100W red LED driver

[Rachie]

I'm designing a science project which uses an ultra bright red LED in order to illuminate flesh. I'm considering using a 100 Watt LED from ebay, possibly with a lens kit. The problem is I can't find a suitable driver. Everything seems geared towards blue/white LEDs with a voltage range of 25-36 V, while the red modules need 20-24 V.

I'll need rudimentary dimming capabilities as well. PWM is fine, DMX would be great if it's affordable. This one looks promising, especially since I already have a couple 12V 18A power supplies, but it doesn't specify the output voltage range. Does anyone have suggestions?

Thanks,
~Rachie

 

[spencer]

You get what you pay for with LEDs. Cheap Chinese junk is, well, cheap and junky. Also, there is NO WAY that this LED will put out 6000 lumen at 100 watts. Another thing about the cheap LEDs, they lie on the specs. While it may work for your application, I would suggest a higher quality alternative, the Luxeon Rebel.

They are also much easier to power as you can use multiple drivers if you need and can wire the LEDs any way you want (series, parallel, S/P). They will also be considerable easier to provide heatsinking for as multiple emitters spread the heat over a larger area. They are more expensive but will cause less headaches in the long run.

 

[Illum]

Illuminate flesh with 100W of Red? You mean simulate flesh?

 

[IMSabbel]

Avoid that LED. Both picture and description are taken from a white LED (as you can easily see from the phosphor), so who knows what else is wrong with the offer.

As for driver, take a look at the hyperboost from taskled:

http://www.taskled.com/hboost.html

It might been a bit of cooling (i.e. thermal pad to a heatsink) if really driven up to that level ,but according to the specs it should do.

 

[Hoop]

Go with a RED module from Luminus. PT-120. Runs at 2.6 volts nominal, 3.4 max, so power options would be to direct drive off of rested lifepo4's in combination with a high wattage resistor. Lifepo4 voltage curve would be pretty flat @ 3.2 volts so you could get consistent output during discharge. Use large headway cells in parallel, or just one. Use toggle switches in combination with different resistors for multiple output levels. Could have two output levels per switch using three way toggles. Mount the LED to a pc heatsink. You could power a 5 volt pc fan with a single lifepo4 cell as well using a 3 to 5 volt boost circuit.

 

[Rachie]

I suppose I should give more details of what I intend to do.

I want to make an interactive museum kiosk allowing patrons to place their hand on a pedestal with a small round window, with the LED array mounted under it. The LED will then ramp up to full power, allowing them to see the bones and veins inside their hand. I've tried this with smaller LEDs, and the effect definitely works. I have ~$100 in funding for the LEDs and driver, so I want to do it right.

The most important factor here is bulk photon output in a fairly small package. Size and efficiency don't matter, as it will be line powered, and in a large box. I'm already prepared to use a big CPU heat sink and fan, and possibly peltier junctions if needed. I also understand the safety aspect of not blinding or burning people, and will take this into account. I'll chill the glass window if need be.

Luxeon rebels will work if I can find an easy way to mount a dozen or so of them to a heat sink. The Luminus module was the first one I looked at. It's definitely nice, but much more expensive.

I admit I was tempted by the cheap Chinese LED. I have a white version I've been playing with which seems extremely bright, but I have little to compare it to. I suspected the specs are exaggerated, but I don't know by how much.

 

[Hoop]

I wouldn't worry about the light from the LED burning anyone's hand because LEDS do not put out much infrared at all. I wonder if a red filter in front of a standard white LED would accomplish the same task as a red led in this instance?

 

[hank]

Try a google image search for transilluminate hand -- I tried this years ago and when I started asking why the results weren't sharp, learned that body tissue is (optically) more like pudding than like jello -- it will light up, you can get shadows to some extent, but you aren't getting a clear shadow like an X-ray gives.

Here are a couple of examples I found with a few minutes' searching, you can certainly do better if you look harder than I did:
http://medgadget.com/2012/02/battle...-shows-off-veins-when-the-lights-are-out.html
(notice the flesh behind the veins is glowing like fog, not like clear jello; this is infrared, and the blue (low oxygen) blood in the veins makes clear shadows because the veins are right under the skin).

Red LED -- same basic result here: http://vimeo.com/9600772

earlier at CPF: http://www.candlepowerforums.com/vb...o-see-veins-in-a-patients-arm-Yes-thats-right

 

[Rachie]

A filter on a white LED would probably work, but why waste most of the light, and heat up the filter? White light alone does work, but wavelengths shorter than red-orange are almost entirely absorbed, causing needless heating.

The images are exactly what I expect to get. Nowhere near the quality of a fluroscope, but still neat to look at, and can't give you cancer. I even have a picture of my own hand when I tested some infrared LEDs:

If red light doesn't give a good enough effect, I might switch to infrared with a camera and monitor.

 

[HarryN]

I have used the effect you are talking about for fun - looking into my hand with a red led. It is a neat idea.

100 watts is still a fair amount of power though, so don't assume that the top of that LED will not be hot.

Since you have AC available, there are plenty of driver options. Worst case, if the driver output voltage is too high, then just add a power resistor in series. Driver options include meanwell, Advanced Transformer, magtech.

http://www.ledsupply.com/

http://www.ledsupply.com/lp1090-24-170.php

In addition to my favorite LED, the Rebel, some other possible suppliers are LED Engin and Bridgelux.

http://www.ledengin.com/products/emitters

http://bridgelux.com/

The trick is to find the right combination of optics and LED package to obtain the needed flux density / lux level.

I don't think you are going to get 100 watts for $ 100 though, the driver alone is that much.

25 watts might be a better target for your budget.

 

[Epsilon]

A user on CPF Market place sells the Luminus PT54 in red for next to nothing (10 leds for 65$):
http://www.cpfmarketplace.com/mp/sh...hipped-Or-W-Heatsink-amp-Optics-14-Shipped-US

That is rated ~2.7v and 9A for around 450lumen red. I just finished building a light with that led and it just rules :D. Allthough I can not look through my hand (just tried, the tissue diffuses all light and so the light travels around bones thus making them invisible). But maybe a more linear beam (with lenses) will help.

You can drive a few (6*2.7v =16.2v) of these in series with a Der Wichtel 9A driver:
http://www.candlepowerforums.com/vb...icient-5A-9A-Buck-Converter-for-SST-50-SST-90

So it totally is possible to get to 100W for 100$ :).

That way you can easily over 100 and have quality stuff :).

 

[Dplight21]

Red LED is correct to use for better effect. Red color is identified easily. And I suggest to 25 Watt for the project. 100W is more expensive than it.

 

[Rachie]

I'll probably get the luminus LEDs as soon as I get approval from my purchaser. I might simply drive them with my 12V power supply and a beefy resistor. Horribly inefficient, but I don't know if I'll be able to afford both the LEDs and a good controller. The powerbuck looks rather underpowered for this.

 

[Rachie]

I'm back, and this time with a bigger budget. I now have $1000, and possibly more if I really need it.

I bought six of the PT-54s, and three big CPU heatsinks with fans connected together to cool them. Probably overkill, but I want this thing to last. They're still in transit.

Any better suggestions for a power supply? The ones linked don't have anywhere near the current for the PT-54s: 8 A continuous, or 13 A at 25% duty cycle.

I'd also like to build an infrared version. Does anyone know of nice powerful IR LEDs? I'm almost tempted to use a 5 W laser with a carefully controlled wide beam for low power density, but it seems a bit too dangerous.

What wavelength should I get? How about a matching camera? Will any cheap CCD camera with the IR filter removed work well? I'd kind of like to use a Canon point and shoot, because I can set up CHDK for fixed exposure settings.

Thanks again!

 

[Epsilon]

Then you didn't check out the powerbuck I linked.

More than powerfull enough (9A) for your application. If you want to use 12v input, then take two to drive 3 each.

 

[Tachikoma]

What about direct drive? If one doesn't need dimming and other fancy stuff, is it possible to connect the LED directly to the battery?
For example, I've just ordered this one, would it be advisable to use this to power it? Provided a good heatsink was in place, for how long would it run?

 

[DIWdiver]

No.

On a full charge, that battery would be over 25V, and would surely fry your LED. Read the listing, and believe it. A driver must be used.

 

[ilovewatermelon]

No.

On a full charge, that battery would be over 25V, and would surely fry your LED. Read the listing, and believe it. A driver must be used.

i do agree with the above statement, with a 12V battery that will get charged , you cannot be sure of the exact voltage during float charge , exceeding the recommended voltage will most likely fry your LED at some point , your safest bet is a LED driver

but if your LED is 100W , you can even opt. to use a halogen lamp transformer , as your wattage is quite high.