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Super cheap Dimmable LED Driver (cost under $3)

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Davidwillis Quote  Post ReplyReply Direct Link To This Post Posted: March 14 2011 at 10:20pm
Thanks.... I don't think I explained my thought very well.  I meant to run the voltage regulater into the lm317 to give the correct voltage into the lm317.  Then the lm317 would regulate the current.  I would have to have one for each array (along with the lm317)  It is probably not worth the extra expense though.  Is there a good 24v 1-1.5a power supply for cheap?  Then I could just use a sepearte power supply for each array.




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Post Options Post Options   Thanks (0) Thanks(0)   Quote BnK Quote  Post ReplyReply Direct Link To This Post Posted: March 14 2011 at 10:45pm
sorry this is off topic but what is that coral in the fifth picture that looks like purple flames
Brett and Kristine | Layton, UT | Brett's e-mail: bruno21447@yahoo.com | Kristine's e-mail: oocherryo0@yahoo.com
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Post Options Post Options   Thanks (0) Thanks(0)   Quote seti007 Quote  Post ReplyReply Direct Link To This Post Posted: March 14 2011 at 11:11pm
Originally posted by Davidwillis Davidwillis wrote:

Thanks.... I don't think I explained my thought very well.  I meant to run the voltage regulater into the lm317 to give the correct voltage into the lm317.  Then the lm317 would regulate the current.  I would have to have one for each array (along with the lm317)  It is probably not worth the extra expense though.  Is there a good 24v 1-1.5a power supply for cheap?  Then I could just use a sepearte power supply for each array.




You'll be just fine with 2 to 3 24v power supplies. If you want to do seperate power supplies for each array, you might consider the meanwell eln-60-48d dimmable driver. Although its considerably more $$ it will give you the peace of mind that you have one of the best drivers out there. I seriously considered using it but then in the end the $3 won out over the $35. THere are definately advantages of going with the meanwell but to me the price was a bigger factor.
Someone at RC named spacedcowboy suggested this power supply. Its a great PS for the money but is currently sold out. If you can find something comprable, you can use 2-3 of these to drive all you leds.
 
 
You might also consider the smaller 4.2A supply
 
EDIT:
Just found this powers supply. its a 24v 1.8A with a trim pot for $10.
 
BnK that's a pink/purple birds nest. It was more pink before but has turned a slight purple under the LEDs. I kinda like teh color and growth pattern.
 


Edited by seti007 - March 14 2011 at 11:20pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Davidwillis Quote  Post ReplyReply Direct Link To This Post Posted: March 14 2011 at 11:25pm
I have a couple of power supplies.  But I am not sure if they will work for this.

This one:  http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&_trksid=p4340.l2557&rt=nc&nma=true&item=320655016335&si=Qq8MVSJUqwOyvBJMaN5ZVTXtVmM%253D&viewitem=&sspagename=STRK%3AMEWNX%3AIT

And this one: http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=170604177333&ssPageName=STRK:MEWNX:IT


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Post Options Post Options   Thanks (0) Thanks(0)   Quote seti007 Quote  Post ReplyReply Direct Link To This Post Posted: March 14 2011 at 11:48pm
you could use either to drive leds as long as you have a constant current driver. Looks like the first one may have a trim pot, although i dont see any pics of the front. that would help you tweak the voltage to where you need to be. With the leds i have you could drive 2 arrays of 7 LEDs each at 750-800mA. The second one would be tricky because you'll have to pick the number of leds in the array to have the forward voltage exactly match the voltage supplied by the power supply since its not adjustable.

Edited by seti007 - March 14 2011 at 11:49pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Davidwillis Quote  Post ReplyReply Direct Link To This Post Posted: March 15 2011 at 8:32am
The first one I got does have a trim pot.  So I think it will work well.  I also like that $10 one you found.  At that price I could have a power supply for each array (connected to the constant current driver).  Total cost would only be less than $15/ array 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote seti007 Quote  Post ReplyReply Direct Link To This Post Posted: March 15 2011 at 1:41pm
Originally posted by Davidwillis Davidwillis wrote:

The first one I got does have a trim pot.  So I think it will work well.  I also like that $10 one you found.  At that price I could have a power supply for each array (connected to the constant current driver).  Total cost would only be less than $15/ array 
That sounds good. You would have good control over the color and do a great dusk to dawn effect with each array driven off its own PS.
One thing i just realized is that the voltage drop across the lm317 is 3v and not 1.25 as i stated earlier. I was going off memory but checked my notes and realized the mistake. the 1.25 is the voltage drop across the adj and vout pins:)

Edited by seti007 - March 15 2011 at 5:14pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Davidwillis Quote  Post ReplyReply Direct Link To This Post Posted: March 15 2011 at 10:01pm
So the voltage from adj and vout is always 1.25 v no matter what the resistor is?  And the drop across the lm317 is 3 volts (is this the minimum voltage drop?).
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Post Options Post Options   Thanks (0) Thanks(0)   Quote seti007 Quote  Post ReplyReply Direct Link To This Post Posted: March 15 2011 at 11:26pm
yes and yes. The LM317 keeps the voltage diff between the adj and vout pin at 1.25v that is what allows you to pick a constant current based on the resistor value. The voltage drop across the lm317 is usually 1.7v ( in voltage regulator mode)  but in constant current mode you add the Vref of 1.25v to it which equals about 3v. This woud probably change a bit as the temp goes up. However, in my application since the volatages are matched quite well,  and i have an overkill of a heat sink, mine dont even get mildly warm. So dont worry about the change in temp. BTW. the lm317 has an over temperature and over curernt shutdown. Check out the Pdf for more info.

Edited by seti007 - March 15 2011 at 11:27pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Davidwillis Quote  Post ReplyReply Direct Link To This Post Posted: March 16 2011 at 8:51pm
In my searching, I ran into this:
http://cgi.ebay.com/DC-24V-1A-24W-Switching-Power-Supply-CCTV-LED-Driver-/290498474807?pt=LH_DefaultDomain_0&hash=item43a30ef337

It looks very interesting because it says you can set the current with it.  Would this work?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote seti007 Quote  Post ReplyReply Direct Link To This Post Posted: March 17 2011 at 12:12am
looks pretty good based on the description. It seems to be a regulated current and regulated voltage driver. also looks like you can vary the current and the voltage which is good. The only thing is that its not dimmable without messing with the (probably) a trim pot on the device itself. I wonder if they make a 48v version of it. You could drive twice as many LEDs per array with a 48v version.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Davidwillis Quote  Post ReplyReply Direct Link To This Post Posted: March 17 2011 at 8:44am
I couldn't find a 48v version, just 12, and 24.  If you wanted a dimmer, could you just remove the trim pot, and replace it with a different pot wired to a remote location?

You can't beat that price though.  $10.88 with free shipping, and you have your power supply, and current control for one array.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote seti007 Quote  Post ReplyReply Direct Link To This Post Posted: March 17 2011 at 10:55am
You could remote mount the pot but I would keep the wire length Short because it will introduce Some resistance. Looks like it would be worthwhile to try one and see. You c can make an offer @ $8 or so and see If they take it. I probably won't drive anything above 800mA which would be 80% of its rated Value. Depending on the LED used you may want to drive at a higher current than that so  something to think about. If you do try it keep us posted-
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Davidwillis Quote  Post ReplyReply Direct Link To This Post Posted: March 18 2011 at 9:03am

I put in an offer of $8 for it, we will see.

my leds are: CREE XP-G Cool White, and CREE XP-E Royal Blue

Royal blue:
Wattage:3w
Max Drive Current:1000mA
Forward voltage (@ 700 mA):3.4
Light Intensity: 500mW flux @ 350mA
Dominant Wave Length (max):450nm-465nm
Viewing angle:115テつー-130テつー
Color:Royal Blue
Star Size:20mm
Version:XPEROY-L1-0000-00B01  
cool white:
Wattage:3w
Max Drive Current:1500mA
Forward voltage (@ 700 mA):3.0
Light Intensity:139lm flux @ 350ma
CCT:5000K-8300K
Viewing angle:125テつー
Color:Cool White
Star Size:20mm
Version:XPGWHT-L1-0000-00H51  

It looks like the royal blues could be run with the 800ma, since its max is 1000ma.  But the cool white may need more..??

Edited by Davidwillis - March 18 2011 at 9:03am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote thefu Quote  Post ReplyReply Direct Link To This Post Posted: March 18 2011 at 10:45am
curious as to why a pre-packaged version of this approach has not been made commercially available by the likes of nano-tuners, rapid-led, etc. This intrigues me.

Also, could this solution be easily adaptable to make the dimming happen via a standard 0-10V circuit like used on the Apex Controller?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote seti007 Quote  Post ReplyReply Direct Link To This Post Posted: March 18 2011 at 1:56pm
Originally posted by Davidwillis Davidwillis wrote:


I put in an offer of $8 for it, we will see.

my leds are: CREE XP-G Cool White, and CREE XP-E Royal Blue

Royal blue:
Wattage:3w
Max Drive Current:1000mA
Forward voltage (@ 700 mA):3.4
Light Intensity: 500mW flux @ 350mA
Dominant Wave Length (max):450nm-465nm
Viewing angle:115テつー-130テつー
Color:Royal Blue
Star Size:20mm
Version:XPEROY-L1-0000-00B01  
cool white:
Wattage:3w
Max Drive Current:1500mA
Forward voltage (@ 700 mA):3.0
Light Intensity:139lm flux @ 350ma
CCT:5000K-8300K
Viewing angle:125テつー
Color:Cool White
Star Size:20mm
Version:XPGWHT-L1-0000-00H51  

It looks like the royal blues could be run with the 800ma, since its max is 1000ma.  But the cool white may need more..??
Yeah, i would think you'd want to drive the white LEDs over 800mA for sure. You could do what I did in my design for the White LEDs and have a large power suply driving multiple lm317s.
Thefu, i dont know what type of drivers are used in some of the commercially available lights since i dont own one. My guess is that the lm317 is not as efficient as say a cat4101 based design. However, as i mentioned earlier, for me losing a slight but of efficiency is fine if it saves me a bunch of $$. Right now I have a bunch of blank PCBs for the tripple cat4101 design that are ready to go but I dont think ill be using those since im very happy with this simple design. You dont need an external 0-10v source like with some drivers. the LM317 can be dimmed most simply by varying the resistor. A POT or rheostat of appropriate power rating would work just fine. So, unfortunately, diming usig teh 0-10v out of the Apex might not be an option with this design :(


Edited by seti007 - March 18 2011 at 2:29pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote thefu Quote  Post ReplyReply Direct Link To This Post Posted: March 18 2011 at 2:09pm
No, my question was that if there was a way to take a single MeanWell power supply and power 42 LED instead of just 12 by adding $10 in extra hardware, why have they not made such a box available? I was not speaking about commercial fixtures...nano-tuners and rapid-led both sell parts to DIYers.

Also, I know that you don't NEED a 0-10V source, but what if you DO want to control these with a controller like and Apex? How could you adapt it for that.

Also, comparing $3 to a $30 meanwell ELN-60-48D is not apples to apples because with the $3 you still have to buy some pwer supply, right? The savings really comes in when you are doing very large arrays, where you have one power supply and three or four of your circuits powering 7 LED, right? Then, instead of three meanwells to do 36 LED, you use one meanwell and 5 of your circuits to do 35 LED. That would be $90 vs. $45, right? With the main difference being that I could not dim them with a controller.

Just trying to understand the application, the numbers, and the differences when you do it this way.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote seti007 Quote  Post ReplyReply Direct Link To This Post Posted: March 18 2011 at 2:35pm
Originally posted by thefu thefu wrote:

No, my question was that if there was a way to take a single MeanWell power supply and power 42 LED instead of just 12 by adding $10 in extra hardware, why have they not made such a box available? I was not speaking about commercial fixtures...nano-tuners and rapid-led both sell parts to DIYers.

Also, I know that you don't NEED a 0-10V source, but what if you DO want to control these with a controller like and Apex? How could you adapt it for that.

Also, comparing $3 to a $30 meanwell ELN-60-48D is not apples to apples because with the $3 you still have to buy some pwer supply, right? The savings really comes in when you are doing very large arrays, where you have one power supply and three or four of your circuits powering 7 LED, right? Then, instead of three meanwells to do 36 LED, you use one meanwell and 5 of your circuits to do 35 LED. That would be $90 vs. $45, right? With the main difference being that I could not dim them with a controller.

Just trying to understand the application, the numbers, and the differences when you do it this way.
That is very true Thefu, maybe another reason why most commercial applications as wella s most DIY designs dont use this design. Im my case, My initial design using the cat4101 had dimming pots but I always had it running at max current so i decided not to incorporate dimming with this design. I guess if i had an Apex, i would have chosen a different design to do dimming. It really makes it slick to be able to do dimming with a neat controller like the Apex. You could do some neat cloud and lightnign effects that way.
You are also the savings from this design. the bigger the build the more you would end up saving. You would still need a power supply to drive the lm317. But a $40 power supply can drive quite a lot of LEDs. eg, you can drive 100 LEDs with a couple of the power supplies I used.
BTW, if you are interested in a cost effective way to use the 0-10v from the Apex, look at the cat4101 design. You may have better luck than I did. There is a huge thread about it on RC. I can help you if you need it.


Edited by seti007 - March 18 2011 at 2:50pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Davidwillis Quote  Post ReplyReply Direct Link To This Post Posted: March 19 2011 at 9:34am
I am just waiting for my LED's to show up.  It looks like they are delayed.  But I was wondering, what size, and where did you get the Aluminum T material to mount your LED's on.


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Post Options Post Options   Thanks (0) Thanks(0)   Quote seti007 Quote  Post ReplyReply Direct Link To This Post Posted: March 19 2011 at 11:31am
I found those particular ones at NPS market square store. They have since sold out of that particular type but have others like aluminum U channels that would work just as well. You can often find some pieces that are sold by weight so that would make for a real cheap heat sink. The ones i got came in lengths of 8' that I cut down to 36" length.
The double sided thermal tape is this one from ebay. It makes the job of attaching or detaching LEDs real easy:


Edited by seti007 - March 19 2011 at 11:34am
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