Has anyone used these LDs? Also, noob questions.

[gusgus]

Hello all, first post. Great forum!

I've been saving old CD and DVD drives for laser projects for a few years and am ready to start. I ordered a few LM317s and some 555 timers to make some simple pulsed current sources to power the diodes. The main problem is that I don't know much about the LDs themselves, so I figured I'd post them here to see if anyone has data on them, or any pointers for their use, no pun intended . I also have a few questions at the end. Thanks in advance!

Drive 1: Sony CDU611 24x CD drive (Sept 1997)
Known ratings: nothing.


Drive 2: Samsung SD-608 DVD/CD drive (Nov 1999)
Known ratings: lifetime: 125,000 hours at 25% duty, 5-45 deg. C ambient temp, DVD:650+/-10nm 7mW max, CD: 785-5nm/+15nm 10mW max.

Drive 3: LG CRD-8322B CD drive (Jan 1999)
Known ratings: lifetime: 125,000 hours at 10% duty.

Questions:
1) On most of them I was able to find expected lifetime of the drive, usually 125,000 hours with a specified duty cycle, e.g. 25% duty. Does this imply that the laser is being driven at 25% duty?

2) On the one that I found the above duty data as well as a power rating for the diode, do you think the rating is stated for CW or the % duty mentioned in question 1?

3) On these drives, are the lasers generally driven at +5V, +12V, or some other voltage?

4) For CD/DVD reader combo drives, is there a single diode with two modes of operation, or are there two separate diodes (one for CD, one for DVD) nested within the single LD package?

5) For the two unknown laser powers, what do you think is a safe power level that I should try first so they don't burn out? Is there a methodical experimental method that I could employ, such as gradually increasing the power, that would let me determine what the best power is for these LDs?

Thanks again!

 

[bobhaha]

1) No, this refers to the PWM duty cycle some info can be found here.... >>Click me<<
2)There is no way to tell, but I would guess its stated at PWM duty cycle power, because of it very low power and a duty was given.
3)Laser are not driven by voltage. They need a constant current driver, to prevent spikes preventing the diode from dieing. These constant current devices are referred to as drivers. The diode will draw its own voltage, but will need a stable and constant current source. Search, flexdrive, LM317, microboost, rckstr drivers.
4)There are two diodes, one is a 780nm (Infrared) diode and one is a 650 (red) diode. It is used because the cd and dvd surface, when burnt, will have a larger "hole" requiring a larger wavelength to read the CD.
5)I suggest throwing them all out. First of all, any CD drive will have a IR diode... not safe for a beginner because you cant see the dot/beam. Secondly they are piss weak. I suggest buying a LPC diode/sled from modwerx or a member here for ~$8 and build it your self. You can get about 250mw out of those diodes. You can start off with a simple LM317 driver for a constant current source to power it, if your on a budget.

All the info can be found here on the forum, just do some searching!

Play safe and don't forget the safety glasses!!

Welcome to the forum!
-Adrian

 

[gusgus]

Thanks Adrian!

Ah, ok. I'll set the CD drives aside and use the DVD diode, it'll just take a quick test to see which leads are for the DVD diode. The reason I'm not waiting for a diode to be ordered is because using one of these LDs is the point of the project. I'll use this as a kind of sandbox and build a proper diode/driver combo later when I have more time. Don't worry, I have access to all the safety gear and know how to handle them, there are gigawatt-power laser labs for visible, UV, and IR wavelengths where I work I will use the LM317s and 555 timers that i ordered to make a driver circuit.

 

[Morgan]

Have a peak at the guide in my sig too. You sound like you have some electronics knowledge already so forgive if it's below you but it does have schematics for a LM317 driver and other tips to go about building your first laser.

I hope it helps.

Don't forget to introduce yourself in the, "Welcome", section here - http://laserpointerforums.com/f37/ - and tell us a little about yourself. I'm sure we'd love to know where you work given the lasers you just quoted!
:drool:
Welcome to LPF! :wave:

M