Two 20mw 635 diodes; 9mw total output

[LtKernelPanic]

Ok I'm annoyed here. I've purchased two 20mw 635nm diodes and between the two of them I've managed to get a total of 9me out of them. According to the data sheet at 70ma I should be getting 20ma. My latest diode from modwerx maxes at 4-5mw. I'm finding it hard to believe that I got two bad diodes (one from DJNY's GB and one from modwerx) so it must be something with my DIY driver.

Here's a diagram of the driver I built and a photo of the completed driver with the first diode.

http://laserpointerforums.com/attac...-went-wrong-20mw-635nm-ld-only-5mw-driver.jpg

the connection from batt+ to LD+ is via the host.



2011-07-09_11-05-21pm by ltkernelpanic, on Flickr

I did notice one thing when hooked up the diode. looking at the data sheet

http://modwerx.com/635nm_20mw_laser_diode.pdf

it shows the case pin (2) should be LD+ and pin 1 should be LD- however it turned that pin 3 was LD-. Am I reading this wrong or is the data sheet wrong for the diode I have?

I'm at a loss here as to what's happening. I can think of a couple scenarios with the most likely being is my driver is somehow damaging the diode but testing it on my test load shows a steady output of ~71ma (I forget the exact number). I'm curious has anyone bought one of these diodes and actually gotten 20mw out of one?

 

[lazeerer]

Low Power diodes are extremely sensitive to Heat.

I cant remember the exact mA of my 20mW one that i got from Modwerx but i know it was above 70mA.

Ill take mine apart for you to check. Hold Up.

 

[DTR]

What lens are you using?

 

[lazeerer]

Mine is running at 86mA.

Iam Using the AR coated Acrylic lens.

How many diodes did you use on your test load.?

Whats your Voltage in.?

Why do you have a diode on the driver.?

Like i said my Low power 635nm diodes are sensitive to heat. Not in a sense of soldering but claimant.

When iam using my 20mW after warmed up it does 18mW. When fully cool it will do 21mW-22mW.

635nm seems to like to run really cool...

 

[LtKernelPanic]

Lazeerer-

I tried upping the juice to about 83ma (15ohms on the 317) on my original diode and other than the output shifting towards 650nm it stayed at 5-7mw which made me think maybe I got a zombie and is why I got another diode.

DTR-

Just the standard acrylic. Would that kill it that much? I could use the glass AR cloated lens from my LPC build if that's help.


I'm about >< close to calling a code F and buying one of those 20mw 635s in the jetlaser GB.

edit:

to answer lazeerer's questions:

1. I used either 3 or 4. I can't remember to be honest.

2. Vin to the driver is ~12v last I checked. it's 3x10440 LiIons.

3. The Diode is there to keep me from frying the diode if I put the battery holder in backwards since this is my only case positive build other than my other 635 pen. Could that be messing with the regulator? I suppose I could whip up another driver on my breadboard and test the other LD without the diode.

Like I said in my first thread on this topic a month or so ago I did several tests with some being days apart. All were done in a room where the ambient temp was about 75F. Even on the first test they metered low. I think I'm just jinxed with 635 diodes (3 met their demise in my 5mw pen build).

 

[lazeerer]

Dont Jump the gun Yet.

I was too disappointed with the first 20mW i got second hand. It was doing the same thing you are saying.

If you want send them over to me and Ill let you know for sure if you killed them. If not ill send the back Running or dead as they came. I can Hook the up to Aixiz Drivers for you Just cover cost and shipping. PM Me.

Also Know that Lower power 635nm and 685nm diodes do not like Many Drivers.

I use the Aixiz Red Driver as that works the best IMO.

What LPM are you using.? This can be a big factor too.

 

[LtKernelPanic]

Thanks I may certainly take you up on that offer. The first readings I took on diode #1 were on my Radiant Alpha LPM. I confirmed them after I got my USB LaserBee. All the readings for #2 were on the LaserBee. For the hell of it I'll grab the lens from my LPC and try it.

 

[Cam453]

Are the modwerx 635's case positive or negative? I'm planning a build with this diode and it seems for 7mw if it were case positive it wouldn't be worth the hassle.

Edit: sorry my bad I noticed the way it received the battery + through the host

 

[lazeerer]

Are the modwerx 635's case positive or negative? I'm planning a build with this diode and it seems for 7mw if it were case positive it wouldn't be worth the hassle.

Edit: sorry my bad I noticed the way it received the battery + through the host

No Modwerx sells Good stuff. If he says they are 20mW they are 20mW.

I can Confirm this 2x. Both Mine did 21mW. Look Up his thread he posted about them. You will see my post there.

Or

Just go Here:

http://laserpointerforums.com/f58/20mw-635nm-diodes-17-20-a-63625.html

You will find my post on the second Page.

 

[LtKernelPanic]

They are case positive and as Lazeerer said Andrew over at modwerx sells good stuff. The problem I'm having is either in my driver design or I need to push it a bit more.

 

[lazeerer]

You will know if you LED the diode. The dot will Look really weird.

 

[Cam453]

Has anyone been able to power these off of one li-ion. I've seen one build but it uses the driver from a dead green module. I was wondering whether a LDO regulator would be able to handle the voltage seeing as the diode requires 2.3v. With a charged cell shouldn't that leave 4.2v-1.25v-2.3v=0.7v of runtime?

 

[LtKernelPanic]

You likely could if you use a regulator with a low LDO. I think the LM1117's is ~1.2v so you could use that. With a diode that draws <100ma you'd probably get a semi-decent run time between charges. If your host can take a 18650 you can use 2xRCR-123s instead and not have to worry about short run times or having to use an LDO regulator. That's one reason I went with 3x10440s in a couple of my builds.

Also if you LED a diode it's pretty obvious. I have a 5mw 635 that I LED'd and I could instantly tell when it happened.

 

[Cyparagon]

1.2 plus the Vref of 1.25. 1.2 is only applicable if you use it as a voltage regulator.

 

[Cam453]

That's what I thought Cyparagon. I guess it's two 10440's in a pen host for me.

 

[aidacity154]

Hey all, I am using a 25 ohm rheostat potentiometer, and turned it up slowly and the diode is outputting a very bright light, i am not sure what current i am at, but i am sure that it is putting out a light equivalent to 20-25 milliwatts.

EDIT: If you guys want to see a picture of my setup i can post one.