Pictures posted in Gallery of new DVD burner diode assembly

[buffo]

Ok, I finally got some pictures of this DVD burner module thingy we were talking about earlier. It took me quite a while to take the assembly apart, but I managed to do it without breaking anything. (This, despite the fact that the unit was *really* small!)

Anyway, if you want to have a look, the pictures are in the Gallery right here on PhotonLexicon. If anyone has any input as to how to safely hook these things up and power them, I'm all ears!

I've been told that these units are good for a solid, reliable 90 mw of 650 nm. I'm eager to see that much red! (Right now all I've got is about 14 mw of 632.8 ) While this unit was pretty cheap ($25), I would feel better running it with full optical feedback vs relying on a constant current supply alone. But I can't tell which pin is which on the diode... Anyone else have experience with these?

Adam

[yaddatrance]

Well most single-chip diode drivers which allow 500mA of current
would work for this one... You'll definitely want to cool it in a better
mount as I suspect the diodes are not rated for continuous duty with
heatsinks that small.

[buffo]

Yadda;

Do you have a good source for the purchase of these boards in small quantities? I can't seem to find anyone that will sell them individually.

Adam

[yaddatrance]

When you get a chance, let me know if that's a 3 pin (photofeedback) or 2 pin (current control) diode!

[marconi]

Diodes of this power level usually dont use photocell feedback

DvD drives dont use any optical feedback for power control either..

You will need a CC ( constant current ) power supply.

The control board that comes with DVD drives are useless
and only good for 100ma output..

The beam splitter cubes in this unit are also useless
but the other optics and gratings may be of use.

Also...
Dont expect any kind of lifetime from these diodes in CW use.
Remember, these are pulse type diodes.!!!
There are NOT any that are 650nm for DVD use.
All are 658nm or higher..
When they get warm they fly way up to 670.!!!
Judging from the assembly .. those are only 80mW diodes.
Look-em up!!!

Also, Dont be surprised if it looks just as bright as that 14mW HeNe.

Check out the Technical Discussion part of the forum for some suitable circuits

[Astroguy]

Yadda;

Do you have a good source for the purchase of these boards in small quantities? I can't seem to find anyone that will sell them individually.

Adam

Buffo, I just hooked up my third diode. I got another of the 100 mw units. I again used a leadlight driver board. you have to reverse the voltage for the red diodes compared to the 808nm diodes used in the leadlights. The red diodes in these DVD units have the negative to the case. Mine is outputting 93 mw at 190 ma. It is outputting 658nm the beam is clearly visible outside at night.
Good luck with yours.

[buffo]

When you get a chance, let me know if that's a 3 pin (photofeedback) or 2 pin (current control) diode!

Hey Yadda;

The diodes each have three pins, but in both the high power "write" diode and the lower power "read" diode, one of the pins is NOT connected to anything!

If you look at this picure, you can see the diodes are on the right...

http://photonlexicon.com/gallery/dvd...view_of_diodes

I believe the one on the far right is the "write" diode (notice the heat sink). Both diode have three pins arranged in an "L" shape, like this ":." The upper pin on the left is the one that is not connected, while the bottom two pins are soldered to the ribbon/film circuit traces. (If you look closely you can see the cones of solder holding them.)

I have a couple constant-current circuit plans here that I could use (thanks to the laser faq), but I would also need TTL blanking. My plan was to insert a power mosfet between the output of the current regulator and the diode itself, and apply the blanking signal to the gate of the mosfet. Do you forsee any problem with that?

Adam

[buffo]

Buffo, I just hooked up my third diode.

Astroguy!

Can you post a picture of your diode, and of the heat sink you used? I think the 100 mw units are different from these 90 mw units. (At least, the pictures that littleaglei uses on E-bay are substaintially different for the two auctions....) Do your diodes have 2 pins or 3? (Mine have 3 pins)

I again used a leadlight driver board.

Where are you getting all your leadlight driver boards? I know that Roithner makes a nice one (the EU 38 ), and they're supposed to sell for like $10 each, but I can't find a company that sells them in small lots....

Mine is outputting 93 mw at 190 ma. It is outputting 658nm the beam is clearly visible outside at night.

How long have you operated it at 93 mw? Have you ever run it for - say, an hour or two? For that matter, have you had any of these units die on you yet? (Marconi is correct - they really are designed for pulsed operation, not CW, but I think if we keep them cool enough they ought to be OK...) That's why I'd really like to see your heat sink setup...

Adam

[marconi]

My plan was to insert a power mosfet between the output of the current regulator and the diode itself, and apply the blanking signal to the gate of the mosfet. Do you forsee any problem with that?

Adam

Be very careful with that ...It is very easy to spike the diode doing it that way..
I know..I have a pile of diodes from my early days of trying this..

You will have to dither the input reference with your TTL signal to do it right!!!

Also, Be careful NOT to switch the diode too far below threshold..

I know a lot of companies are getting away with switching
the diode completely off , but it is not recommended.
This will cause the facet of the diode to be damaged.

DPSS lasers are so easy to TTL , but these higher powered reds tend to still emit some light like an LED even below threshold..!!!

Good luck, I hope it works out for you guys

[buffo]

Marconi;

Thanks for the info! If I understand your post correctly, you're saying I should bias the TTL signal such that the mosfet never completely shuts off? As in, keep the current between some low (non-lasing) value and the max of 130 ma, no matter what the TTL signal is?

Gee, sounds like I'd be better off using a power transistor vs a mosfet then...

Adam