Author Topic: Playing with some 7 watt LED's  (Read 5449 times)

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Mary B

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Playing with some 7 watt LED's
« on: August 06, 2015, 09:47:20 PM »
I picked up these LED's on sale cheap($3 each) so I started playing with them. They have to be heatsinked and I started digging in the junk box. Ran across a CPU cooler minus the fan... fan would have been 12 volts anyway so no good... each LED is 24 volts at 300ma, 500 lumens. I had some 24 volt small fans so I used the wire tie trick to mount them(poke one through the heatsink and through the fan holes. Put another on like putting a nut on a long bolt). I used some adhesive thermal pads to mount the LED's and a buck driver that maintains constant current.

LED's http://www.mpja.com/500-Lumen-7-Watt-Super-Bright-Warm-White-LED/productinfo/32077%20OP/
Used a constant current driver from this page http://www.ledsupply.com/led-drivers/buckpuck-dc-led-drivers went with the 700ma driver, the LEDS can handle a little extra current considering they will be on momentary. This will be a replacement for the front door flood light that eats bulbs...

Got everything mounted and wired, ran it without fan and the heatsink rapidly climbed to 165f... to hot! Added the fan and dropped it to 85f! Much better! Only problem will be making some holes in the light fixture for airflow... it is your typical pot metal flood.





Bruce S

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Re: Playing with some 7 watt LED's
« Reply #1 on: August 07, 2015, 07:17:35 AM »
WOW 7 watt! I thought the 3 watt units Rich H built were bright!
Will you need sunglasses on when working with it  8).
Those heat-pipes are the very reason I dig around for older Dell computers!
Too bad you couldn't pipe the extra heat somewhere when winter sets in.
Looking forward to a pic of it working.
Everytime I try to use my digital camera, the LEDs mess with the flash.
Best Of luck,
A kind word often goes unsaid BUT never goes unheard

Mary B

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Re: Playing with some 7 watt LED's
« Reply #2 on: August 07, 2015, 04:53:30 PM »
My camera(cell phone) refused to take a picture with it on! Popped a notice saying to bright. It easily lit a 16x14 foot room and I would put it at the same level of brightness as a 150 watt bulb.

Mary B

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Re: Playing with some 7 watt LED's
« Reply #3 on: August 08, 2015, 09:26:37 PM »
Built the second one took a couple more pics

Camera did not like this and tried to shut down!



Pointing into my living room, camera f stop was wacky, it is brighter than it looks


XeonPony

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Re: Playing with some 7 watt LED's
« Reply #4 on: August 10, 2015, 01:13:19 PM »
starting to feel like the 10 and 20w ones I play with are a bit over kill then?
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Mary B

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Re: Playing with some 7 watt LED's
« Reply #5 on: August 10, 2015, 04:44:56 PM »
For indoor use I would rate a single 7 watt equivalent to about a 60 watt bulb... maybe 80 watt... the bigger ones would be great outdoors or for really large rooms! The take a big heatsink!

DamonHD

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Re: Playing with some 7 watt LED's
« Reply #6 on: August 11, 2015, 09:20:29 AM »
My hall and small rooms have 7W LEDs, some bigger rooms 10W, bed-side lamps as little as about 2.5W I think.

About 1/10th or less than I used to have in old incandescents, eg when I was a kid.

Rgds

Damon

Bruce S

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Re: Playing with some 7 watt LED's
« Reply #7 on: August 11, 2015, 09:25:40 AM »
That seems about right. When Rich H installed them in the school house in Upper Pulau , he put up 3 and they lit the whole room up.
3-3watt LEDs

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Harold in CR

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Re: Playing with some 7 watt LED's
« Reply #8 on: August 11, 2015, 12:01:26 PM »

 When MaryB talked about needing huge heat sinks for the 7 watt LED's, what is the total amount of electricity used, including all that lost heat ?  Can't believe it is all 7 watts total ?

Mary B

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Re: Playing with some 7 watt LED's
« Reply #9 on: August 11, 2015, 05:38:29 PM »
Running a pair of them at 350ma each(700ma total at 24 volts 16.8 watts)  took the heatsink to 165f without a fan. Fan drops it to 5f over room ambient. They do create a lot of heat for some reason. There are 14 or 16(hard to count) led junctions in each 7 watt led.

"Between 2012-2014 LED efficiency jumped from just over 60 lumens per watt to nearly 100 lumens per watt, and they may hit 150 lumens per watt by 2020. Compare LEDs to compact fluorescent lights (CFLs) with 55-70 lumens per watt, and traditional incandescent bulbs with 13-18 lumens per watt, and the LED advantage is bright as day." so only about 50% of the energy goes to light production, rest is wasted heat... http://cleantechnica.com/2014/11/05/led-lighting-efficiency-jumps-roughly-50-since-2012/ the heat pipe heatsinks are designed for fan use to keep the pipes cool. A traditional heatsink with more mass would also work to keep them cool. And since I am running these a bit over current spec the cooler I keep them the longer they will last. Also the cooler you keep an LED the more efficient it is at creating light. About a 10% lumen output difference between running at 165f and 85f according to charts I found somewhere...
« Last Edit: August 11, 2015, 05:46:36 PM by Mary B »

Mary B

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Re: Playing with some 7 watt LED's
« Reply #10 on: August 11, 2015, 06:16:15 PM »
Test setup:
Single 7 watt LED on what is supposed to be a 10 watt heatsink. Adjustable constant current dc/dc converter. Current measured with a digital meter.





Temp stabilized at 140 degrees running at rated current of 300ma, was still climbing when I took this



I had to drop the current to 100ma to get the temps to fall back to a more reasonable 108 degrees! Fans are a must to move heat off these if you want the longest life. Doesn't take a lot of air. Fans I am running draw .07 amps. The dual LED setups are drawing an actual current of 628ma including fan and they run 5f over ambient temps.


Harold in CR

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Re: Playing with some 7 watt LED's
« Reply #11 on: August 12, 2015, 08:41:30 AM »

 MaryB, thank you very much for explaining how the LED's consumption is figured, including the fans and heat waste.

 Let me explain my problems with electronics and milliamps.

 I was involved most of my life with 120-240V at up to 60Amp usage. Home and light commercial wiring/troubleshooting, AND, a lineman for a New Jersey Power Co, at up to 7200/12,500 V, live handling. Making those kinds of systems do what was needed, was no problem.

 To put that in electronic mode, I'm a welder, not a solderer. Used to be, didn't matter what the current draw was in a specific application. 

 Now, trying to save every tiny bit of energy because of high power company rates (30 cents Kwh here) and constant outages, (2 since I started typing this response) fridge compressor is twisting in it's frame, trying to restart-restart-restart, etc. UPS on the computer beeping, and, if turned on, TV cutting out, restarting, as many as 3-4-5 times in just a few seconds, span, is why I am about to hook up an off grid wiring system in my house.

 I do have a few LED strip lights made up, by wrapping a section around a white plastic bottle, that I have soldered a standard screw in light bulb or screw in Fluorescent bulb base, and screwed them into flat base light sockets for ceiling lights or pigtail sockets for temp lighting, especially over my computer desk.

 Too much hijacking on this thread. I will start my change over thread in a few days.

 Thank you again, MaryB.

 Harold in CR

Mary B

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Re: Playing with some 7 watt LED's
« Reply #12 on: August 12, 2015, 05:31:58 PM »
No hijack, on topic! Easiest way to think of ma is 100ma is .1 amp

Johann

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Re: Playing with some 7 watt LED's
« Reply #13 on: January 04, 2016, 06:22:33 PM »
Mary,
What is the difference in power consumption between the ones you use and those used in LED screw-in bulbs where they use 14 tiny LED's.
Which would be better?

Mary B

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Re: Playing with some 7 watt LED's
« Reply #14 on: January 04, 2016, 07:08:31 PM »
basically the same, these have 14 led dies in them.