need help with buck puck wiring.....

[jason 77]

Hello everyone.... I need some help in understanding how to wire up some high power LEDs to the Buck Puck driver I bought.... I tried searching but just ended up with a headache.. :shrug:

I bought 16 "lumiled's" off ebay for 24 bucks from a thread on this site "thanks for the heads up by the way"

I bought 2 1000ma buck pucks off of ledsupply.com, I bought the 1000ma ones because they were the same price as the 350ma and 700ma so I figured it was a better deal...

But now that I think of it.. if I hook up the leds to the buck puck like the schematic shows 3 in series 3.42 vdc X 3 = 10.26 volts which is fine but the leds are rated at 350ma... will the 1000ma buck puck over drive these leds since they are rated at only 350ma?

I think my dyslexia is getting the better of me right now..

 

[kuksul08]

You could wire them in parallel, but if one of the leds has a higher Vf (since they are not all created equal), it will take more current. That could potentially burn it out, or just make the 3 LEDs not all equal brightness.


Maybe the lumileds will take 1A though... I dont know. I had a luxeon lxhl-mw1d that I ran at 1A for a little while. It got really really hot quickly, but shined bright white... you will want to wait for more responses about that though

 

[gillestugan]

What source are you going to drive them from. 12V? You should try to put as many as possible in series, as this will equalize differences in Vf that may cause one string to get more current than the others.

I think you will be just fine connecting them 3s3p.
The puck will rise the output voltage to a level where total output is 1000mA , regardless if the leds only can manage 350. But if you connect 3 strings in parallel you will be fine as long as the variation in Vf between the strings is small enough

I have one of those wharm white 1A luxeons. (bought 3,5 years ago) It started to change colour at 850mA so I wouldn't try to drive it att 1000. 500mA works fine as long as it is heat sinked. It's not bright but has a nice tint.

 

[jason 77]

Thanks for the responses guys!....

I was planning on using a 19Vdc 4.7A laptop power supply as I have a bunch I got for free...plus they are a nice small size...

So if I ran two sets of 3 leds in series off of the 1000ma buck puck, it should be fine right? I can figure out the voltages, it is just I am not used to having to factor "constant current" into the equation...

 

[SafetyBob]

That should work. 3 series in 3 parallel strings.

Just try this, take measurements if you like just for information might be nice.

Don't be surprised if your laptop power supplies start dying after awhile. I have tried it twice with maybe a month of 12 hour a day runs before they died.

May happen to you, may not. If they do work and work well, please come back and tell us what make and model you are using. It is never a bad thing to know exactly what does work!!

Bob E.

 

[jason 77]

Thanks SafteyBob.....

I am going to build a led array for my fishtank, it will be one for about 12 hrs a day. I will report to you guys how these laptop power supplies hold up.

 

[jason 77]

On a side note/thought... if these laptop powersupply's prove to be limited in their life span being used as LED drivers.... Would the Buck Pucks that are listed as being able to take AC power as their input, be a better choice?

 

[SafetyBob]

There are some that can take AC power, but you would have to blow money on a transformer to lower it to 24 or 32VAC (as memory recalls), so you would still be better of to get one the a advance transformers or MicroDrive9 or something like that already made.

If you have enought laptop power supplies, and they die without taking anything else with it, for economy sake, just keep using them until you are out.

Bob E.