Dr's Diodes :-)

Hemlock Mike

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I got some time to test Dr_Lava's kits tonight. !!!

I'm not using the 2.7 Ohm resistor but rather an LM317 current source and carefully monitoring the current. The capacitor is installed just incase there is a glitch in the power.

My power meter maxes out at 40 mW and I havent had time to recalibrate my beam splitter but here's what I have so far.

mA mW
80 6
100 21
120 34
130 40+ Overrange You do the math !!!

I've gone up to 310 mA and it runs cool but BRIGHT - I am using goggles !!

I focused it at 18" and it cuts black paper, lights matches etc. It's easy to focus it at 4' to do the same !! (Use teflon tape to tighten the threads on the focus ring - easy to change ! )

At 300 mA I read a junction voltage of 2.75.

I'm going to bed before I screw it all up - I want to sleep happy !!

Thanks Dr ------------

Mike

I forgot the zero on the current readings - Big OOPS !!
 
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liveforphysics

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Feeling a bit foolish, I actually ran one directly from a 3.6v LiPoly batter cell... It got warm pretty quickly, the beam was very good, and I was lucky enough to have appearently not damaged the diode. I should add that the battery had been needing to be re-charged before I tried this, so its possible cell voltage was in the low 3's area.

I have been really pleased and impressed with the diodes from Dr. Lava.

Thanks!
 

dr_lava

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Well, the lasing threshold according to the data sheet is 60mA, so I'm guessing Hemlock Mike's mA numbers should be multiplied by 10 to make sense. I PMed him about this earlier, but no resp. yet.
 

Hemlock Mike

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I realized this while at work this AM. I've changed it.

One of those late night things ......... The good Dr figured it right.

Mike
 

Hemlock Mike

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I've turned mine up gently to 320 mA so far. I don't know if I get enough more output to warrant that current but Dr_Lava reports a brief run to 400 mA.

I can pop balloons etc with 300 ma easily when focused. You go over Oh say 270 mA and you are kinda on your own -- new territory -- :)

Please report your findings -- Others will be doing so as testing begins.

Mike
 

Hemlock Mike

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I popped a balloon tonight at 210 mA at 4' with the "kit".
It was a black orb and went easily. Focus is the key here.

Mike
 
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dr_lava

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Yeah the focus on the kits is pretty nice. I was melting the plastic back of my black chair at 15' without knowing it the other day. 300mA. Oops! At that distance the atmospheric effects from my radiator were making the beam jiggle a bit.

I have tried modulating one at 3MHz with a simple pnp circuit, but the apparent brightness didn't increase as long as the average current stayed the same. That answers one question someone asked in the GB thread. It is possible that the diodes can be driven harder if modulated this way, according to the data sheet. Haven't tried that yet.


Mike, try carefully opening the aperture on the back of the lens and see if it increases the power output in the beam.. It increases scatter a bit, but I think it can increase beam power too.
 

stevetexas

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If anyone has any of these left I'd love to buy one or two... Geez, you guys are having all the fun.:awman:
 

kf4zht

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COMMANDR said:
Newegg has a passive cpu cooler on clearance for $42.00, maybe could be modded for pushing laser diode performance.

just a thought

Gary
http://www.newegg.com/Product/Product.asp?Item=N82E16835109132

http://www.newegg.com/Product/Product.asp?Item=N82E16835118223

Still waiting on my diodes, but I was thinking of putting the diode in a solid piece of AL with a hole drilled into it, that on the cold side of a peltier, and then the biggest heatsink I have (think it is from an athlonxp) with a 120mm 120v fan cooling it. How does everyone think that will work?
 

dr_lava

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Like mike said, the power gains reduce above about 250mA, it's probably not worth it pushing above 300mA. Sub-ambient cooling can increase the output, but it also increses the diode's resistance, meaning you'll be dumping more power into the diode for the same given current.
I'd say $45 for a heatsink designed for a thermal dissipation of 100W for a $12 kit that dissipates 1W is a bit overkill, but whatever makes you happy :)
 

kf4zht

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Yeah, everything that I need for mine is laying around my workbench. I dont even have to get out of my chair to grab it.

I figured I would have to set one up for major overkill cooling. Just for kicks.
 

Hemlock Mike

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I already did open the plastic aperture a bunch. I havent tried measuring the power accurately yet but it did seem to help the output and like you say - a bit more scatter. I even blew the little cruds out of the lens holder but again I doubt if there was much gain.

Took about 6 seconds to burn through a black plastic box last night - 290 mA.

Mike
 

Hemlock Mike

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I see many parcels being delivered today. This is good stuff but watch out for static AND use a GOOD CLEAN power source. If you don't know what you have - use cells - follow the instructions. Keep the current down until you have good control. 150 to 200 mA will burn stuff. Protect your eyes.
I am pleased with my kits and have only tried one.

Mike
 

dr_lava

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Here's a plot of the output power with the opened aperture. Laser was kept at room temperature (21 degrees) with a heatsink setup posted in the main thread. Power readings were made using a calibrated power meter.

Note that according to the spec sheet it is not reccommended to take the current level above 200mA, But I did in this case to complete the plot so you wouldn't have to. Diode lifetime is probably degraded above a certain current level, as yet unknown what that is exactly, and it probably varies a bit diode to diode.


powerplot.jpg
 

COMMANDR

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Got my kits today!!! Now the fun starts. Did not realize the diodes were so small. Very happy with the kits. Thankx again dr_lava for all your efforts.

Gary
 

Hemlock Mike

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Neat observation --- The case assembly measures about 0.470" and so does the assembly from an old leadlight !! This could make a nice looking pointer with focus. I was smoking black paper at 15' last night.


Mike
 

Rando

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I've got one running out of an old Garrity flashlight. It's a little rough right now but she's throwing a bright ole' red dot around! Powering from cr123.
 

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