Burner diode report - sort of...

Yes but a 1 ohm resistor is much better. A 10ohm resistor will drop quite a bit of current. It will work, but the circuit will be that much less efficient.

I have my LD running happily at 450 mA's, but is that too much? Also, does the voltage matter? The input to the driver is around 5.7 volts (4 AA batteries) and the voltage to the LD is exactly 3 volts. The LD doesn't heat up that much anymore (I have no clue why), and I have even tried 700 mA's for 10 seconds with GREAT results! It INSTANTLY starts melting ANYTHING that's black and can even start to melt white rubber bands! It can also very easily light matches. I am very happy with it so far, but I have ordered another DVD burner because I don't think that it will last too much longer since I have put it through so much.

700mA holy crap, I think I would never have the guts to drive the only LD I'd have at that kind of current.

laser_freak said:

I have my LD running happily at 450 mA's, but is that too much?  Also, does the voltage matter?  The input to the driver is around 5.7 volts (4 AA batteries) and the voltage to the LD is exactly 3 volts.

Click to expand...

The voltage does matter, yes. It's the thing, that causes the current to flow.
The LM317 driver is set up in a way, that it continuously adjusts the voltage to keep the current constant.

The current and the voltage are directly related, over the resistance of the LD. For every voltage there is only one current (and the other way around - U=RxI). Of course, when the LD heats up, and it's resistance decreases, the driver automatically adjusts the voltage (drops it a little), to keep current the same.


But since you only use four AA batteries and their voltage is 5.7V, this means the driver doesn't get enough voltage to keep the current stable.

You're not supposed to use only 4 AA batteries with it. You need at least 5 alkaline cells or even better 6 Ni-MHs...

The driver needs more than 6V to sucessfully regulate the current.  As long as the voltage is above 6V, the current to the LD will be constant. Since your voltage is bellow 6V your current is not even close to 450mA..

The LD doesn't heat up that much anymore (I have no clue why),

Click to expand...

Well, this is the reason it doesn't heat up anymore. The current is way below 450mA, because you're not feeding the circuit enough voltage.

Many people have made the same mistake, when they read, the driver needs 6V. They gave it exactly that.

But it means, that as their batteries discharge, the driver can not put out the required current anymore.

You need to select the batteries in a way, that when they are almost empty, their voltage is still 6V. Only this way can you have a constant output over their entire capacity.

6 Ni-Mhs would give you 8.4V when full and 6V when empty, and this would mean the current to your LD would be constant over their entire capacity..

To make it smaller you could use two rechargable Li-Po cells. You would again have 8.4V when full and 6V when empty.

I am very happy with it so far, but I have ordered another DVD burner because I don't think that it will last too much longer since I have put it through so much.

Click to expand...

I think your LD is still very much alive.. You just need to start using more batteries, and maybe set the current closer to 420mA and it should live for a very long time.

And don't worry about the voltage going into the LM317, as long as it's above 6V. You could actually give it 37V and the output would still be the same. The regulator would just heat up a lot more, and maybe shut down, to protect itself. But the LD would always get the same current and voltage.


BTW: Do you have any 16x DVD laser, to compare it to? Or is this your only one? I'm still waiting for my open can, and so far i only have two 16x lasers and i really hope the open can is visually a lot brighter.

OOOOhhhhhhhhh!!!!!!!!!!! I can't believe I didn't notice he was only using 4 AAs, The 700mA caught my eye and I didn't really pay attention to the rest. :-[

chido said:

OOOOhhhhhhhhh!!!!!!!!!!! I can't believe I didn't notice he was only using 4 AAs, The 700mA caught my eye and I didn't really pay attention to the rest. :-[

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That's because you have too much experience with lasers, so you don't expect such simple mistakes..

I still remember having similiar beginner questions on the other hand..

Oh trust me I do not have that much experience with lasers. I only know how to build them and some extra stuff, but that's it. I haven't even built my own because I'm waiting to get some goggles first.
I've seen a lot of your posts, and trust me, you know a lot of things so don't try to act noobish. ;D (Is noobish even a word, and did I spell it right?) :-? ;D

chido said:

Oh trust me I do not have that much experience with lasers. I only know how to build them and some extra stuff, but that's it. I haven't even built my own because I'm waiting to get some goggles first.
I've seen a lot of your posts, and trust me, you know a lot of things so don't try to act noobish. ;D (Is noobish even a word, and did I spell it right?) :-? ;D

Click to expand...

I don't know if it's a word or not, but i just said, that not so long ago, i too had some stupid questions about the LM317 for example, simply because i was thinking the wrong way and complicated too much.. That's what i meant with "beginner questions"...

Otherwise i do have some electronics experience, since i work with them proffesionally, but again, it's very limited, because i just organize everything, while others do the developing of the complicated insides. (I just do the user interface, the uP programming and the computer software when necessary)

Lasers are new to me tho, but i did learn quite a bit, by killing many of them.. At least now i know what not to do..


But i'm surprised, that you haven't built a laser yet yourself, due to the fact how long you've been here... So did you just buy your lasers, or don't you have any?

Nope, don't have any. :-[
I have most of the stuff ready, all I need is an aluminum enclosure which I found but haven't ordered yet, a piece of aluminum so I can make a heatsink for the aixiz housing, a vice to press the housing into the heatsink, a new soldering iron since my other one just broke, and some other little things. (ok maybe I don't even have half the things I need yet) ;D
I got a stonetek diode that I'm planning on driving at low currents so it doesn't die that soon, and then after it dies I'll put in the monster I got from TheMonk (the open can) although I'd like to find out the differences between the long open can and the short open can (which is the one I got) just to make sure I don't overdrive the short open can and kill it because it might be weaker than the long open can.
But before I power anything, I need to get some red safety goggles first. Otherwise I'm not touching anything.

chido said:

But before I power anything, I need to get some red safety goggles first. Otherwise I'm not touching anything.

Click to expand...

smart puppy... obviously not one of those who still think they're immortal... and not an old fart who thinks he has nothing left to lose...
;-)

on the other hand, this old fart observes:
521 posts @ 5min/post = >40 hours
40 hrs * $6/hr = $240
...so if you'd just spent your time working at McDonalds instead of helping people here, you'd have those goggles paid for by now!
;D :-? :

@ IgorT:

I am using the LM317T driver circuit. I just didn't know that it adjusted the voltage! I was getting a steady voltage reading from it. For batteries I was told to use two of these http://www.dealextreme.com/details.dx/sku.3273 . I just tried them now, but are they okay? BTW, i am using this http://www.laserpointerforums.com/forums/YaBB.pl?num=1197651171 to measure the voltage and current.

I DO have a 16x DVD burner. The open can diode is MUCH brighter when I run them at the same mA. It also seems to be very sturdy. I accidentally dropped the open can diode when I was extracting it and it was fine! I only have one question about it that you might be able to answer. I tried running my open can diode again at 700 mA's (this time with the better batteries) and everything was fine. But obviously you can't run the 16x stonetek diodes off that much current, but is that because it's not open can or is it because they're from a 16x burner and not a 20x burner?

PS: Thank you for the reply. It was very helpful! ;D

danq said:

[quote author=chido link=1200633213/15#24 date=1203879270]But before I power anything, I need to get some red safety goggles first. Otherwise I'm not touching anything.

Click to expand...

smart puppy... obviously not one of those who still think they're immortal... and not an old fart who thinks he has nothing left to lose...
;-)

on the other hand, this old fart observes:
521 posts @ 5min/post = >40 hours
40 hrs * $6/hr = $240
...so if you'd just spent your time working at McDonalds instead of helping people here, you'd have those goggles paid for by now!
;D :-? : [/quote]

;D ;D ;D ;D ;D ;D ;D ;D ;D
Yeah, I've been trying to find a job, but I haven't had any luck.

laser_freak said:

@ IgorT:
I am using the LM317T driver circuit.  I just didn't know that it adjusted the voltage!  I was getting a steady voltage reading from it.

Click to expand...

Well, it has to adjust the voltage, to keep current the same, when internal resistance changes from heat..

Besides, voltage is the thing, that makes the current flow. So the only way to regulate the current, is to regulate the voltage in a way, that the current stays the same.

When the LD heats up, and it's resistance decreases, the LM317 will automatically drop the voltage just enough, that the current stays the same.. If you activelly cool it (like with a peltier), the resistance will increase, and the voltage will have to go up, for the current to stay constant.

But to do this, it needs a high enough input voltage. The LD needs around 3V and another 3V are dropped in the circuit, so you need more than 6V for it to work. A higher voltage is not a problem for this circuit, but with a lower voltage, the output starts dropping..

 For batteries I was told to use two of these

Click to expand...

Are you using them, or are you still waiting for them? These are perfect for the LM317 driver, because they give you 8.4V when full and 6V when empty. Over this entire voltage range, the 317 can keep the current constant..

But if you were getting only 5.7V from two of these, you should recharge them. As soon as the voltage drops below 6V, your output will start falling.

Some people make the mistake of buying two 3V non rechargable batteries, since they think the 317 needs exactly 6V.. This is the reason they don't get a constant output, untill they switch to two rechargable Li-Pos..


BTW: I know i'm repeating myself, but there are still many people who don't know this.. It's a very common misunderstanding.

I DO have a 16x DVD burner.  The open can diode is MUCH brighter when I run them at the same mA.  It also seems to be very sturdy.  I accidentally dropped the open can diode when I was extracting it and it was fine!

Click to expand...

I find this odd.. What current are you talking about?

From the graph, up to a certain current, the 16x (at least the Senkat's group buy LDs) is better than the open can, and after that current, the open can suddenly picks up and becomes more powerfull. So how can it be brighter at the same current? Where is your 16x LD from?

I also have two 16x lasers, and i really hope the open can is visually much brighter..

I only have one question about it that you might be able to answer.  I tried running my open can diode again at 700 mA's (this time with the better batteries) and everything was fine.  But obviously you can't run the 16x stonetek diodes off that much current, but is that because it's not open can or is it because they're from a 16x burner and not a 20x burner?

Click to expand...

It's because they're not made to withstand such high currents and output power..

They are manufactured differently.. It's not about the can..

A faster DVD burner means the disk is spinning faster. This means, the laser has to be more powerfull, to be able to burn the same change into the surface of the DVD in less time..

So yes, it is related to the DVD speed. But the reason is, that it is created to be more powerfull, so the DVD can write faster. And the faster, the better for us...


My first open can should finally arrive tomorrow. I can hardly wait.
I already prepared everything.. The enclosure, the peltier for pumping away the heat, a tiny fan made from a vibrator motor and a tiny helicopter tail propeler, and of course a temporary 317 driver circuit, that will have to do, untill i finish the buck converter, that can regulate the current from a single Li-Po.. (I like my lasers small)

Ok, my NEC 7191A finally arrived.. The shop said they sent it on friday, but the label says, they sent it yesturday...


I already dissected it, and found two cans.. One is in a weird square piece of metal, that has a thinner round tube with a lense on top.. The other is directly in the big chunk of metal..

Luckily both are cans, so i don't have to worry i'll get a flat chip red... But which one is which? I'm gona have to cut the metal away, it would seem..

IgorT said:

Ok, my NEC 7191A finally arrived.. The shop said they sent it on friday, but the label says, they sent it yesturday...


I already dissected it, and found two cans.. One is in a weird square piece of metal, that has a thinner round tube with a lense on top.. The other is directly in the big chunk of metal..

Luckily both are cans, so i don't have to worry i'll get a flat chip red... But which one is which? I'm gona have to cut the metal away, it would seem..

Click to expand...

Igor, the red is probably the second one. But you could just fire up each one, to about 75-100mA, and see which is which - maybe even before taking them out.

DanQ

danq said:

Igor, the red is probably the second one. But you could just fire up each one, to about 75-100mA, and see which is which - maybe even before taking them out.
DanQ

Click to expand...

You are right.. It was the other one.. I took the weird holder appart, and the diode had a can, without a window, with a window glued on top.. I guess it can be removed, and it's an open IR, but i don't need it anyway.. I'll use it for testing my buck converter driver, that can regulate the current from only one Li-Po cell, and keep it constant down to 2.7V...


The second one was a pain to get out. It was not only glued, but also soldered in place.. The removal was quite destructive.. In the end i found two holes on each side of it, with glue in them, so i dug out the glue, and wedged the LD free..


After that, i noticed that one of the pedestal edges is slightly bent, but i don't think it was me. I didn't go that far in..


Anyway, this is a pic of it i made...


EDIT: I made a better pic with another camera.. Replacing the old one..