Laser question

A link would help. I'm guessing just the right voltage. GH

Laser diodes do have a nasty habit of blowing up if maximum current is exceeded, even very briefly.

The active junction is remarkably small, and heats up correspondingly fast.

Can't remember when I first heard that - probably back in 1992. Heard it early enough that I didn't ever manage to test it, so I can't guarantee that it is true.

A resistor at minimum, preferably a real current source. Laser diodes can be operated constant-voltage, but the voltage has to be just right. You could experiment carefully with an adjustable power supply. Or just dump in 20 mA and be safe.

It's possible that the laser module has a built-in resistor or current limiter. Experiment.

When in doubt, search what others have done to power their lasers: Kinda looks like all are current driven, not voltage.

If in doubt a series resistor with the voltage supply to make sure it can't reach the absolute maximum current rating of the device.

I have retired the odd one by accident. Bare laser diodes need constant current drive if they are to survive longer term. This sounds like a module that contains a suitable driver and will work on 2-8v nominal.

The constant current might just be provided by a cheap resistor which could mean that it gets a bit warm on >6v. They are definitely a lot more tetchy than LEDs about this sort of thing.

"

I will look for a heat sink that I can attach to it.

Andy

Ahh.. OK those specs look nothing like you first posted. I would say that is a bare diode, and wants a current drive. You can make one out of an LM317 and a resistor.

George H.

Hard to tell. Got a link?

Cheers

Phil Hobbs

Well, for three bucks you can get a few to blow up and a few to use. ;)

Cheers

Phil Hobbs

Could you give some details on that?

Thanks, Andy

Have a related ?.

Working on the power supply for the laser diode.

Using resistors, I used a 5 volt transformer and brought it down to 2.5 volt using some 1/2 watt and .25 watt resistors.

If the laser outputs 5 mW and .25 watts = 250 Mw, then am I o.k.?

Andy

Looks like this is the one the OP meant, though the data sheet doesn't agree with the specs...

So the OP posts a link to the wrong device, and the supplier prints different specs to that device's data sheet. I don't see this ending well.

Cheers

No, this is what I will use as it is much cheaper than the adjustable one.

"

googles, lm317 current source

GH Not so good fro small currents but perfect for 10-100mA

I have a 5 volt power transformer.

Do I get it down to 3 volts first?

Then connect positive to Vcc ?

Does the negative go straight to the laser diode while lout goes to the positive lead of the laser?

Andy

Thanks to everyone's help, I am learning even if it seems slow. :-)

Andy

Hmm, well definitely buy more than one laser diode... 'cause I'm guessing you will blow some. You could put a few 1n4002 in series and use those for a dummy laser diode. Read that whole page on LM317 current sources... Make sure you understand how to choose all the values. (There is a connection from the output to the adjust pin of lm317)

Maybe read some about how the lm317 works.

George H.

This is becoming quite a complicated project.

I can buy a laser with it's own power supply, but I would prefer building my own.

This is it's specs. Should I be looking at the working current?

Material: Plastic and copper Operating Voltage: 3V DC Working current: < 40mA Input power: 150mW With red dot Wavelength: 650nm Output laser power: < 5mW