[n00b needs help] Problems with 200mW red laser diode

[Lebrelz]

The doctor, sorry if you haven't understood me well, I can't speak english well.
What I said about the resistor, was that I tested my diode in the flashlight (the lantern, read the instructables link i post) which outputs 2.4V from 2 AAA batteries, 1,5V each one. To do that I think ther's a resistor inside the lantern's driver. Can you understand me? So ther's already a resitor in series with the laser diode, just what you say in your post, but not the correct value. And please, translate this phrase into simple english "Don't ever rely on a battery's internal resistance to protect a diode.", I can't understand.



(i think lantern's bulb is about 100 mW). (I can't explain well in english, uderstand me)


And with the die4laser driver, I didn't see details because, when I started to read the main page, I saw something for an IR diode, and I thught people weren't undertsanding me.

Sorry, as you can see, I speak english as bad as a dog.

I just wanna learn, I read your post with interest, you can trust me. And If my post was offensive, I apologise. I was very angry because I blew the diode.

[kaz]

Also i forgot to mention if you do get a dvd diode to run and run well the Axiz housing might not get rid of the heat very well so i would surgest not keeping it on for more than a few of minutes at a time to prolong the life of the diode say 3 minutes on and 2 minutes off to let it cool down if your going to run the diode on full power, Kaz

[kaz]

Dont worry about your English its almost as good as mine and im english i just cant spell for c**p what i would surgest is for you to take your time , dont rush into the prodject have a good look around this site using the search tool and using specific words like ( laser driver) ( laser power supply) as i said befor its all on this site nearly everything you want to know about lasers/scanning/power supplies etc

[Lebrelz]

thanks kad, my idea was to power on no more than 30 seconds. If I do it, it'll be a burning laser. Maybe one day I'll make a greater cooled one, to make a scanner or something similar

[kaz]

also it would be handy if you have any testing equipment like a multimeter for testing the actual voltage/milliamps befor you connect the diode to the battery/power supply,

[Lebrelz]

Yea, I know, but how to measure current before connecting the diode? making a short circuit and putting in serial the multimeter?

[kaz]

we all have to start some where if your willing to learn there is lots of information on this site you could spend a week going through all the posts and never read the same one twice

[kaz]

if you are connecting up to batterys and you are not limiting the current and letting the diode draw the amount of current it needs i would say that you might be better off using some batterys that have been used a bit so they sont put out there max voltage as i dont know what the max voltage is for your particular diode it might be safer for you to use the rechargable batterys as these will only put out around 2.4/2.8 volts max and just adjust the current with a small regulator (varible resistor), keep the resitor at the highest amount of resitance and slowly turn it so the amps start to come through slowly the diode should get brighter and brighter

[kaz]

have alook at this video on you tube i think its speaks for itself
http://uk.youtube.com/watch?v=Xz4v8g...eature=related

[The_Doctor]

dont know if this is going to help but i put two of the doctors rohm diodes into two flash lights i never used a resitor of any type also the batterys i used were new duracell batterys...

...use a rechargeable battery like a pair of ni-mh that would give you around 2.4 volt fully charged also the diode should only take the current it need

Nay, nay and thrice nay!!
Trust me, I'm a... Never mind, just don't.

First, a 2.4V battery won't overcome the 2.7V drop on the diode so nothing will light up, and the moment you added enough volts to do that, the diode WILL take more than it needs! Violently, if you use NiMH or lead acid. Not the battery's fault, it's just that they don't limit their currents with high internal resistances and if you don't either, you will burn those diodes and I don't care what some wiseguy on YouTube says about it. USE A RESISTOR! And use more volts than you need, calculating your resistance for that voltage. That way it won't matter what kind of battery you use, and you'll have something you can control.


Edit, no worries, I'm not offended by anything here, I'm just hammering the point because it's important. Don't assume there's a resistance in the head of the flashlight laser, or in a battery. Add your own, and measure the current in the circuit to confirm that it's right. I see that Kaz has since mentioned using a variable resistor. Good idea, but even better is to have a few fixed ones, between 1 ohm and 10 ohms, more if using 12V, as I mentioned before. The problem with variable resistors is that they start slow, and toward the last tiny bit of turn left in them, they make the current leap high. Very hard to control. Using a chain of low-ohm resistors is far easier and safer.