Driver Question about 300mw 808nm diode

I've just purchased 5 of these:
808nm 300mW High Power Burning Infrared Laser Diode Lab - eBay (item 320635286222 end time Jan-25-11 20:46:06 PST)

I have a bunch of lasers that I busted the diodes in, and I would like to get them up and running again as a little DIY project to help me play around with cheaper mistakes before I make costly ones ;-)

The 808nm diodes are for some greenies. I already have the appropriate crystals, lenses, hosts... But the question then comes into Driver/Diode.

I would like to purchase some drivers instead of using the existing ones I have because the ones I have... I don't trust exactly. I mean, they used to work on different diodes, but I couldn't tell if they were 200mw 808nm diodes or 300mw 808nm diodes. I'm willing to bet 200 but I don't know.

ANYWAY, to get to my question:

I'm looking for a driver that will do what I need it to, to drive the 300mw diode. I don't see a spec sheet that would show the relationship between the mA the diode needs vs. the voltage. I'm still a newbie to things like Ohm's law *though I've been trying to "get it"* so I'm having a hard time figuring out the real-life application. I can do the math part, but it's figuring out HOW to make it apply that I'm struggling with. Which is why I wanted to get into this project.

I guess that wasn't really a question so much as a statement... So let me see if I can compile my thoughts here into concise questions:

1 - I know that the diode takes 2.2 volts according to the auction. How do I know what the mA should be? Isn't the mA calculated based off of the Volts/Resistance? How would I measure/tell that?

2 - Why do some drivers talk about how many mA's it can provide? Isn't this technically the draw from the diode that would determine this? Or is this the driver showing what it'll provide, but shows the equalavalent power source needed to provide that current?

3 - I was looking at this:
2pcs constant current laser diode driver 80-500mA w/TTL - eBay (item 360334185097 end time Jan-13-11 18:24:41 PST)

Suspecting that it's variable output based on power source, wouldn't this suffice as an appropriate driver for a 300mw 808nm diode?

I'm still a little lost in the electrical side of things... fully seeing how to APPLY the practical knowledge I've learned recently.

Any hints, tips, suggestions or ideas would be GREATLY appreciated. I'm somewhat lost. What I CAN say I've learned is that when you remove resistance on the driver, the diode gets brighter. Until it pops. lol

(Which is why I would rather understand how much brighter, why, and until what point instead of just blowing up diodes)

I redt somewhere that it takes 400mA current to provide 300mW ir power.

2 - Why do some drivers talk about how many mA's it can provide? Isn't this technically the draw from the diode that would determine this? Or is this the driver showing what it'll provide, but shows the equalavalent power source needed to provide that current?

Click to expand...

I'm not very deeply into eletronics, so here's my laymans explanation:
The laser diodes presents to the driver a certain "forward voltage" or voltage drop.
Below that specific "Vf" voltage, the diode's resistance is very high, allowing for only a very small current
to flow. At and above "Vf", the diode's resistance suddenly drops to a very small value -> current flows easily across the diode.
It then proceeds to gobble up any current that it can get, if it gets too much though -> POOF!
So that's why it's so important that we use CONSTANT CURRENT powers sources
to driver our diodes. The (well tuned and properly set up) driver won't let the diode
draw more current than is good for it's health.

anselm said:

I'm not very deeply into eletronics, so here's my laymans explanation:
The laser diodes presents to the driver a certain "forward voltage" or voltage drop.
Below that specific "Vf" voltage, the diode's resistance is very high, allowing for only a very small current
to flow. At and above "Vf", the diode's resistance suddenly drops to a very small value -> current flows easily across the diode.
It then proceeds to gobble up any current that it can get, if it gets too much though -> POOF!
So that's why it's so important that we use CONSTANT CURRENT powers sources
to driver our diodes. The (well tuned and properly set up) driver won't let the diode
draw more current than is good for it's health.

Click to expand...

OMG - That is a lightbulb moment. That COMPLETELY makes sense. It's a diode, which has a voltage threshold... As soon as the initial resistance is overcome, the floodgates open and resistance drops to almost nothing, but then there's an output of frequency. The more voltage you pump into it, the higher the output until the medium can't handle it anymore. (I think I'm right in explaining it back that way)

Sweet. That part makes sense... Let me see if I can figure out the rest. Hopefully other people can contribute some more "layman's" explanations because those metaphors seem to help

"You must spread some Reputation around before giving it to anselm again."


damn.


ontopic: well you could try applying the 20% DPSS efficiency law on the diodes
if you own a 50mW green module, thats pretty sure that it used a 300mW diode (or if you bought from china market, a 200mW overdrived diode).

The more voltage you pump into it, the higher the output until the medium can't handle it anymore. (I think I'm right in explaining it back that way)

Click to expand...

Again, I don't know much about these things, but I think with laser diodes it's more about
current than it's about voltage.

anselm said:

Again, I don't know much about these things, but I think with laser diodes it's more about
current than it's about voltage.

Click to expand...

I think you're right, but what I CAN say is that current and voltage are directly related. V=IR (Voltage = Current x Resistance)

(Yes, I just started learning Ohm's law lol)

Anyway - I'm still trying to learn HOW these apply in a practical sense... but I'm slowly picking it up anyway