1000mw LASER diode driver

Thread Starter

yourminky

Joined May 31, 2019
28
I need a very basic power source to drive a 1000mw LASER diode. What are the typical forwarding voltage and current requirements for a generic 1watt LASER? Can I use a 5volt 1amp phone charger and add a power limiting resistor and a capacitor to drive it or do I need a 12volt power supply and a LM317 regulator?
Advanced thanks for your comments.
 

Dodgydave

Joined Jun 22, 2012
8,797
You can use a 12V supply wih a LM317 in Constant Current mode better, then you don't need a Series resistor, just a preset to set the current limit/brightness.

The specs will be listed on your laser voltage and current etc..

Like this circuit, current is 1.25/R, so from 125mA to 11mA..


Laser-Diode-Images-8.jpg
 
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Thread Starter

yourminky

Joined May 31, 2019
28
You can use a 12V supply wih a LM317 in Constant Current mode better, then you don't need a Series resistor, just a preset to set the current limit/brightness.

The specs will be listed on your laser voltage and current etc..

Like this circuit, current is 1.25/R, so from 125mA to 11mA..


View attachment 191986
Thanks for the schematic. I only have a 5volt 2amp USB phone charger and a 12volt 7amp laptop power supply and a 18volt 6amp laptop power supply to use with this. Will this circuit work with any one of those power supplies? Is the 100ohm resistor 1 or 2 watt?
 

Dodgydave

Joined Jun 22, 2012
8,797
Any voltage upto 35V will do, the resistor is rated at the maximum current so that's 1.5W, I would use a 3w or use a transistor buffer.
 

ericgibbs

Joined Jan 29, 2010
9,531
hi,
I would strongly recommend that you determine the type number of the laser diode. BEFORE applying any drive current.
We can then can give you the correct guidance.

The light output may be invisible to the human eye but it it is still capable of causing damage.

E
 

bertus

Joined Apr 5, 2008
20,317
Hello,

The light output may be invisible to the human eye but it it is still capable of causing damage.
From the page I posted :

Comments on Eye Protection for High Power Lasers
(From: Paul M. Brinegar, II (montyb@pulsar.hsc.edu).)
I would have to say that proper eye protection is much more important than any laser component. This cannot be stressed enough. There have been some interesting demonstrations performed showing the effects of high optical power densities on meat (think lots of smoke and some flame). The ones I've seen on videotape were spectacular, and were more than enough to convince me that proper beam blocks and eye/body protection are mandatory.
When in doubt, be overly safe.
You should have enough pairs of laser goggles for everyone in your laser lab! After all, what's the fun of a laser if you can't show it off to your friends?

Now, about the ratings of goggles in terms of optical density.
Optical densities are reasonably easy to understand. To determine the fraction of optical power transmitted through a material of optical density D, divide 1 by 10 raised to the D power. Or, if D is an integer, just write a zero followed by a decimal point, followed by D-1 more zeros, followed by a 1. This is the fractional transmittance of the material. Multiply by 100 if you want a percentage.
For our O.D. 5+ goggles above, this means that less than 1/100,000 of the incident power will pass through the goggles, the remainder either being reflected or absorbed. For a 100 Watt laser with a 1 square centimeter beam (power density 100 W/cm2), the transmitted power density should be 0.001 W/cm2 (or 1 milliwatt per square centimeter). I have to locate my safety sheets to see what the exposure limit is for eyes and skin under a 1 mW/cm2 beam at 10.6 microns. I suspect it is eye and skin safe, but without a good reference, I'm not betting my body parts on it.

Keep in mind that the O.D. is rated AT A SPECIFIC WAVELENGTH OR RANGE OF WAVELENGTHS! Deviations from this wavelength will results in completely different O.D. values. If the goggles use some type of interference coatings, then at some wavelengths the coatings may have an effective O.D. of ZERO, meaning they are completely transmissive. Don't expect CO2 goggles to protect you from an argon laser beam.

You only got one pair of eyes, so play safe at all times.

Bertus
 

kubeek

Joined Sep 20, 2005
5,675
That thing may consume 1W but would only produce 20-50mw of optical output. And I seriously doubt the 1000mw figure, more like 300mw due to needed heatsinking.
 

Thread Starter

yourminky

Joined May 31, 2019
28
Thanks for the safety tips. I am well aware of the danger and always use proper eye and skin protection. No more safety tips please.
This LASER diode came from a NEJE wood engraver. I am sure it is a Chinese NEJE 1watt LASER. Link to the engraver is below. The laser attaches to this engraver.
https://www.amazon.com/Engraver-1000mW-490x490-Engraving-Machine/dp/B07XQHGG6MAs far as I know this laser runs on 3.7v to 5v. Can I simply plugin a 5v 1amp USB power supply directly to the laser without using a limiter like LM317?
 
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Alec_t

Joined Sep 17, 2013
10,900
Can I simply plugin a 5v 1amp USB power supply directly to the laser without using a limiter like LM317?
Most unlikely, but wthout the full spec of the diode it's impossible to be sure. At the very least I suspect you'd need some current limiting arrangement.
 

Thread Starter

yourminky

Joined May 31, 2019
28
Most unlikely, but wthout the full spec of the diode it's impossible to be sure. At the very least I suspect you'd need some current limiting arrangement.
Found the specs for the laser diode.
Neje 1000 Milli Watt laser model CG20794A 1
5 Volt, 1 amp
405 nano meter wavelength violet laser
 

TeeKay6

Joined Apr 20, 2019
572
Found the specs for the laser diode.
Neje 1000 Milli Watt laser model CG20794A 1
5 Volt, 1 amp
405 nano meter wavelength violet laser
@yourminky
If you apply 5V directly to the laser, you have no control over how much current will flow. A small change in voltage can produce a large change in current. In addition, the appropriate drive voltage is temperature dependent. Ideally you would control current dependent on temperature of the laser diode (not the ambient temperature). Some lasers incorporate an ordinary silicon diode to use as a temperature sensor. There are many laser drive schematics online; take a look at some of them to see how others have solved the problem.
 
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