DVD "reader vs burner" and "speed" questions

[daveindelaware]

If this was already covered somewhere, then please accept my apologies and label me a n00b (which I already know I am) and spam me with "use the search" function (which I did but wasn't seeing this exact subject off-hand).

I'm curious as to what the difference is between a DVD burner and a DVD reader? I mean, I know there are drives that can only read/play a DVD. And I know that there are drives that can burn/record DVD's (which can also read). That's not my "confusion" between the two.

My question is: Does a DVD burner use the same LD to burn and read (determined by the current?), or does it have two different LD diodes (one to just read, and one to burn)? Is it a matter of current passing to the diode that determines if it's reading or burning? Does a DVD drive always use a red LD?

Also, are DVD read-only LD's worth harvesting if you're not worried about burning anything? Would they only be 5mW or less?

And finally, is there a "general rule of thumb" guide somewhere that states the relationship between drive speed (6x, 20x, etc) and the typical output power (mW) you can get (w/ the proper driver of course)? For both read-only DVD LD's and burners?

Thanks for any enlightenment you can provide.

 

[KiLLrB]

The burn diode and read diodes are separate and the read is usually IR and useless. The burning diode is usually visible red.

 

[daveindelaware]

Oh, really? I thought only CD drives used IR and DVD drives used all red. :yabbem:

So, is it safe to say that any kind of reader is IR? Well, except for BluRay I guess?

 

[KiLLrB]

Oh, really? I thought only CD drives used IR and DVD drives used all red. :yabbem:

So, is it safe to say that any kind of reader is IR? Well, except for BluRay I guess?

I dont think every DVD player uses a IR diode to read but everyone i have disassembled has been.

 

[jaycey]

The burn diode and read diodes are separate

In some cases combined in the same die?

 

[pullbangdead]

Sorry killrb, no.

DVD reading and burning are both done with red, and they're both done with the same diode. In burning mode, it's high-power (given by just supplying higher current/voltage) and driven pulsed. In reading mode, it's the same diode, but driven CW (or possibly pulsed in sync with the disk, but it need only be driven CW for it to work, which is simpler) at low power.

The IR diode is for reading/burning CDs, and is powered in the same scheme as reds are for DVDs.

Reader-only drives will generally have only low power diodes, because that's all that is needed, and it's cheaper. But DVD is always red, and CD is always IR.

As for the red and IR being on the same die, no, they're not likely to be on the same die, but they may be mounted in the same can very easily. They can be mounted physically and electrically in connection with one another without being on the same die.

 

[daveindelaware]

Oh, so CD's use IR, and DVD's use red? That's what I thought, but what do I know? LOL.

Would the LD from read-only DVD drives be worthwhile to harvest? What sort of mW could one expect?

Again, I'm not interested in a burning laser from the harvest. But I'd like to be able to at least see the dot (and the beam if possible).... I have a few old DVD drives laying around and just want to know if I should harvest the LD's or it wouldn't be worth my time.

Given what was said about being pulsed vs CW and different powers, could you theoretically build an adjustable red laser at variable power outputs based on the current being supplied to the LD?

Thanks guys!

 

[KiLLrB]

Sorry killrb, no.

DVD reading and burning are both done with red, and they're both done with the same diode. In burning mode, it's high-power (given by just supplying higher current/voltage) and driven pulsed. In reading mode, it's the same diode, but driven CW (or possibly pulsed in sync with the disk, but it need only be driven CW for it to work, which is simpler) at low power.

The IR diode is for reading/burning CDs, and is powered in the same scheme as reds are for DVDs.

Reader-only drives will generally have only low power diodes, because that's all that is needed, and it's cheaper. But DVD is always red, and CD is always IR.

As for the red and IR being on the same die, no, they're not likely to be on the same die, but they may be mounted in the same can very easily. They can be mounted physically and electrically in connection with one another without being on the same die.

Oh I was misinformed my apologies and thanks for the clarification :beer: the drives i took apart had an IR diode as well as the red i was under the impression the IR did the reading for the DVD but I am guessing that is just for reading CD's is this correct?

 

[billg519]

The reader diodes will be low output. They are good for practicing handling and extracting diodes. You could make a 5mW pointer if you wanted to. You would see the dot, fog would be needed to see a beam. A DDL driver set up with a pot and a max current resistor will give you a variable output laser. I made a red labby that is adjustable power.

 

[photonaholic]

Oh I was misinformed my apologies and thanks for the clarification :beer: the drives i took apart had an IR diode as well as the red i was under the impression the IR did the reading for the DVD but I am guessing that is just for reading CD's is this correct?

Yes that is correct.

 

[KiLLrB]

Yes that is correct.

Thank you sir :beer:

 

[daveindelaware]

The reader diodes will be low output. They are good for practicing handling and extracting diodes. You could make a 5mW pointer if you wanted to. You would see the dot, fog would be needed to see a beam. A DDL driver set up with a pot and a max current resistor will give you a variable output laser. I made a red labby that is adjustable power.

A 5 mW pointer from a DVD reader sounds just fine to me. Would any of the readers only give you 5mW, or could some be a little more (like 10mW)? That was the foundation of my previous question regarding speed. I'm curious if anyone has ever done a comparison or tests to determine what power of LD is in certain speeds of drives. For example: a 10x reader would yield you a 5mW LD, but a 30x reader yields a 10mW LD... Or is a reader always going to be limited to say 5mW?

Thanks for the discussion everyone. It's helping! And it sounds like it's worth harvesting the LDs from DVD readers after all, since I'm not worried about burning stuff.

 

[photonaholic]

That's the spirit Dave, experiment!!

Give it a try and post it here.

Everyone has a few bum DVD drives laying around.

 

[daveindelaware]

That's the spirit Dave, experiment!!

Give it a try and post it here.

Everyone has a few bum DVD drives laying around.

Thanks for the encouragement! I will experiment, once I actually have the time (and money) to build a few DDL drivers!

I am always on the lookout for DVD drives laying around....

 

[photonaholic]

That driver should cost no more than $2 to build.... You can salvage most of those parts from almost any broken electronic device. Even if you purchased everything new, under $5 is a fair estimate.

To "make" a heatsink for the LM 317, just use an old PC heat sink, and drill a hole in it, run a small bolt through the hole, a washer and a nut.

The LM 317 is about all you need to actually buy.

 

[Eudaimonium]

I strongly disagree about following that diagram.

The LM317 regulator chip is supplying the current that is set by resistance between his middle (out) and left(ADJ) pin, and it is easily calculated:
1.25 / desired current in A = resistance in ohms.

Forget the pot, two 10 ohms, and rectifier diode.

All you need is three components:
LM317 (or LM1117 if you can find) regulator IC, resistor and output capacitor (anything in uF range is good, the more the better).
For weak red LD diodes, you should not puch above 50 mA of current to it.
22 ohms is a resistor to be used in such case.

Just a quick reference table:
PHR bluray diode = 100-125 mA = 12 - 10 ohm
LCC/LOC diodes = can be pushed to 500mA, = 2.5 ohms (2.7 ohms or similar reccomended)
IR diodes from 52X burners = 200mA max = 6 ohm

Considering your involvement level I don't think you gonna need this right now but anyway:
SF-AW210 6x bluray diode= 170mA max
GGW 6x diode = 220mA max (can be pushed further but you are taking chances)

Also, rarely you will find 16x SCC diodes which are not to exceed 300mA.


Good luck!