Building a laser using a KES-400a , need help!

[Mohrenberg]

yeah with those schematics when you turn the switch on the caps will discharge instantly into your diode and blow it....switch is best placed between the driver and the power source....

 

[pianoman2011]

Don't use that schematic, it will blow your diode the very moment you flip that switch. You must NEVER break the circuit on the output on a constant current driver! The driver will try to regulate the voltage all the way up to keep the current constant. Instead use two drivers and put the switch on the input of the driver(s).
Since there seem to be some confusion about the maths, here's two examples:

For the DDL driver:

R = V / I:
1.25V / 0.04A = 31.25 ohms. (Always go for the nearest HIGHER common value.)

W = U * I:
1.25V * 0.04A = 0.05 Watt. (Always go for the nearest HIGHER common value.)


And here's how for the "kipkay-driver". Works good for lower current standard LEDs.

R = V / I:
9V - 4.5V =  4.5V / 0.04A = 112.5 ohms.

W = U * I:
4.5V * 0.04 = 0.18 Watt.

Jakob, please don' post things you don't really have a grip on. Pyro01, what you need to do is just look some more, there's a TON of great info on how to use this diode.

Oh shiba, my bad. I forgot to draw in the short-out switch. I used this driver (with a cap short out switch that I forgot to draw) for my KES diode and it worked perfectly. I turned off the laser and just pressed the short-out-button each time before I switched from red to violet or vice-versa. It worked out fine. And it's cheaper than using 2 drivers. I know I don't exactly have a full-grip on it, but I'm not completely retarded either :-[ and at least know that a cap will blow the diode. Sorry for providing bad info.

-Jakob

 

[pianoman2011]

Modified: When switching from violet to red or vice-versa ALWAYS turn off the laser and press the Cap Short-Out Switch first. This will prevent cap from discharging into the laser diode and blowing it. The switch has to be a constant off switch preferably a pushbutton.

(again, sorry for misleading)

Modified Schematic:

 

[rog8811]

@pianoman,
I have just noticed your second one shorts out the regulator with the batteries still connected.....not a good idea.

Regards rog8811
[edit]I have thought a bit about what you are doing, I cannot see a foolproof way to do this with 1 driver and 2 switches.[/edit]

 

[lasersbee]

Actually it shorts the output through a 1 Ohm resistor and the Pot... ;D ;D

No t 100% sure... but aren't the LM317 regulators short proof protected
like the LM7805... :-?

Either way... I think the button would be presed after turning OFF the driver
and before switching to the other LD...


Jerry

 

[rog8811]

If you want to short tha cap safely you do this.....
...it still allows the changeover of LD's to be done with a charged cap though.

Regards rog8811

 

[Pyro01]

I really would like to take advantage of both lasers in this diode, but I'll keep looking for a sound driver before I attempt it. I have a drive build to run only the violet laser, but I don't have a problem with drilling out a housing to fit a second switch in there.

 

[Pyro01]

Sorry for the double-post, but since I can post links now, I can post a schematic I found regarding using both laser pointers, does this one look any good to you guys?  The guy who wrote this looks like he's a student of MIT, so hopefully he knows what he's talking about.

http://web.mit.edu/cjoye/www/lasers/BluRay1/BluRay_Simple_Rev5.gif

 

[Pyro01]

Well, as I was soddering the wires to the LD, one of the pins snapped off, it still works, but now it's nearly impossible for me to sodder a wire to a broken pin that's flush with diode, very sad. Maybe I'll go purchase an 803t diode to mess around with if I can't fix this one.