DIY Homemade laser diode driver

[stackingmont]

i just bought this pot: 10k-ohm-15-turn-cermet-potentiometer-trimmer from radioshack
im not sure if it works for this circuit or how to hook it up, can someone pm me on this?

 

[yuip]

No, no, no!

The circuit shows the diode in PARALLEL with the load, but in reverse! That is not in series..

Do the circuit exactly like its drawn, only make sure you get the pins of the 317 right. I think (not sure) they are drawn in the wrong order (compared to where they really are). There is another pic with the elements pictures, and there it should be right.. Check the datasheet for the correct pinout!



About the diode..
Usually they are placed BEFORE a circuit, in series, to protect from reverse polarity.. But when the polarity is right, they drop the voltage, so you need a higher imput voltage..

In order for this circuit to work from 6V up, the diode was put in parallel with the load but in reverse, which is a "dirty" solution to the problem, as it shorts the battery when the polarity is wrong, but at least it doesn't  drop the voltage, when the polarity is right.

This means the diode does NOTHING when the polarity is right.. It's just there to protect the LD from accidents.


EDIT: If you're not sure, TEST THE CIRCUIT WITH SOME LEDs! They are cheap and hard to kill. Then power the circuit down, SHORT the capacitor (if it's not yet on the LD) and then connect the LD, with the current set to minimum (pot - max resistance), and slowly turn the pot to achieve the desired current..

You also need a way to measure the current. A 1 Ohm resistor in series with the LD is great for this, as you don't have to disconnect anything - less chance of killing the LD and it doesn't affect the circuit (the LD will still get the same current, only the imput voltage needs to be slightly higher, but it's hardly noticable). We discussed this a couple of pages ago. Measure the voltage drop across the 1 Ohm resistor, then mV = mA..


EDIT EDIT: Ground yourself, then ground youself, and when youre done grounding yourself, ground yourself! Then, before you touch the LD, ground yourself! Then ground yourself some more!

True, true. My bad. It is only in reverse.

I think that my first circuit is doing pretty well. And yes, the LM317 pins are numbered incorrectly in Daedal's diagram. I checked 2 or 3 datasheets to get the correct pinouts before I built it. I built a second circuit yesterday, which I'll have to test in a few hours. I didn't ground myself while building it as well as I did with the first circuit, but hopefully it will still work. :

I remember seeing the discussion of measuring the current across a 1 ohm resistor. I have a few and I may try it. IIRC, chimo said that you could wire the multimeter between the circuit and the batteries and still measure the current correctly?

Thanks so much for the help!

 

[Zarniwoop]

If you set your meter to a current scale and put it in series with the LD, you can measure the current that way.
But if the probes slip, your alligator-clip comes off, etc. you can easily kill the diode. If your capacitor is back on your circuit-board rather than directly on the LD, it's almost assured you'll kill it.
The nice thing about the resistor is you can leave it permanently soldered in place, and if you use 1 Ohm it's a direct conversion from mV to mA.

 

[BlueFusion]

you know, instead of all this fuss and bother with a complex and expensive DIY driver, you could always buy one smaller and cheaper see my sig...

 

[yuip]

Thanks, Zarniwoop. Looks like I'll be placing a 1 ohm resistor to measure current.

I also tested my second circuit, and it works fine! I'm off to build my third, and hopefully final, circuit.

 

[amkdeath]

hey guys this may be off topic but:

WHAT?? HUH??? WTF???


I REALLY think ppl shud make seperate threads for their issues, this way ppl can find stuff a lot easier (plus theres that new search engine too)

it will also be more organized, and you wouldnt have to look through 40 pages...

WHen I joined I believe this thread was 25 pages?? Jeez....

just my opinion, even though its completely off topic, I though it was important...


regards,

amk

 

[chimo]

Unfortunately, it has gotten this long by people only looking at the last page or two and then posting questions that were answered (and re-answered) much earlier in the thread.

hey guys this may be off topic but:

WHAT?? HUH??? WTF???


I REALLY think ppl shud make seperate threads for their issues, this way ppl can find stuff a lot easier (plus theres that new search engine too)

it will also be more organized, and you wouldnt have to look through 40 pages...

WHen I joined I believe this thread was 25 pages?? Jeez....

just my opinion, even though its completely off topic, I though it was important...


regards,

amk

 

[Daedal]

I myself am lost with this thread too... so I suggest something...

How about people pour in (and I use 'pour in' because I expect to get 500 PM's for this) all the questions they think should be answered. I will read them all, and add a FAQ section in the front covering all the points...

Now... the rules for this... try to bunch your questions into as little PM's as possible (preferably one). I will read them, note them down and then post it all once I have them all answered. No promise I will reply back to you considering the amount of PM's I would get and already do get... I don't think I wouldn't reply with a simple "Thank you" at the minimum. This will take a little while, so don't PM me asking if I got your PM ;D

The title should be "FAQ SUGGESTION"

Alright... bring it in... this thread should become a full recourse and a good reference. Although I still do recommend people read the 40 pages (an hour or so) because they have the full spectrum of specific answers to specific questions, but a good FAQ in the beginning should strip out all the general and repetitive questions

Thanx for all your help;
DDL

 

[aaronX987]

Another one bites the dust.
I really dont think there is much that you have not already explained daedal. I believe the problem is people like me, not you. A little bit of static sent my diode into cardiac arrest. It died. At least I bought a few spares.

 

[sir._RPF]

HELP!!!!!
Someone know what's the power of a DVD diode ( without lens or something JUST the laser diode power alone ) ?????
Please HELP me and thanks!!

 

[amkdeath]

HELP!!!!!
Someone know what's the power of a DVD diode ( without lens or something JUST the laser diode power alone ) ?????
Please HELP me and thanks!!

ooooookay........ totally not random....

I feel like I started something... its really weird, I feel, well, how can I say this, I feel all "tingly" inside, as if a thousand voices cried out in an instant and then were scilenced.... wait, nvm, wrong quote...

Mabe I shud stop with the quotes and the stuff that is not funny...

anyhow, GOOD IDEA DDL!!!
I personally wouldnet go through all that troubble because:
1. I prolly dont know the answers to all the questions, and
2. I barely have enough time to breathe... let alone answer millions of questions.

DDL I personally think you should start a new topic, sticky it, put the link to the topic in 30 pt font on the front of this thread. This way we have a fresh start. Just my opinion, although I know a n00b's opinion will be beat down and pummled to the point where It doesnt exist.

Once again, BRAVO DDL, you are very very dedicated to helping us all, And I think everyone should at least post a reply in this topic thanking him.

Here is mine:

THANK YOU DDL

 

[Daedal]

Thank you amk.

regards;
DDL

 

[rkcstr]

New here.  Planning on building me a Senkat red laser and a Bluray from Daedal.  I've been planning to build Daedel's circuit here, but I wanted to build a small driver that I could run off lower voltages and would fit in my DX housing.  So, I designed an SMD circuit and am working on building it.  I just got the parts and did a test fit on a scale printout, you can check out the mockup attached (circuit isn't correct, and has been revised, but still has mostly same arrangement, in case anyone notices).

I'm etching the boards myself using a method that should yield very nice boards.  Unfortunately, I have exams next week for my graduate classes, so I can't get it finished until then  :-/

Anyway, the board size is 10x18.5mm and should be less than 6mm thick.  Just slightly longer than the diameter of the dime in the pic.  Test fitting the scale printout was good, I just have to make an actual size mockup of the board to make sure.  But, if all goes well, it should fit no problem by soldering the LD directly to it and capable of outputing 1A using an On Semi NCP1117 LDO regulator (~1v drop out).

I'll be sure to post up some pics when it's finished and my results  

 

[Da_Dude]

Wow!
I hope that works!
Btw,
THANK YOU DDL!!!!!!!!1!1!1!!!!!one!!!

 

[knimrod]

New here.  Planning on building me a Senkat red laser and a Bluray from Daedal.  I've been planning to build Daedel's circuit here, but I wanted to build a small driver that I could run off lower voltages and would fit in my DX housing.  So, I designed an SMD circuit and am working on building it.  I just got the parts and did a test fit on a scale printout, you can check out the mockup attached (circuit isn't correct, and has been revised, but still has mostly same arrangement, in case anyone notices).

I'm etching the boards myself using a method that should yield very nice boards.  Unfortunately, I have exams next week for my graduate classes, so I can't get it finished until then  :-/

Anyway, the board size is 10x18.5mm and should be less than 6mm thick.  Just slightly longer than the diameter of the dime in the pic.  Test fitting the scale printout was good, I just have to make an actual size mockup of the board to make sure.  But, if all goes well, it should fit no problem by soldering the LD directly to it and capable of outputing 1A using an On Semi NCP1117 LDO regulator (~1v drop out).

I'll be sure to post up some pics when it's finished and my results  

Nice work!  I hope you'll let some of us buy a few of those off you...  

 

[stackingmont]

ddl, ik ive been a pain in the rear end with all the questions, but i want to say thank you for this amazing guide and all the help uve supplied me with. because of you, i just completed my very first diy laser using your circuit, and ill tell ya, it works flawlessly! it lights matches, pops balloons, and burns right through black paper. ill post some pics of it when i get the chance. its not too aestheticly pleasing, though, but thats only because i have it electrical taped to a piece of 2x4!

thanks ddl!