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Hello from Ohio, from me and my burnt diodes

zowen22

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Hello,

I want to understand and build a few of my own lasers, and had a few basic questions.

How do you find a driver that will be compatible with a diode, is it just making sure the driver output matches the diode input?

How do you measure the output of your driver, to make sure you’re not overcooking your diode?

What’s the difference between the bare and open diodes, versus the ones with the little metal cap?

Merry Christmas:)
 



Lifetime17

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Hi, The way it looks from here is that this is your 1ST post.
Did you do an intro in the welcome section first??
tell us a little about yourself , Your interests , accomplishments
Rich:)
 

Alaskan

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Hello fellow Buckeye, welcome to the forum. I'm originally from the Akron area.
 

paul1598419

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Welcome to the LPF. You have more questions than I have time to answer them. I could spend at least an hour on the one ones you have articulated here. Merry Christmas to you.
 

zowen22

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Thanks for the replies:) I actually attended the University of Akron. Still just looking for a grasp on the driver versus diode pairings.
 

hakzaw1

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Hello fellow Buckeye, welcome to the forum. I'm originally from the Akron area.
WHAT?? Akron!!! never knew that I lived in Kent before moving here- & before that in Canton!!-

where in Ohio are you (the OP)?

Thanks for the replies:) I actually attended the University of Akron. Still just looking for a grasp on the driver versus diode pairings.

When a new member seems to only wants something
it makes me sad-- Some call them--'Hit and run'
You have a lot to learn == so please stick around-
'we always need new members-- especially buckeyes
We all have killed diodes== part of thelearning process
 
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Alaskan

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Tell us which diode you want to use and how close to full output power you want to run it at and I am sure you will be given a driver commendation.

If you are building a laser pointer out of those open can Mitsubishi LPC-840 650nm red laser diodes I've seen more than one report of the diode burning out when run at the CW rating of the device. I'm not sure what the problem is, but when I first started in this hobby I also had one burn out when producing what I thought was 350 mw of power. Perhaps I just didn't have it heat sinked well enough, or lacking a laser power meter was really pushing it far too hard, had the driver maladjusted or something else wrong, I don't know. Maybe you are doing so too? One thing I learned quickly is never to have the diode hooked up to a DC power supply while turning it either on or off (I'm not meaning a laser diode driver, I'm referring to a lab style or other DC supply) regardless if using a constant current power supply or not because the voltage control is momentarily lost while turning it on and perhaps also while turning it off, destroying the diode. For more information about how to set up a laser diode driver, see: https://sites.google.com/site/dtrslasershop/home/laser-drivers
Mitsubishi LPC-840 Specs:

Made in: Japan
Power output: CW 350mW
Pulse Power: 450mW
Working Current: <340mA .....(Is this for pulsed power or CW? If max pulsed current then for CW the max current will be less)
Working Voltage:2.2-3.0V


To chose a driver you first need to know the full forward voltage (operating) of the laser diode you want to use with it, the driver output voltage must be able to either adjust low enough, or high enough to match what the laser diode runs at. Next the driver needs to be able to handle the current required for the diode, so you need to know the full current rating of the laser diode. Although I mentioned the voltage the diode needs to run at, the other important control a laser diode driver does is to the keep the current constant because otherwise without that control as laser diodes heat, they tend of pull more and more current until the device overheats and is destroyed.

Laser diode drivers are made so the current can be set to a specific amount and stay there, so if the diode gets hot and begins to pull more current, the voltage is automatically reduced to keep the current stable or the same, if it cools down the voltage is then increased enough to keep the current from dropping too, it's a feedback loop referenced to current (actually, measuring the voltage drop across a precision resistor caused by the amount of current flowing through the diode) but what is happening is the voltage to the diode is being increased or decreased to keep the current the same.

Open Can:

Some of the red laser diodes are open can, apparently they can run without degradation when exposed to air, but they should be inside some kind of sealed container so dust or dirt cannot get on the diode facet where it can burn the contaminate onto the micron sized optical surface of the diode substrate and destroy it. Other diodes such as the NUBM07E which is a high power ~465+ nm blue laser diode will degrade and fail early when exposed to the air, even if protected inside a laser diode mount and lens holder assembly as it isn't sealed from the air.

I mention the 07E diode because it comes with a gball lens crimped into it's cap which are often slightly out of full collimation, so we often remove the can and gball replacing it with an adjustable focus lens assembly, but then when the diode is no longer sealed and exposed to air the life is substantially reduced. I've never seen anything definitive regarding which diodes are OK to expose to air while operating and which are not, I'm speaking from my own direct experience and reports I've seen here from others. Because of this, except for some red wavelengths, it appears best to leave the can or covering over the diode elements intact.

Chris - Hak, I'm actually from Wadsworth, Ohio but hardly anyone knows where that is, I know Canton though.
 
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hakzaw1

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to the OP
Alaskian has given you great help---plase show appreciation by making a nice intro placed in the newcomers section. Know that we have your back-- this is not a forum where you need to keep everything private.
Especially true when using PM -- only person who sees is the one you conract.

My bucket list includes the meets in the NW-- way too much good stuff goes on than I can list.
I ESPECIALLY like to be around so many lasers/laser folk and yet nobody asks WHY? we know the answer.
IF you can only make one LEM--go to SELEM in mid august. It has grown to almost 5 full days of events. I have never regretted the long drive to Newton NC--made 5 of them in a row!!
Many like the BS&T area--we put our name and price and those wanting come and finish the deal. (no need to sit on your stuff) ----its laid back and awesome !!

You can PM me if you need more SELEM info ( South Eastern Laser enthausists meet) many have already paid and have plans both ride and lodging sharing helps keep the cost down.. I lucked out 3 events winning super door prizes worth >$500.

hope to see you there--Len
 

Alaskan

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He’s too busy with his Christmas toys to come back and check the forum ;)
 

zowen22

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Wow, thanks a ton guys, and Alaskan, that's a ton of info, thanks. I'll make a post in the welcome section, I plan on sticking around
 




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