Need tips on NOT killing LDs

[somail]

I have tried twice to harvest a LD from a 20x Sony burner. Once connected to my driver, both diodes basically look like very bright red LEDs. Before buying any more drives, I am trying to figure out what it is I am doing that could cause the deaths.

I have two theories:

(1) I have the basic DDL setup with the exception of the 1N4001 diode, as my local shops seem to be out of them. After the 3v drop thorugh the Lm317, my MM says I am still sending close to 4v-4.2v to my LD. Could this be killing them. I have read alot of threads about too much current killing diodes through heat, but voltage seems to be of little concern. (Of course most people are probably not running more than 3v-3.3v with a 1N4001 in the circuit.) I guess I could remedy this by putting a low ohm resistor before the Vin pin on the Lm317.

(2) The photo and Gnd pins on my diodes have all been soldered together. Both times, I have tried to desolder this connection, and I fear the heat is killing the diode. I just read a thread that says it is okay for the two to be connected. Is this true? Have I been wasting my time and killing my LDs doing this.

I know its a pretty open ended question, but would one of these two faults cause a bright LED type failure. On both LD, current never exceeded 200mA (per my MM)

Thanks for any insight.

 

[drlava]

1) - test your driver with a load before connecting the diode
- only connect the diode with the circuit powered off and discharged NEVER connect it or disconnect it with power on.

2) yep that's fine there's actually no monitor photodiode.

3) heatink the diode.. heat kills!

 

[somail]

Thanks for the reply. I have done some load testing, with a few LED's in series. I know its not the same as 4 x 1N4001's (which everyone seems to use) but it does still give me a load.

Do you guys find this to be a typical type faliure (i.e. bright LED type light being emitted from the LD)? It seems like most threads about deaths mention a low amount of light, or almost nothing at all being emitted after death.

 

[Razako]

You might be killing them with static. Also DO NOT power up the driver and hook the diode up without discharging the capacitor. Doing so will instantly kill your diode.

 

[drlava]

the diodes always look like bright LEDs until you collimate them. you ARE trying to collimate them right?

 

[somail]

Thanks.

I have been trying to be carefull with the static.  I have been wearing a strap and have been carefull to always be connected to a ground.  I have been discharging the cap after everyuse, but not the LM317.  I don't know the inner workings of the LM317 that well, but the schematic does show a few caps in it.  But I would think that any juice left in the LM317 would just get passed to the cap and the LD. Especially since I usually cut the voltage source first.

Anyways, if I was to put money on it I would guess its a heat issue with the desoldering between the photo and Gnd pins.  Lets just say that my heat sink usage is next to zero, nada, or ziltch.  In fact the first time, I desoldered and then soldered on pins without the diode being connected to a module or any type of rudementary sinking

@Drlava ------ Is it a big read flag if I have no idea what you are talking about or what that entails?? I am assuming some type of focusing?? I am off to frantically click on the search button.

 

[Glaserfan]

If you light up the diode without a lens in front of it, it actually looks like a bright LED. If this is what you are seeing, and it in fact STAYS bright, not just a quick flash, your diode is still good, you just need to attach the lens and focus it. Of course this is assuming you have it in a module......NEVER light up a diode, or do too much if any soldering without the diode in a module.

 

[somail]

Ya, I'm an idiot. Now I understand why EVERYONE uses the aixiz modules. I actually have one of my diodes in a module from a cheap laser pointer, and when turned on it basically emits a large red circle through the end of the module. It never even occurred to me that I should put the lense back in the module to focus the light. It makes perfect sense because when shined on the wall it looks like an 8 inch diameter laser beam.

Since I am not going to be using the aixiz module that everyone else uses, are there any tricks or ideal distances between the plastic lense and the diode. I am guessing its just a trial and error thing.

It is funny to me that I was able to do the most difficult part of this project with ease, but yet screw-up the most basic portion. :

 

[drlava]

It's a happy ending after all  the collimator lens should be at the distance that produces a straight beam (where the focal point of the lens is at the laser diode emitter).  Too close and the beam will spread, too far and the beam will cross at a focal point and then spread.  You'll get the hang of it!

 

[pwnstar]

what are you going to use instead of a aixiz housing?

 

[sk8er4514]

you should really just use an aixiz laser module housing. they're really cheap and get the job done wonderfully.

 

[somail]

@ pwnstar & sk8er4514

Originally I was just going to use one of the other modules I had from some cheap pointers that I had disected. I tried for a while last night to get the focusing correct, and it really wasn't coming out the way I had hoped. I went ahead and ordered two aixiz modules since I would rather spend $14 then waste 3 hours of my time, which I consider to be at least worth $15 .

 

[pwnstar]

@ pwnstar & sk8er4514

Originally I was just going to use one of the other modules I had from some cheap pointers that I had disected.  I tried for a while last night to get the focusing correct, and it really wasn't coming out the way I had hoped.  I went ahead and ordered two aixiz modules since I would rather spend $14 then waste 3 hours of my time, which I consider to be at least worth $15   .

lol yea, I think thats the way to go. Aixiz moduals have better heat sinking, than whatever you might find in a cheap pointer.

 

[Zom-B]

I'm not so sure. I have some very old laser pointers of $10 and they have a massive brass part of 1/2" diameter and by 1/4 inch length with the collimator protruding from it. It has proven adequate heatsinking for a 270mW red DVD for a duty cycle of 5 minutes, and indefinite time at 200mW.

 

[pwnstar]

Well when I said cheap, I ment like a small dealextreme red pointer.
that looks like a good houseing for a red right der^^^

 

[pwnstar]

my definition of a "Cheap Red Pointer"

lol