Driver Circuit assistance request

[Trinity]

Hello Guys,
I don't really know if I should start a new topic but its my first time posting so..forgive my ignorance
Here is my situation. [Stumbled uppon a "how to make a burning laser" video] + [remembered my old broken LG DVD recorder] = Laser Fever
I got the LD from the DVD, found the prints of the driver from a design by ROG8811 and other similar ones from the forums.

Attached is my driver circuit setup. I know its a bit sloppy, but i just wanted to test it first.
Have i done something wrong?...apparently I did since I burnt my diode... :'(
I used a 9 volt battery to power the driver. But as soon i connected everything and pushed the button, the diode flashed brightly for a moment and then it was reduced to a very weak beam spot. Uppon focusing the beam, all i got was a shape similar to this :     _._
Can anyone see if I have connected something wrong? The potensiometer maybe..or could it be the 9 volt battery, although i was under the impression that the regulator chip would lower the input voltage to a lower constant output.
Any advice is appreciated
The first LD is pushing the daises from 6 feet under
I hope I 'll have better luck with the second one(as soon as I manage to find one)

Thank you

 

[lasersbee]

Well the circuit looks good except for the Push Button switch...
It should NEVER be on the output of the driver.... you should put
it between the batteries and the input of the driver on the positive
power line...

If you have already used this setup... you will have blown every
LD that has been connected to it...  
The driver charges the capacitor to way over the LD rating... and
when you push the button... all that over-voltage dumps into your
LD and blows it.... :'(


Jerry

 

[Trinity]

I see your point there
and it does make sense even to an electonics newbie like myself  
Too bad i did not investigate further before the final step...
Ohh well, I guess I will have better luck next time.

Thank you for your help Jerry

Marc

 

[rog8811]

...I am afraid the horse has already bolted but I have just shut the stable door on my website... :

You are the second poster in a week who has put the switch on the output end of the driver, I didn't think, when writing the tutorial, that people would get it wrong but if you have never done it before how would you know?

It now tells builders that it is important to put the switch between the battery and the driver, never between driver and LD.... Sorry it was too late for you OP.

Regards rog8811

 

[Trinity]

I learn from my mistakes. I am sure most people here have blown an LD or two
I would like to ask another question if I may.
I measure the voltage on the battery side of the driver and it was 8.2 Volts. I then connected my meter at the LD+ and LD- of the driver and it was just a little lower, 7.8 volts...shouldn't it be much lower than that? Does this mean that maybe one of the circuit components is damaged?
Or is that normal and I am asking meaningless questions..

 

[rog8811]

Was that measured without a load? If so it means nothing, put in a test load (4 X 1N400 series diodes, even the blown LD might do) and check again it should read around 3v.

Regards rog8811

 

[Trinity]

Yes, you were absolutely right. I used the damaged LD and the output I measured was 2 - 3 Volts.
Thanks again

 

[Bionic-Badger]

Finally, someone who uploads a photo that isn't a 3000x2000 rectangle of blur!

You'll need the 1ohm resistor in series with the diodes to actually measure current. You could even put one in line with the LD, but it'll soak up power. The best thing to do is use the dummy load (4x 1N400x diodes + 1x 1-WATT 1ohm resistor), set your current to the target (for the open can reds you can get in group buys, about 350mA), and desolder and short the leads and then solder the laser diode in.

Make sure it's well heatsinked. I had my whole rig set up, turned it on and was happy to see it bright and lasing, and then it dies due to a lack of heatsinking