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DIY Homemade laser diode driver

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OK

I have built my driver to the schematic, does it matter what voltage I use for the input (7v DC)?

And the higher the resistance on the pot the lesser the current to the diode right?
 





WarezWally said:
OK

I have built my driver to the schematic, does it matter what voltage I use for the input (7v DC)?

And the higher the resistance on the pot the lesser the current to the diode right?
Click to expand...

these questions have been answered millions (AND LITERALLY MILLIONS) of times on this thread. read it thruogh guys. and DDL is in the process of making an FAQ thread, which should help.

u need at least 6v input, 9v if ur using blu-ray. the more input= more heat. do not use 9v batts, or 4 AA/AAA 's as they will sag.

a few pages behind this is a mini FAQ section, read that.

if problems persist, MAKE A NEW THREAD

regards,

amk
 
Just finished my laser. I assembled a small box for it using the cover of an old hardcover book.

I wont clutter this thread, see here for more: http://www.laserpointerforums.com/forums/YaBB.pl?num=1198896548

Just wanted to thank Daedal & Co. for going through the work of putting together this resource. Daedal's circuit worked flawlessly and I didn't kill any diodes getting things working. I'm currently driving the diode with about 225 mA of current and it's burning well :D
 
yawn, 46 pages in 2 days. my eyes hurt.

time to go to RS and then to goodwill to try and find a 16x burner
 
hey stupid question-but what kind of capacitor does this need--i have like 100's--small and big--and am not sure what will work in it. :-?
 
How does this look? Some errors that I know I made, forgot the switch. C2 will actually be a lot closer to the LD.

C3 is 100uf 50 volt and 1&2 will be dug out of a big tub of ceramics that I have as soon as I understand the stupid codes on them. Is it alright to use 100uf instead of 47uf. I read earlier that I'd want to avoid this because they don't absorb high frequencies as well. Will including the smaller C2 fix this?

What happened to the days when the radio shack employees could actually answer questions about the merchandise they sell?
 

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depending on R1 and R2 this looks like the demise of your LD. this is a constant voltage source, not a constant current source
 
Oops I guess I based my circuit on the drawing from the back of the RS 317 package. I'll redraw it and get it posted. Thanks


Ok here it is. How does this look? And does anyone know what the outer diameter of the Aixis module is, so I can drill the right sized hole in my box?
 

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that's better. for a red LD 12V are too much. c1 and c2 are a good idea indeed. if you plan on routing long wires to the LD, it'd be better to solder C2 directly on LD's leads. 10-100nF should do fine.
why is the switch there?
 
I don't see a switch -- He modified his circuit to a CC rather than a CV.

You can also add a 1 ohm resistor going to the LD.  This provides a test point to measure current (mA)  

I use a 78L05 voltage regulator for my Blu and limit current with a resistor.
Don't forget the CAP across the diode !!

Mike

Also, If high frequency is a concern, you can add, say, a 0.1 mfd ceramic into C2 but the CC circuit has always seemed stable to me.
 
I left the switch out of the schematic. Those things that I added to Vout are the Rheostat and R1 to the best of my trackpad drawing ability.

I must have read something in the past 45 pages wrong, but I was under the impression that because the resistance is set, and I'm adjusting the output current to be what I want that the voltage, no matter what the input, would be alright for a LD. I was planning on using 2 lantern batteries to test it just for now and then in the future switching to something a little smaller. One of my batteries still puts out 6.2 volts but they were really cheap so I don't know how long that will last. I can try it with just that one battery.

How does the voltage drop on one of the 16x dvd LD's compare to a normal red led? If I was to hook 7-8 of them in series up to this circuit would that approximate a LD. What kind of current should I aim for with the LD? This is my first laser so I don't want to push it too hard, but I would like to be able to burn with it.
 
I went ahead and build the circuit on a breadboard. I guess I don't have any spare protoboards so I'll have to run back to RS.

The two small ceramic caps I used were from a grab bag I have, most of them don't even follow the normal labeling, but eventually I found some labeled 101J, so 10 pf right? will this be sufficient to solder to the LD or should I find some .1 or .01 mf caps?

I tested the circuit using a single red led. I left the rheostat at it's max so the total resistance with the 5 ohm was 30.5ohms. I first powered it up normally and measured 1.85V across the led. Then I rewired it with my dmm in series and measured 40.4ma.

Does this seem right? If I get these same results after it's all soldered in place should it be safe to add in the LD and crank down the pot?
 
That current with ~31 ohms appears about right for ~40 mA. Which LD are you going to power up ?? Red ?? If so, you have your starting place because with the pot set to max, that will be the starting current.

Mike
 
jtbarclay said:
I went ahead and build the circuit on a breadboard.  I guess I don't have any spare protoboards so I'll have to run back to RS.

The two small ceramic caps I used were from a grab bag I have, most of them don't even follow the normal labeling, but eventually I found some labeled 101J, so 10 pf right? will this be sufficient to solder to the LD or should I find some .1 or .01 mf caps?

I tested the circuit using a single red led.  I left the rheostat at it's max so the total resistance with the 5 ohm was 30.5ohms.  I first powered it up normally and measured 1.85V across the led.  Then I rewired it with my dmm in series and measured 40.4ma.

Does this seem right?  If I get these same results after it's all soldered in place should it be safe to add in the LD and crank down the pot?
Click to expand...
101J=100pF, 1nf=102, 10nf=103, 100nF=104,... 100pf is...err...not enough. use a higher value if available.
u could use 4 1n4001 diodes in series, they pretty much resemble a red LD in term of forward drop.
 
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