** BluRay Diode GB **

[IgorT]

*Edit....I took my blueray module out of the housing and connected it to my bench PS @7.2v, it cleans up the output no end....I was beginning to worry that I had damaged it somehow.....

I just had the same scare with my second diode. But with a bench supply it's ok.

If you're using a bench power supply, that has current limiting, you can limit the current to 45mA (for example, or whatever your current is) and it will automatically drop the voltage enough to achieve this current.

Then, all you need is a capacitor over the diode and you can safely play with it..

Not using a capacitor with this setup can kill the diode tho, due to the voltage spike, before the current limiting jumps into action. I killed two this way.

 

[yes8s]

Something funny has happened to my second diode. It was working normally using a bench supply and LM317 circuit and lasing at about 28-30mA - i was driving it at 40mA with short duty cycles.

I then connected it to a 9V plus LM317 circuit and now it only lases above 38mA and the dot can not be focused as precisely. It's strange - it still works ok but only when i drive it at +45mA

Can anyone explain??

 

[Greyfox]

Something funny has happened to my second diode. It was working normally using a bench supply and LM317 circuit and lasing at about 28-30mA - i was driving it at 40mA with short duty cycles.

I then connected it to a 9V plus LM317 circuit and now it only lases above 38mA and the dot can not be focused as precisely. It's strange - it still works ok but only when i drive it at +45mA

Can anyone explain??

Are you sure it's actually lasing? It sounds to me like what you get when an LD turns into an LED. Sorry.

 

[yes8s]

Are you sure it's actually lasing? It sounds to me like what you get when an LD turns into an LED. Sorry.

I guarantee you it is still lasing...but the lasing threshold has been raised. Like i said it's strange but I guess i'll have to see how long it lasts. I've been running it at 55mA now for two days and it seems fine.

 

[SenKat]

yes8s - I have heard of that happening with the BR diodes....one personactually had his threshold raised up to 150ma !!! Taht was one of the first posts I read about the BR diodes (cannot recall WHERE, now ) and I was designing my circuit based on those statistics....THANK GOD I WAITED !! Whew ! I woulda been SEVERELY pissed off at myself for not reading (and comprehending) the entire write up ! GAH ! Can you imagine ?

 

[disma]

Makes me wonder how long they last in the player, it would suck to get one and have it die that soon... Man they need to make these less sensitive!

Max

 

[rog8811]

I had been wondering how sony set up the drive system on the PS3 to cope with the variation in lasing threshold...I cannot believe there is a geezer sat on the production line, screwdriver and meter in hand waiting to twiddle the pot as the next one comes past.....

Regards rog8811

 

[chimo]

They most likely use Automatic Power Control (APC) via actual optical feedback from the photo diodes versus Automatic Current Control (ACC).

I had been wondering how sony set up the drive system on the PS3 to cope with the variation in lasing threshold...I cannot believe there is a geezer sat on the production line, screwdriver and meter in hand waiting to twiddle the pot as the next one comes past.....

Regards rog8811

 

[rog8811]

Ah yes, I remember seeing that the splitter cubes on the sled deflect a beam to photo diode arrays, I guess that is where it happens.

Regards rog8811

 

[Daedal]

Not particularly... The PD inside the diode is a better option... just connect to that (as does the PS3) and you can limit the output based on the PD output. This can easily be done with some transistors...

--DDL

 

[IgorT]

Not particularly... The PD inside the diode is a better option... just connect to that (as does the PS3) and you can limit the output based on the PD output. This can easily be done with some transistors...

--DDL

If the current regulation would be handled by referencing it to the PD, this would be all the regulation needed, right?


This would be the perfect circuit for the BR. But it would need some safeties. (max current limit to prevent this same regulation from killing the LD in case the efficiency drops too much)

 

[IgorT]

I guarantee you it is still lasing...but the lasing threshold has been raised. Like i said it's strange but I guess i'll have to see how long it lasts. I've been running it at 55mA now for two days and it seems fine.

What happens if you go from the 9V battery back to the lab PSU? Does it return to the old behaviour, or does it stay the same?

 

[Daedal]

[quote author=Daedal link=1189562336/540#553 date=1194463668]Not particularly... The PD inside the diode is a better option... just connect to that (as does the PS3) and you can limit the output based on the PD output. This can easily be done with some transistors...

--DDL

If the current regulation would be handled by referencing it to the PD, this would be all the regulation needed, right?


This would be the perfect circuit for the BR. But it would need some safeties. (max current limit to prevent this same regulation from killing the LD in case the efficiency drops too much)[/quote]

Igor, Photo Diodes work by generating some current based on the light incident on them... it's like a photocell. The feedback (this current generated) would be based on the light output of the LD itself... and thus no calibration would be needed aside from actually setting the amount of current pass based on the PD feedback... There is no better calibration method that I am aware of...

--DDL

 

[LarryQ]

AHHHH...I just learned something!!!

I wasn't aware that the PD actually generated a small current...I thought a voltage was passed through and the resistance to that current is where the feedback came from!!

See you learn something new every single day!!!

Thanks Dae!!!

Larry

 

[Daedal]

If you look at the EXCELLENT Repair FAQ website by Sam Goldwasser you'll find a neat typical response curve for photocells and photo diodes to specific wavelengths of light of equal power...

Also, the other great site by Leslie Wright along with Sam shows the current feedback form the different diodes when run at 5mA

It seems that at 5mW of 405nm the current going out of the PD is 115uA ;D

Good luck working with that...

--DDL

 

[scopeguy20]

Wow Mo! This inf on Sam,s FAQ really helps my wonderment. I thought my 11 mW greenie (as measured by my LPM for 632.8 nm from Metrologic), was more like 15 mW, and using the conversion on his page it works out! I knew some of the stuff on Sam's FAQ, but had not seen this part! Thanks for pointing that inf. out!
;D ;D ;D