the UK Nanowave Yahoo about some powerful red LEDs that he bought from China for just £2.80. A couple of these are more powerful than the 10mm LEDs that I used in non line of night tests (when I was fitter) but even without any lenses!  It would seem these would be ideal for optical tests. 50W is a lot of power. This was Bernie's post. I trust he won't mind me sharing it with you all:

"Morning all - This might be of general interest:

I recently bought a couple of 50W red LEDs from China, which I thought I might use in a wide-angle initial set-up lantern for portable use. They were very cheap (£2.80), so I also expected there would be dead segments, which there were, but there was a bigger surprise waiting to show itself.

During this weeks UK uwave group net, Martyn G3UKV asked me how wide the spectrum was, so out came my trusty secondary school Spectroscope. Instead of the expected relatively narrow response, there was noticeable output right through to yellow plus a weakish narrow line at the violet end. This should have been an obvious clue, of course, but it was only later when I was telling Stuart G8CYW (sorry about all the name dropping..) that he suggested  that the LEDs might be fluorescent driven devices, just like the white lighting LEDs all seem to be these days. He was correct, as the following picture shows:


Note that in pealing back some of the fluorescent gell, all but one of the individual 1W UV leds have been destroyed. Not obvious from the picture is that these LEDs are embedded in an initial clear silicon rubber prior to the red fluorescent layer being applied. From supplier ebay pictures, it is now clear that the same UV driven devices are available in all colours, leading to the question - does this produce an overall increase in efficiency, or is there simply a significant cost saving in just fabricting UV LEDs?.

I've yet to measure the response time of the fluorescent material.


Working with simple optical gear was one of my great pleasures, so I very much hope I can do this again. Optical gear is easier than microwaves. All my kit was home designed and built and the test gear simplicity itself.  For details of my optical work see http://www.g3xbm.co.uk  . G4HJW and others know far more than me in this area. I consider myself very much a novice in this area.

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