Author Topic: Cheap switching power supply from ebay  (Read 2087 times)

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Offline triond

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Cheap switching power supply from ebay
« on: December 29, 2016, 07:46:39 am »
Hi
so to light up some led,


i have been thinking a few 100 watt led,
like this one http://www.ebay.com/itm/NEW-100W-Cool-Warm-White-High-Power-LED-Panel-Chip-9000LM-100-Watt-Lamp-Light-/262303267153?var=&hash=item3d127e3951:m:mDDISnNuoQwc4oKzWyVHalg
100 watt 36 volt,

connected directly without resistance to that 400w power supply (about 36v 11 amp http://www.cafr.ebay.ca/itm/AC-110V-220V-to-DC-36V-400W-11A-Switch-Power-Supply-Driver-Adapter-For-LED-Strip-/291915092102?hash=item43f77ed086:g:YaoAAOSwpLNYBiuq

so in clear the question is is it safe to connect directly the led in parallels with nothing else,

and how trustable chinesse switching power supply  are,


 

Offline bills

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Re: Cheap switching power supply from ebay
« Reply #1 on: December 29, 2016, 08:15:26 am »
The power supply would not be the problem, the crappy led would be. :palm:

Never argue with idiots. They drag you down to their level and beat you with experience.
 

Offline Seekonk

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Re: Cheap switching power supply from ebay
« Reply #2 on: December 29, 2016, 09:51:23 am »
I don't think it would be so bad to spend a couple bucks and learn something.  You'll get a lot of comments, most of it will be regurgitation.  I wish I had a picture of a 30W Philips DLM LED lamp I own. It has a 7 pound aluminum heat sink.  I drive a lot of LED pure voltage, but only at a small percentage of their rating and from sources that can't supply much power.  And I'll drive them in parallel.  Drive them at much lower power and they will be a lot more efficient.  None of this will sink in till a few of them burn up and I think a few bucks to get an education is money well spent.
 

Offline mpicker21

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Re: Cheap switching power supply from ebay
« Reply #3 on: December 29, 2016, 01:33:28 pm »
I agree with the above. Learn away, but consider putting current limiting resisters in. It might work without. But you are more likely to notice differences in intensity of your LEDs. The resisters will ensure each one uses the same amount of current. Let's say you get 4 and hook them up without resistors. If they aren't all exactly equal then one or two will use more current than the others, thus pulling more than they are rated for.
 

Offline Fungus

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Re: Cheap switching power supply from ebay
« Reply #4 on: December 29, 2016, 04:55:20 pm »
so in clear the question is is it safe to connect directly the led in parallels with nothing else,

No.

and how trustable chinesse switching power supply  are,

Usually OK, but take the current rating with a big pinch of salt.

11A is the maximum current for a short burst. Don't imagine it will run at 11A, 24/7/365. It won't.

Usually I buy at least twice the current rating I actually need. That way it has a chance of survival.

PS: Make sure it has good ventilation, no power supply is happy in an enclosed space.
 

Offline Siwastaja

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Re: Cheap switching power supply from ebay
« Reply #5 on: January 04, 2017, 03:01:59 pm »
Contrary to the auction title, that PSU is not an LED supply at all (a constant current supply), it's a constant voltage supply. You cannot use it to drive LEDs directly. There are Chinese Ebay LED supplies (constant current supplies!) also available, and they work OK when properly cooled, at least for some hundred, maybe 1000 hours.

Those kind of Ebay LEDs are sometimes OK, sometimes not. Often, they provide much less light than specified, mostly generating heat, approaching incandescent light bulb efficiency levels. But sometimes you are lucky and get a usable LED with possibly near 70-80 lm/W.

If you want to play around with the Ebay stuff, I'd recommend you get that kind of 100W LED, and buy a 50W constant current LED driver for it.  Then, it will drive your LED at only 50W, increasing the lifetime and efficiency a lot. Be careful with the mains powered stuff, they can be, and often are, fatally dangerous. Mount the LED to a good fan-cooled heatsink, like something bigger designed for power-hungry CPUs. Mount the PSU so that the fan cools it down, too, then you have decent chances of the elcaps lasting for more than a few hundred hours.
« Last Edit: January 04, 2017, 09:26:14 pm by Siwastaja »
 

Offline Kjelt

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Re: Cheap switching power supply from ebay
« Reply #6 on: January 04, 2017, 03:07:46 pm »
Those high power leds consist of many many tiny leds in series inside.
Often one ore more are dead already and the rest will start to follow soon.
For these prices you get B grade garbage can stuff.

Do you really need that much wattage in such a small housing? If not choose medium power leds (100-200mA) they have higher efficiency do not need so much cooling and will last 30000+ hrs.
All office lighting uses these kind of leds, high high power leds are only used for discotheque (DMX) lighting or spots and they use a lot of metal (sometimes with fan) to keep the led cool.
 

Offline Fungus

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Re: Cheap switching power supply from ebay
« Reply #7 on: January 04, 2017, 04:19:12 pm »
For these prices you get B grade garbage can stuff.

In my experience it's a lottery, about 50:50 on the Big Clive test. Nothing to do with particular sellers.

I always buy a couple of batches which are slightly above the cheapest possible price and cross my fingers. Usually I get a good batch and it's still cheaper than buying from a 'reputable' source if you only need small quantities.
 

Offline Kjelt

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Re: Cheap switching power supply from ebay
« Reply #8 on: January 04, 2017, 09:22:12 pm »
If the price would be conform to market minus 25% I would agree with you.
$3 for a decent 100W led I don't think so, if it is not B grade from a decent manufacturer it probably is from a non decent manufacturer or low quality/efficacy. Look at the flimsy metal carrier, rediculous.
Look at comparison to Cree or Osram 50W modules costing $40 with multiple protection methods such as ntc on the board for the driver to shut down or lower the power to save the ledmodule.
But hey if you want to burn down your house go ahead have fun.

Still i don,t see why you would like such an enormous wattage in such a small space, it is asking for problems or short lifespan. All the big lighting companies that need high wattage led like stadium, street and other 100s Watt lightsources use max. the 1A (3W) leds spread on good heatconducting pcbs and lenses. None use this stuff, because you need watercooling or heatpipes to keep these things cool.
« Last Edit: January 04, 2017, 09:26:20 pm by Kjelt »
 


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