2X AA flashlight mod

It seems that quite a few people want to buy a LD and an AixiZ, slap it in a flashlight and burn away. I'm sure we'd rather they didn't as more than a few will likely damage an eye or two. But as long as the "Instructions" are out there anyway I'd like to see as few diodes die a meaningless death as possible.

So someone please tell me if I'm wrong as I CANNOT say from personal experience with these diodes.
But I have used this before on a DVD burner diode, and this seems to be what people on the forum are saying would be the bare minimum to make it last longer than 5 minutes total.

See the pic below

Radio Shack part numbers are:
272-135 for a 2 pack of .1 uF ceramic disk capacitor (you'll only need one)
and 271-1301 for a 5 pack of 10 Ohm Resistors (you'll need four)

From what I've read, this should provide about 240mA from fresh batteries. IF you were to use Lithiums, it would provide more like 400mA which would be a VERY quick death without active cooling.
OR you could use 3 NOT 4 of the resistors and with regular batteries they would supply around 180mA, and with Lithiums around 300mA.

Personally, I'm going to use an adjustable regulated supply at first. But I may try to build a tiny pen laser later...hmmm...I wonder how much current a CR2032 would supply???

The CR2032 might last a minute or two. You would be pulling much more current from it than it was designed for. The spec. sheet follows:

http://www.gpbatteries.com/pic/GPCR2032_DS.pdf

One way to make the laser small would be to use a AAA battery with a boost circuit. I have been looking for an LED flashlight with this configuration but they are hard to find and the Fenix LOD is too expensive. Now if we move up a notch to a single AA battery powered LED flashlight, they are much easier to find.

Regarding your circuit I understand the resistor configuration. I use those exact same resistors. But why are they saying on the other forum a .1uf capacitor will prevent voltage spikes? How can this be accomplished with a .1uf capacitor?

I did a power check on my flashlight mod LD.

DISCLAIMER: Keep in mind that each LD is different and will not have the same VI curve as mine! These figures should be used to "ballpark" components only.

My LD had a voltage of 2.75V when running at 200mA for an electrical input power of 550mW.  

The original LD I had in that mod only ran at 180mA.  The difference is due to the VI curves being dissimilar for each diode.

Sorry Gazoo, I was mostly joking about the 2032...but now you have me thinking, maybe a couple in parallel would work for a few minutes without exploding.

As to the Caps, I personally think that 47uF is a bit too big, but that's just me and I'm ready and waiting to be told I'm wrong.

I was really posting because a few threads seemed to be getting off topic with people asking if they could build one "like in the video I saw"

Chimo, I'm with you that each LD is different. Even ones from the same lot can have very different power curves. But I think this would be in the ballpark based on the datasheet for the GB diodes.

And again please, someone tell me if I'm leaving something out.

Ok...Just to let you know..

I built a Mini-mag laser using an open can diode from a 20X dvd burner.

All I did was to put a 47Uf 32 volt cap across the leads.

It goes directly to the batteries..and I am using NEW Energizer e2 Lithiums.

It has been my best burner....and I run it 15-20 seconds at a clip max.

Total I can't even begin to guess at how long it has been on......

So...Yes..you can go POOF your first try....

You can get "Lucky" and run it till it dies and just be happy.

I know I will kill it..but I really don't care...I'll just change the diode.....maybe then add a resistor..

It was my first home made laser...and still burns great!!!


Good Luck....

Larry

Larry,
I have had nothing but good results with my open can diode..it seems to be a totally different animal than a closed can. I have no idea exactly what the difference is in the design except as Chimo pointed out, the heatsink pedestal for the LD chip is bigger. I would love to be able to speak to the designer of the open can diode. I know it will never happen, but the first question I would ask is why leave it open? Was it to cut costs or is there other benefits?

a_pyro_is said:

Sorry Gazoo, I was mostly joking about the 2032...but now you have me thinking, maybe a couple in parallel would work for a few minutes without exploding.

As to the Caps, I personally think that 47uF is a bit too big, but that's just me and I'm ready and waiting to be told I'm wrong.

Click to expand...

Actually I am hoping you will be told you are right...I am just going by what was recommended and has seemed to be the norm. I am looking at Sam's Laser Faq and the circuit described there for current regulation (which is very similar to Daedal's circuit) uses a 22uf at the input preceeding the LM317, and a .1uf across the laser diode. So now I am beginning to wonder...

Gazoo....I don't know...all I do know..is that the only advantage that I can see of the closed can diode is the fact that it can be handled with human hands and not be destroyed!

THe open can diode is just a superior design, but more fragile TO THE TOUCH by at least a factor of 10

Open can diodes represent a tradeoff.....

Yes they are more powerful (Mw) and can take a lot more current without popping into an LED, but they are very fragile animals to work with!!!!!

I just can't wait to see what the next generation diode can do!!!

I won't build another red burner on anything other than an open can 20X diode if given a choice from the current pack!

Larry

if you use just resistors, all the wasted power has to go somewhere, and guess where it goes?into heat on the resistors! you may give the didoe the right voltage, but then you have some hot resistors frying your didoe from heat!

im trying the same thing but my laser is to weak to brun any thing .im hooked to 2 aa baters what is a 47Uf 32 volt cap .and how are you focusing, im use a old laser housing not working well . but i can run cool with a heat sink a brass washer drilled to if ld cap a 16 x i got from Stonetek . :-?

were can i by good ld 200mw +?

a 47Uf 32 volt Capacitor...

A 47 Microfarad, 32 volt capacitor.

Don't check my spelling..hehehehe

A simple electronic component that acts as a Buffer and keeps the spike of voltage when you turn ON the laser, from blowing out the diode!

It is wired in parralel to the diode.....

Google is your friend

Larry

Things,
As for the resistors producing too much heat.

If you assume 2.4V forward drop on the LD that leaves .6 V on a 2.5 Ohm Resistor = 240 mW in a 1 W resistor. Now assuming a runtime of 60 Seconds that gives us 14.4 Joules or just short of 3.5 calories. And finally assume that the resistors are in the AixiZ case (one of which I've never seen) and that the case weighs at least 10 Grams (sounds close to me). So, 3.5 cal / (10 Grams Brass * .09 cal/Deg. C/Gram) Should raise the temp by a little less than 4 Deg. C. Even if the heat had nowhere else to go.

Am I in the neighborhood? It's been a long time since I've used this stuff. :-/

Please don't think I'm arguing that you shouldn't use a regulated supply. I think a regulated supply is by FAR the best way to go. I'm just hoping to keep a few people from spending money on a LD only to have it fry instantly.

I know all this info is already on the forum, that's where I found it. But the search button doesn't seem to work on everyones computer. And much of it wasn't in Experiments & Modifications or General.