High Power LED wiring from a Driver

[jesserose85]

Hey Guys,

I am setting up two high power LED units (each one consists of 3 LEDs) link is here Green 3-Up EndorStar - LED Supply.com I am running a 12V 1500mAh battery pack. The driver I am using is a 1000mA Buck Puck link is here: 3021-D-E-1000 BuckPuck - LED Supply.com

I was planning on wiring these in Parallel until I came to this forum and noticed a lot of regular contributors mentioning that Parallel wiring of LEDs is a BAD idea.

Basically I just need to know the best way to get wire these babies up so I can get maximum power.

Also, is there any way I could integrate this product into my setup **broken link removed**

As I mentioned in my last post I would like to be able to control the LEDs.

Thanks a lot people I really appreciate the help.

Jesse Rose

 

[Sceadwian]

Try searching the forums, or Google, this topic has been covered in EXAUSTING detail, many times here and elsewhere. If you spend a few hours looking into it yourself and post back here if you still can't figure out what you should be doing post your questions about the information you found, and we'll help you then. You do your research first and people here will bend over backwards to help you.

If you have trouble finding the information you need post your problems here and the search terms you used, searching is an art in and of itself and using the wrong terms could get you a dead end which again I'd be glad to help with, so would many others, but we all get short tempered repeating the same information over and over again, so posts like this will tend to get ignored unless someone's really bored.

 

[jesserose85]

I have spent plenty of time looking around and I think I have a decent idea of the wiring schematic. I was just unsure as I couldn't find anything exactly the same as my situation. All the LED wiring tutorials I looked at use resistors and mostly pertained to regular LEDs, not high powered ones like I am working with. My understanding is that I don't have to use resistors due to the fact that I am using a driver. I was also a little confused because the guy who sold me the LEDs informed me to wire in Parallel, then I come to this forum (which I trust a lot more that the guy) and I see numerous posts warning against wiring LEDs this way.

I am sorry if I it seems like I am beating a dead horse but this is a very expensive project I am working on and I want to make sure I have it right. I will most definitely post some pictures on here when I am done (mid-late Jan 11)

I also wasn't sure about the product I mentioned earlier being able to be used with my setup.

Thanks again and sorry for not being more specific in my initial post. I can understand how that might piss the regs off.

Cheers and Merry Christmas

 

[Sceadwian]

You're not actually working with an LED, you're working with an LED module.

Each module you have is already three LED's in series in a single unit which is why it's a module. Even if they're very close in their production dates the total forward voltage drop between any two modules will never match so well that you can safely drive them in parallel, on cheap devices you'll see LED's (matched or not) driven in parallel, they always fail over time.. Each of your modules should have a separate drive circuit period; you could manage it with resistors to help balance the current to each string but that will not be the way you SHOULD do it.

The 1amp max current for the LED modules you listed is the MAXIMUM current, meaning you'll experience shorter life at that current and at elevated temperatures the units will fail no matter what. If you run two in parallel at the drivers max rated current using 10ohm ballance resistors you might be okay. But you should really run each module on a separate driver. Keep in mind, you NEVER EVER run an LED module or driver at it's maximum rated current, those are right near their failure points, you have to derate unless you want this to fail in a few weeks, months, or during a bad summer day.

 

[audioguru]

The three LEDs in a module are completely separate, not connected in series. The datasheet does not show which terminals are for which colour.

 

[Sceadwian]

AG, you might be reading the wrong PDF. The links I followed were to white LED modules. He needs to specify the EXACTY model of the LED module he has for clarification.

 

[audioguru]

He is looking at RGB audio controllers to drive his 3-colours LEDs as a Colour Organ.

 

[jesserose85]

Sorry guys. The light I'm using is the 3up GREEN model. I believe the 3 LEDs on each module are connected in series, because the positive and negative terminals are connected on TWO of the terminals.

I am thinking that to put the two modules in a series, I run the positive from the driver to the positive on module 1, then the negative on module 1 to the positive on module 2, then the negative on module 2 back to the driver.

The whole reason I got the 1000mA driver was because the guy that sold these to me told me to wire in parallel, thus giving each module 500mA.

As Sceadwian said, running the Modules at 1000mA in series will not be a good idea, so I guess I kinda screwed myself by getting the 1000mA driver

I do have a potentiometer attached to the driver though, would turning it down to say half way limit the mA to each module enough to operate safely?

AG sorry for the confusion with the RGB controller, I do only have green LED modules, I just thought I could use the controller for the audio and strobe effects.

Thanks again guys, I have attached a picture of what I am making.

Jesse

 

[nickelflippr]

Sorry guys. The light I'm using is the 3up GREEN model. I believe the 3 LEDs on each module are connected in series, because the positive and negative terminals are connected on TWO of the terminals.

I am thinking that to put the two modules in a series, I run the positive from the driver to the positive on module 1, then the negative on module 1 to the positive on module 2, then the negative on module 2 back to the driver.

You will need a supply voltage twice the forward module voltage + the 2V overhead of the BuckPuck. So at 700ma drive that would be 2 x 10.2V + 2 = 22.4V minimum.

The whole reason I got the 1000mA driver was because the guy that sold these to me told me to wire in parallel, thus giving each module 500mA.

As Sceadwian said, running the Modules at 1000mA in series will not be a good idea, so I guess I kinda screwed myself by getting the 1000mA driver

I do have a potentiometer attached to the driver though, would turning it down to say half way limit the mA to each module enough to operate safely?

You are O.K. here. The "E" model with the external pot controls the current per the data sheet, which also shows the hookup schematic. The pot voltage must overcome the CTL voltage threshold of 1.65V and the module shuts off at 4.2V. Look at the chart for the CTL(V) vs. Output Current(A) relationship.

AG sorry for the confusion with the RGB controller, I do only have green LED modules, I just thought I could use the controller for the audio and strobe effects.

Thanks again guys, I have attached a picture of what I am making.

Jesse

You got some big heatsinks for those 3-up stars? That's 10+ watts max of dissipation for each module. Get some thermal grease for the back of the stars too if you don't already have some. I have 3 x 1W stars on a 3x2 chunk of cpu heatsink, and it gets toasty warm (not hot). You may end up needing a fan for this.

Huh, the BuckPuck data sheet seems happy to point out parallel strings of leds in their sample hookup diagrams. The fact that there is a current feedback loop, should preclude one string from drawing more current then the other, up to the amount of ripple current (+/-5%). Normally, I would think the caution against led parallel string operation would be for a constant voltage source.

 

[jesserose85]

I have an old Pentium 3 heatsink (the big rectangular ones) that I am going to cut up an attach to each module with some arctic silver thermal compound that I picked up.

What are your thoughts on Figure 3 in the Buckpuck data sheet? The series parallel array should give me 500mA to each module right? It shouldn't get to warm at only 500 I would think.

 

[Diver300]

Paralleling LEDs is not a good idea. I've seen it done where it works, and I've seen it done where it doesn't. The problem is that as one bank heats up, its voltage drops so it takes all the current so it gets hotter.

I suggest that you put the LEDs in series and wind the adjuster pot down to 500 mA.

If you can't do that, put a resistor of 1 or 2 ohms in series with each string. The values in each string must be the same. The more resistance, the more stable, but the hotter the resistors get.

 

[jesserose85]

Yes I see what you are saying. I just find it peculiar that the data sheet for the Buck Puck has its wiring diagrams in parallel after everything that has been said here. With that said, won't my 12v 1500mAh lithium battery pack now be insufficient to supply the two banks wired in series?

 

[nickelflippr]

Late night fuzzies on the current in the parallel strings, which is based on the Vf of the leds, but Luxeon claims a +/- 0.06V tolerance (less than +/- 2% at rated current). In my mind if the led current is underated at 500ma, then I don't see much downside to the series/parallel circuit. I don't have long term experience to back that up, but I find it hard to believe that an extra 10-20ma (tolerance) spells trouble for these rather stout Rebel leds. Anyone?

Based on my Apple cpu heat sink, you would need the full heatsink for just one module, but that's just a guess. If the module is not going to be in free air then you still might need a fan.

Diver300:
Were the parallel led strings high quality (like the Luxeon), high power, current limited, such as these will be?

 

[jesserose85]

Quick simple question: If wired in parallel, these two will draw 1000mA from the driver between them (500+500), If my 12V battery pack is rated at 1500mAh, Is the calculation as simple as 1500/1000? If so I guess I'll need a bigger battery because I'll need a little more than an hour and a half out of these.

Thanks for all the help, I'll be sure to get back with some pictures and results of how everything came up. It'll still be a while, it's a big project

Cheers & Merry Christmas

 

[audioguru]

You need to look at the details of your battery.
If it is a lead-acid 1500mAh one then it supplies only 75mA for 20 hours. It might supply 175mA for 8 hours, 300mA for 3 hours or 600mA for 1 hour. It might not be able to supply 1500mA.

 

[ronv]

The driver module is constant current so you may be ok with two sets of 3 in parallel.

 

[jesserose85]

It's Lithium Ion Rechargable. Where do you get the 600mA for 1 hour from AG?

 

[MikeMl]

The driver module is constant current so you may be ok with two sets of 3 in parallel.

What stops the set of three with the lower Vf from hogging all the current?

 

[ronv]

If they are matched by .06 v as per NF neither will get all the current. The constant current supply helps the thermal runaway issues, and even if one got it all it would still be in spec. Perhaps not the best way to do it but not a disaster either.

 

[MikeMl]

If they are matched by .06 v as per NF neither will get all the current. The constant current supply helps the thermal runaway issues, and even if one got it all it would still be in spec. Perhaps not the best way to do it but not a disaster either.

You are right. Look at the attached sim for 1.6A Lumileds.