20w diode bar driver help

brentschulze · Sep 23, 2012

I need t know what I can do to get a driver for an 808nm 20w bar diode

I'd also like some thoughts on a power source hi capacity li po battery or li ion packs etc...

ARG · Sep 23, 2012

You're trying to make a handheld out of it? What purpose would a 20W IR handheld serve?

You're going to need a fairly large driver capable of handling 20A. It would be best just to make a linear driver yourself.

Wolfman29 · Sep 23, 2012

Ehhh... linear driver wouldn't be that bright of an idea. Maybe it would be a good idea if you could first get several li-ions, buck down to say 2.5V and then make a linear driver.

Blord · Sep 23, 2012

I think he want to make a portable IR flood light for night vision. The power source depends how long you want to use it mobile. For the whole night you will need something like a car battery.

Cyparagon · Sep 23, 2012

Application? Design constraints? Budget? You're giving us two spark plugs and a crank shaft and asking us to build a car.

Wolfman29 said:
Ehhh... linear driver wouldn't be that bright of an idea. Maybe it would be a good idea if you could first get several li-ions, buck down to say 2.5V and then make a linear driver.

If you're going to buck anyway, why not make a buck driver?

Fiddy · Sep 23, 2012

You have to ask yourself 1 question....

brentschulze · Sep 23, 2012

Thanks for all the responses,

2 separate designs actually, and yes one is an ir flood for night vision.

2nd design is prototype for cutting on a cnc just not sure wattage needed for various materials.

Weight of battery's not a big issue just not using a car battery.

Drivers...I'm fairly new so don't know much about driver designs else I wouldn't be here asking....or buck terminology...also don't care if needing to stack drivers to accomplish task....

Cyparagon · Sep 23, 2012

Don't waste your time with diode bars for cutting or CNC work. The spot is too large.

How did you choose 20W for night vision? Night vision is sensitive to light by definition, so you don't need that much. And why laser? LEDs are cheaper, easier to drive, safer, and more robust.

brentschulze · Sep 23, 2012

I got a good deal on the diode bar that's why. I was going to make a focus assembly to project the beam for night vision, and on the other a fine focus assembly to dial the beam to a point.

Last I checked when looking around couldn't find any "round" 20w-150w diodes just bars so I got the 20w for under $40 now I just have to find a way to run it is all

Cyparagon · Sep 24, 2012

The story thus far:

"Hey guys, I found this lawn mower for sale. It was only $5. Now how do I cut my hair with it?"

brentschulze · Sep 24, 2012

I thought this was where I was supposed to come for help, instead I get ridiculed. Nice to know. Now if I found a lawn mower and was going to use it for hair cutting...

Disassemble motor from deck, remove blade, attach gear reduction motor, attach flex drive shaft hose assembly, attach horizontal bar with cam assembly, attach hair - razor - reaper head with safety guide, cut hair outside, check oil every 30-50 haircuts. I can make unhelpful comments too.

Now back to question at hand and let's focus on the question, driver for a 20w laser diode bar!

Hiemal · Sep 24, 2012

To drive that big of a diode bar, I would probably go a linear route as well to be honest.

With SMPS based drivers you have to deal with current limits, and excessive heat production. If you use a large linear driver, bypassed with a transistor (something like this; http://i.imgur.com/YlPp8.png ) Then you can just heatsink the hell out of it and not worry about current limitations. Plus linear drivers are noise free, and extremely robust in comparison to any switching power supply. Not to mention, if you keep the input voltage extremely close to the output voltage (which will be around 2.2 volts I'd imagine) then the linear driver won't even be dissipating too much heat.

Wolfman29 · Sep 24, 2012

Quack - that's almost my idea. Except, if you wanted to use batteries, there is no chance in hell you are going to effectively draw ~20A from li-ions. That's why I proposed bucking first. Buck from ~12V to 2.5V with a high-power, CV bucking source THEN add a linear supply afterwards.

Also - care to explain how that circuit that you recommended works over PM or something? I have a project similar to this and if I could use a linear power supply that I come home-brew that wouldn't kill too much heat I wouldn't complain!

Flaminpyro · Sep 24, 2012

This is a place to come for help so please don't judge all the members here by what one ****** bag says, some people just get off by busting others balls for no reason at all !

As for your 20W LD I think it's going to require more than 20 amps if you plan on running it at full power or even close to that.

Maybe you can get all the down field illumination you need for NVG at 10 amps or less ?

So you are going to probably have to build a driver for it unless you plan on buying an expensive off the shelf model.

How about a very large wire wound power resistor, something like these> Power Resistor 100Watt choose a 1, 2 or 3 Ohm | eBay

This looks like it could work for you> Power Resistor 300Watt Choose a resistance value | eBay

for portable power maybe one of these will work > http://www.lithiumion-batteries.com/lithium-rv-deep-cycle.php

Good luck and let us know how it goes

brentschulze said:
I thought this was where I was supposed to come for help, instead I get ridiculed. Nice to know. Now if I found a lawn mower and was going to use it for hair cutting...

Disassemble motor from deck, remove blade, attach gear reduction motor, attach flex drive shaft hose assembly, attach horizontal bar with cam assembly, attach hair - razor - reaper head with safety guide, cut hair outside, check oil every 30-50 haircuts. I can make unhelpful comments too.

Now back to question at hand and let's focus on the question, driver for a 20w laser diode bar!

Cyparagon · Sep 25, 2012

OP: What's the best way to swing sledge hammer?
Cyp: Why do you need to swing a sledge hammer?
OP: To open this can of beans.
Cyp: A sledge hammer is NOT a good tool for opening beans. You want a can opener instead.
OP: But I found a cheap sledge hammer. Why are you ridiculing me?
FP: Ignore Cyp, he's being a douche bag. The best way to swing a sledgehammer is...

billg519 · Sep 25, 2012

If you really need to power this from batteries, lipos can deliver huge currents. These are the batteries used in RC cars and planes. They will provide the current, but the run time would not be long per battery. I have a 4.2V lipo that can provide over 100A, but only for about 5 minutes ... A linear driver as shown above, or some nichrome resistance wire, will be good enough for an IR illuminator. This 808nm bar won't cut many light colored materials and would be frustrating for CNC. A CO2 tube from ebay would be better for the CNC.

20w diode bar driver help

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