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Power supply requirements for Derwent Uniflood LED
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| dewalty |
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Posts: 7
Joined: 21 Jan 2008
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Posted: Sun Jan 04, 2009 10:28 am
Post subject: Power supply requirements for Derwent Uniflood LED
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Hi
Ive got a couple of Uniflood LED Illuminators, however I dont have the power supply. Im struggling to find any tech data on the PSU LED V2, which is the power supply shipped with them.
Do any of you know what the supply voltage is for these units? I understand there is some sort of current limiting switch to allow the illuminators to be in either high or low power. Any help would be much appreciated.
Jay
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| kensplace |
Moderator
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Posts: 1036
Joined: 30 May 2006
Location: UK
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Posted: Sun Jan 04, 2009 12:17 pm
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If they are the same as the ones I got of ebay, which they sound like they are, I had the same problem - nice illuminators but no psu supplied.
Your best bet is to get in touch with derwent to see if they can supply a psu, failing that (if its too expensive, or they wont sell one) then you could try making your own diy psu.
Bear in mind, I am only offering this advice based on my experience with trying to get mine to work, its not known if they will work for as long with my solution as they would with the real psu.
Its also at your own risk both to yourself, others, property, etc if you decide to go ahead - you must ensure you know what you are doing with regards to electrical safety etc before considering going ahead.
However, if you are competant, and can safely do it, here is what I did.
I took a 5amp battery backed up power supply box, which output 13.8v (it was a elmedene psu, normally used for cctv/access control etc) and put in a very large (at least 50 watts) metal clad current limiting resistor (bolted to the metal box for heat dissapation)
If I recall the value was around 4.7 ohms, basically you want to limit the current to under 3 amps as otherwise you will over power the leds and blow them.
I dont know how much more it could take, as I dont want to blow a perfectly good illuminator, but that amount works fine for me.
I passed the current limited power through a outside box with a light dependant resistor controlling a circuit to switch a relay on / off at dawn/dusk so they IR only comes on when needed, meaning the illuminator lasts longer, and does not waste power.
A lot will depend on the cable you use, basically try to keep the power going to the illuminator limited to around 3 amps, around 12ish volts.
Volt drop is a major issue at these amperages, so good cable, and not to long a length is required, you need to take into consideration the voltage drop over the cable when deciding what current limiting resistor to use.
Its not a particularily easy task if you dont have all the bits handy and enjoy tinkering/measuring current/voltages etc, so it may be easier to just buy a psu.
Mine have been running for months now with no sign of any problems or degredation/overheating etc so far.
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| dewalty |
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Posts: 7
Joined: 21 Jan 2008
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Posted: Mon Jan 05, 2009 3:18 am
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Thanks for the prompt reply.
Yes they are indeed the ones off ebay. I did start off with a 4amp supply, which after reading your comments may have explained the problem I had. The heatsinks on the rear of the illuminator got so hot they couldnt be touched for anything longer than a second.
I'm am awaiting a reply from Derwent as to what the supply voltage/current should be. Im not sure how responsive they are to end user tech questions.
I was very pleased with the output coverage considering they are probably near the end of their life.
I did manage to find the consumption for the power supply
50W nominal on full power (external)
40W nominal on low power (internal)
How did you get to the 3amp supply limit? Increasing it or a good guess.
Thanks once again for the reply.
Jay
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| kensplace |
Moderator
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Posts: 1036
Joined: 30 May 2006
Location: UK
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Posted: Mon Jan 05, 2009 3:52 am
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I read about the 40w/50w for internal/external online somewhere, in some specs (pretty much that was all they listed for the specs) and I had a resistor that would limit the current to under 50w, so I tried that.
worked fine, but the resistor was not big enough (size wise, not resistance wise) to disapate the heat.
Popped off to ebay to buy a big metal clad 50w resistor and bobs your uncle, worked fine.
No overheating, either on the lamp, or the PSU.
Back yard lit up as bright as needed (if not too bright!) so I didnt need to try higher current, I could probably go a bit higher, but its fine as it is.
Will take a pic of the intside of the PSU so you can see what I have, and post it in the next few mins.
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| kensplace |
Moderator
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Posts: 1036
Joined: 30 May 2006
Location: UK
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Posted: Mon Jan 05, 2009 4:31 am
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Thats what I have at the moment, you can see the gold coloured resistor bottom left.
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