# Class 3a laser safety

#### k1ng 1337

Joined Sep 11, 2020
687
Hola,

I have the laser seen below and have reviewed the associated guidelines and classifications. Since the supplier has not yet supplied the datasheet, I wanted to confirm the module is safe to use for my nefarious purposes.

At the rated voltage, power is around 125mW. This agrees with Optical Power vs Forward Current graphs suggesting a 5mW laser with a class 3a rating. Charts indicate this power level is unlikely to start a fire which is the main concern.

The project includes a laser beam that is always moving. The beam may be passed through filters, reflected / scattered by minerals or machined metals and focused on a wall directly.

Aside from general use, I also would like to explore the possibility of accidentally focusing the beam instead of spreading it out (please forgive the terminology) by means of a concave surface or the like.

Specifications
Class IIIa laser diode module
650nm (red) dot output
6mm diameter (0.235″) x 13.9mm (0.55″) overall length
Dot spread at 15M distance measures 10-15mm diameter
5VDC maximum input
-36 ~ 65°C operating temperature range
Prewired with 75mm (3″) wire
1.4g

#### Tonyr1084

Joined Sep 24, 2015
7,098
safe to use for my nefarious purposes.
Depends on what you mean by "Nefarious purposes". If you intend harm - I can't support you on that.

I happen to have a bunch of these lasers. My intent has been for many years to build a rig with a rotating mirror that will cast the beam on a wall in a circular motion. That beam is then pulsed to the amplitude of music. Given that it is a DC device, when the waveform goes negative the laser extinguishes and reappears when it goes positive. The affect is what appears to be dots or dashes on the wall that can be stationary or rotate in either direction depending on the RPM of the mirror and the frequency of the musical note being played. I've built mechanical versions of this before and the affect is impressive. You can also have dots and dashes moving in both directions at the same time all from a single beam rotating around in a circular fashion.

and yes, mine are 5mW red lasers. The housing is focusable, and I had to tweak some of the modules to get the point as small as possible. I would imagine that at greater lengths the focal point would need further adjusting.

Hope "Nefarious" doesn't mean harmful.

#### k1ng 1337

Joined Sep 11, 2020
687
Thanks. I know. Which is why I said I can't support his intentions if he plans on harming living things or property.
I'm vegan, I do not tolerate the harming of anything! The nefarious bit was just a joke, of poor taste in retrospect..

#### DickCappels

Joined Aug 21, 2008
9,320
That looks like the red laser diode assemblies I bought via eBay for about U.S. $0.30 each. The electrical power you report is about the same as the ones I have. Optical power is pretty low , I would guess a couple mw or less, and having a long wavelength they don’t make me nervous, but it is a laser, so just don’t point it into eyes and you should be ok, By the way somebody here mentioned that driving them with 5 volts results in a short operating life, and they lasted longer with a lower voltage. #### Ya’akov Joined Jan 27, 2019 6,575 For the record, I am very confident the TS was using the word “nefarious“ in a humorous way. Some words are very rarely used in modern speech except for humorous effect, particularly Latinisms (see: tonsorial arts, for example). The intended effect of the word here is to invoke a common humorous style of self-deprication, the idea being that the writer is somehow a bad person and so whatever they want to do is nefarious. Self-deprivation is a very American form of humor, though not exclusively. In any case, I don’t think there’s any chance of the TS intending to reveal his intentions of doing harm with lasers, and in fact his concern with safety and what explanation he did include strongly belie the “nefarious” label. On the question itself, as much as those who do have nefarious intent would love the idea that they could start a fire with a laser that costs a few cents, there‘s not a chance on the planet a fire could be started with the amount of energy that module can radiate. But, as @DickCappels pointed out, while fire is not an issue eye safety is! In this case reflected light is not a concern but direct light in the eyes could be. Though it is very unlikely that laser could do eye damage, it is possible so precautions against it should be taken. Thread Starter #### k1ng 1337 Joined Sep 11, 2020 687 I'll take a moment to reassure everyone that what I am doing is for visual entertainment and proximity detection only. I made this topic because one of my specialties is worrying about stuff such as burning the house down. Depends on what you mean by "Nefarious purposes". If you intend harm - I can't support you on that. I happen to have a bunch of these lasers. My intent has been for many years to build a rig with a rotating mirror that will cast the beam on a wall in a circular motion. That beam is then pulsed to the amplitude of music. Given that it is a DC device, when the waveform goes negative the laser extinguishes and reappears when it goes positive. The affect is what appears to be dots or dashes on the wall that can be stationary or rotate in either direction depending on the RPM of the mirror and the frequency of the musical note being played. I've built mechanical versions of this before and the affect is impressive. You can also have dots and dashes moving in both directions at the same time all from a single beam rotating around in a circular fashion. and yes, mine are 5mW red lasers. The housing is focusable, and I had to tweak some of the modules to get the point as small as possible. I would imagine that at greater lengths the focal point would need further adjusting. Hope "Nefarious" doesn't mean harmful. I have been experimenting with different materials and the effects are very cool. I had this idea as a kid to set up many mirrors in a sort of perpetual motion machine (the thinking at the time) whereby visible light rays are spread evenly throughout the room instead of being absorbed at the 'target area'. I am curious to see how many 'stages' (changes to the laser beam) can be made before it is visually undetectable. I am fascinated with prisms as well. I plan to get some glass to carve groves and surfaces. You could say I am into abstract electrical (and chemical) art where a mathematical expression is 'brought to life' visually. That looks like the red laser diode assemblies I bought via eBay for about U.S.$0.30 each.

The electrical power you report is about the same as the ones I have. Optical power is pretty low , I would guess a couple mw or less, and having a long wavelength they don’t make me nervous, but it is a laser, so just don’t point it into eyes and you should be ok,

By the way somebody here mentioned that driving them with 5 volts results in a short operating life, and they lasted longer with a lower voltage.
I paid 3 bucks for mine, looks like they took me for a ride! I did notice it gets warm at 5V and less so at 4V.

For the record, I am very confident the TS was using the word “nefarious“ in a humorous way. Some words are very rarely used in modern speech except for humorous effect, particularly Latinisms (see: tonsorial arts, for example).

The intended effect of the word here is to invoke a common humorous style of self-deprication, the idea being that the writer is somehow a bad person and so whatever they want to do is nefarious. Self-deprivation is a very American form of humor, though not exclusively.

In any case, I don’t think there’s any chance of the TS intending to reveal his intentions of doing harm with lasers, and in fact his concern with safety and what explanation he did include strongly belie the “nefarious” label.

On the question itself, as much as those who do have nefarious intent would love the idea that they could start a fire with a laser that costs a few cents, there‘s not a chance on the planet a fire could be started with the amount of energy that module can radiate.

But, as @DickCappels pointed out, while fire is not an issue eye safety is! In this case reflected light is not a concern but direct light in the eyes could be. Though it is very unlikely that laser could do eye damage, it is possible so precautions against it should be taken.
An accurate linguistic analysis. You are correct in that the intent was to convey humour. If I was 'up to no good', I don't think it would be a good idea to tell everyone about it. Plus, I used the words "safe to use" in the same sentence as if the two expressions cancel out. I have a cheesy sense of humour and enjoy my wordplay. It is refreshing that a random person would take issue with a single word because there really are nefarious people out there. We had a discussion about using the proper words to express oneself and this topic is a humbling example of that. It was definitely in poor taste to include a word that by definition does not reflect my intentions in a technical setting.

I had a boss who liked to say: "It's not what you say, it's how you say it". I was always discombobulated by this statement because I could whisper "elephant" or I could shout "elephant" but its still "elephant". Maybe what he meant was something like 'It's not what you say, it's how it's interpreted'..

#### Ya’akov

Joined Jan 27, 2019
6,575
I had a boss who liked to say: "It's not what you say, its how you say it". I was always discombobulated by this statement because I could whisper "elephant" or I could shout "elephant" but its still "elephant". Maybe what he meant was something like 'It's not what you say, its how it's interpreted'..
Definitely drifting off-topic here, but...

I think he meant it's not the meaning of something that's a concern it's the emotional content the words bring. That is, it's not denotation you have to be concerned about, it's the connotation you will bite you in the... posterior.

#### k1ng 1337

Joined Sep 11, 2020
687
Definitely drifting off-topic here, but...

I think he meant it's not the meaning of something that's a concern it's the emotional content the words bring. That is, it's not denotation you have to be concerned about, it's the connotation you will bite you in the... posterior.
If that's the case, then I'm doomed either way as I'm not an emotional person. In the sense I can't expect Tony (to no fault of his own) to have the same sense of humour as myself, I can't expect to be in tune with everyone's emotional state. The best thing to do is use exact words. If a person misinterprets common English, I shouldn't be responsible for their irrational emotional state that follows. Human interaction is quite the subject. I wonder what ET thinks of us.

#### Tonyr1084

Joined Sep 24, 2015
7,098
In the sense I can't expect Tony (to no fault of his own) to have the same sense of humour as myself, I can't expect to be in tune with everyone's emotional state.
First, this doesn't hurt me. Sometimes I miss subtle humor. My wife and I are always jabbing at each other all in fun and never a hurt feeling over it. And yet, sometimes she says something that skips right off my shiny scalp. They say grass doesn't grow on a busy street, which I've said many times before until a woman I worked with said "Yeah! And it doesn't grow on concrete either". Oh how we all laughed long and hard at that one. She was quick with a quip but never mean or hurtful.

There's virtually nobody on this website I don't like. I'd be interested in a video of your project when finished.