# Need a brief explaination mW, mA laser diodes.

Discussion in 'General Electronics Chat' started by rp_anon, May 20, 2012.

1. ### rp_anon

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Hi, I am wanting to make a burning laser! But my knowledge of electronics is minimal!

I have found instructions for making a laser driver which provides a current up to 250ma.
http://www.rog8811.com/laserdriver.htm

The diode I have found can output 100mW @ 200mA, and 230mW @ 320mA when pulsed at 2khz. Is the mW output purely based on the current? ie increase in the current leads to an increased mW output?
http://www.ebay.co.uk/itm/160690032152?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649

I guess that just means I set the potentiometer on my driver to 200mA and the diode will output at 100mW?

But if I pulse the current at 2000 times a second and set the potentiometer to 320mA the diode will output at 230mW? Which of course is much more desirable!

Is it difficult to get the current to pulse at 2khz? I have made the driver and have the +- output leads.... would the components that make the current pulse fit after the output from the driver or would the entire driver have to be redesigned? Which leads me onto.... what would I have to do to get the driver to provide 320mA?

And one last question. The input voltage to the lm317 voltage reg is 7.2v on the driver design. Can this voltage be anything within the limits of the lm317.... ie can a just use a 9v battery!

rp_anon, May 20, 2012

2. ### davennModerator

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Hi Rik
welcome to the forums

I have allowed this post, as long as it doesnt get out of hand
generally most electronics forums are very wary of posts on subjects where the poster could seriously harm themselves or others

Please keep in mind the dangers of lasers of this power level. At 100 - 300mW they may not actually burn any material, they will surely destroy eyesight in a brief instant
I personally havent had any construction project experience with lasers over 100mW

About the LM317, you will need an input voltage ~ 1.5 to 2V higher than the required output voltage. Also keep in mind a small 9V battery isnt going to last very long drawing 300+ mA

what sort of materials were you planning on burning holes in?

cheers
Dave

davenn, May 20, 2012

3. ### poor mystic

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Hi Rik, and Dave
I am very afraid of lasers, just like anybody else who has managed to survive the folly of youth. My precautions would seem extreme, and I would still fear accidents. I would never experiment with them in a room which was used for anything other than physics experiments, and I'd want to find a competent laser physicist to assist me.
I'd be conscious that if someone were to be hurt by my laser, no matter how accidentally, it would be my responsibility.

poor mystic, May 20, 2012
4. ### (*steve*)¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥdModerator

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I would be keen to know if you have appropriate safety glasses, have removed any likely objects from which one might get a specular reflection, and remember the phrase "Do not look into laser with remaining eye".

I have a couple of lasers with power in excess of 10mW, and they're certainly not playthings. I wouldn't want to be in the same room as someone playing with one.

(*steve*), May 21, 2012
5. ### jackorocko

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Man I always wanted one of these, but after reading this thread I am thankful I never tried. I like my eyesight!

jackorocko, May 21, 2012
6. ### (*steve*)¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥdModerator

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The "safety" feature is often that these devices are very poorly focussed.

However, I've seen some home-built laser cutting devices and these things are seriously dangerous -- since they are definitely anything but "poorly focussed".

Definitely scary. I think if you're not somewhat scared by them, you shouldn't be working with them.

(*steve*), May 21, 2012
7. ### davennModerator

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The strongest ones I personally have seen in action were in 2 different situations

...one in a metal cutting place that use a CNC machine to cut holes in sheet metal for me. the guy just programmed in my the hole coordinates into the machine, took my sheet of aluminuim a zillion zaps later ( maybe a minute or 2 in time) out came my aluminium with many rectangular holes in it
So so cool .... metal cutting usually uses Argon lasers up ~ 30W

the other cool use was at the NIWA, National Institute of Water and Atmospheric Research in the central South Island of New Zealand. Spent a bit of time there with a bunch of American guys doing atmospheric research. They had 3 x 10W lasers of different wavelengths that went vertically up into the atmosphere.
They would measure the reflected energy and spectrum responses to determine absorption of various atmospheric gasses. Much of this had to do with the Ozone hole studies back in the 1990's

cheers
Dave

davenn, May 21, 2012