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Controlling Laser module by Arduino

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Hi

I want to build something like this:Fade Away 1 - Matt Richardson, Creative Technologist

Now I wonder 2 things:

Firstly I'm not entirely sure how to control a laser with arduino. I can't find anything really good online. Say I wanted to hook up this laser: 532nm 30mW Green Laser Module 1 PCS | eBay

It has already got a module built in, so could I just hook it up like a dc motor? With + and - connected like in the first picture here: Motors 1





2) My second question is: How much power do you think I need. I would like to keep it as low as possible for safety reasons. Would 5 mw do the trick or do I have to go to around 30?

Thanks in advance

PS: I hope this is the right subform
 
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diachi

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Are you trying to replicate the same machine you posted exactly? If so - a green module won't work, you'd want a 405nm module. It looks like you'd also need one with a driver that supports at least TTL modulation, doesn't hurt to go for analogue, that way you can turn the laser on and off to create spaces in the text.
 
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Yes I am trying to replicate that machine. Why do you say it wouldn't work? Does the phosphorescent plate not react to that frequency, or do you simply mean the machine will look differently because of the different color?


. It looks like you'd also need one with a driver that supports at least TTL modulation, doesn't hurt to go for analogue, that way you can turn the laser on and off to create spaces in the text.
My schematic would have allowed that... I think. Basically I am asking this: If I connect + and - of the Laser directly to a 3 v power supply, would It work (and not break)? If yes, then you could simply disconnect and reconnect the power supply via a transistor connected to the micro controller. Is that correct or do I need additional circuits?
 

diachi

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Yes I am trying to replicate that machine. Why do you say it wouldn't work? Does the phosphorescent plate not react to that frequency, or do you simply mean the machine will look differently because of the different color?




My schematic would have allowed that... I think. Basically I am asking this: If I connect + and - of the Laser directly to a 3 v power supply, would It work (and not break)? If yes, then you could simply disconnect and reconnect the power supply via a transistor connected to the micro controller. Is that correct or do I need additional circuits?
Yes, the phosphorescent plate won't react to 532nm, at least not noticeably. The original creator used 405nm for that reason. He says "ultra-violet" on his site, but it's not quite UV - it's near UV, either way, that's the wavelength to go for.

Assuming the module needs 3V, then yes, you can connect it like that.

You could turn it on and off that way, as long as you're not going too fast - I wouldn't trust the cheap drivers on those modules to produce a clean output when you rapidly turn the power on and off though. The best way to do it is to use a driver that supports modulation, that way you provide a constant source of power to the driver and turn the laser on and off using a separate modulation signal - provided by your microcontroller. Generally you'd be able to modulate up to a few 10s of KHz, so going with the modulation option opens up some options for what you can do - especially if you go with analogue modulation.

A module/driver with modulation isn't something you'd need to build - you can buy them ready to go.

This one has TTL modulation (On and off only!): NEW 12VDC 405nm 150mW Blue Violet Laser Diode Module With 0 20kHz TTL Modulation | eBay

It also takes a 12V supply which is a little more standard than 3V. 150mW is more than enough power - and you could in fact go with something lower if you want to be safe, 150mW is well above the threshold for eye damage due to direct exposure to the beam.
 
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Thanks for your answer. Believe it or not, but you are actually the first one who has been able to help me. Thanks!

I am quite new with lasers (who wold have guessed that). I wonder how come laser diodes can not be connected directly to a voltage and current regulated power source similarly like an LED? What is the reason?


This one has TTL modulation (On and off only!)
Thanks for your suggestion, but I think its a bit to fancy for my purpose. I will not even be switching it on or off more than twice a second.


Yes, the phosphorescent plate won't react to 532nm, at least not noticeably.
So I guess I'll have to find a different laser... If I use a different phosphorescent plat (still a green one) how do I know what frequency to use? Always 405nm?
 
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diachi

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Thanks for your answer. Believe it or not, but you are actually the first one who has been able to help me. Thanks!

I am quite new with lasers (who wold have guessed that). I wonder how come laser diodes can not be connected directly to a voltage and current regulated power source similarly like an LED? What is the reason?




Thanks for your suggestion, but I think its a bit to fancy for my purpose. I will not even be switching it on or off more than twice a second.




So I guess I'll have to find a different laser... If I use a different phosphorescent plat (still a green one) how do I know what frequency to use? Always 532nm?

This is why you need a constant current driver for a laser diode:

You certainly can hook up a lab power supply to a laser diode and provide a voltage and current to the diode, but you will be operating it as a voltage controlled source. With providing a constant voltage instead of a constant current you have the possibility of having a “run away” situation in which the current will increase and the voltage will stay constant. If you keep the voltage constant across the diode, then as it heats up the current will increase. As the current increases, the laser diode will heat up more, which in turn creates more current. This process, if left on its own will eventually destroy the laser diode.
You also generally want a nice clean constant current source, laser diodes are rather sensitive to ESD and unclean current sources.

As for your phosphorescent plate, if you want to stick with a green plate then you can't use a green laser (typically 532nm). The process works by absorbing a higher energy photon (blue/violet) and releasing a lower energy photon (Green in this case). A green laser might work with a red (Red being lower energy than green!) phosphorescent material, but I haven't tried it so I have no idea how well it'd work. Violet (405nm) would work in either case just fine.
 
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What sort of power would I be looking at? You see I want to run the machine as a clock, so that It would write the current time every ten minutes or so. That is why I would like to use as weak a laser as possible so that you do not have to wear eye protection, and there is no risk of fire or so...
 

diachi

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What sort of power would I be looking at? You see I want to run the machine as a clock, so that It would write the current time every ten minutes or so. That is why I would like to use as weak a laser as possible so that you do not have to wear eye protection, and there is no risk of fire or so...
You'd want to stick to a 5mW laser in that case. :) That said, you need to be careful where you order from - a lot of lasers are advertised as 5mW but can be anywhere as high as 100mW or so. May be worth having someone verify the power if you're worried, although realistically you don't need to worry about 100mW as long as you don't take a direct or reflected (Off of a mirror or some such) hit to the eye. It's not going to cause a fire either. Common sense is enough at that sort of power.

Maybe see if someone can put something together for you that is actually 5mW, that way you know you're safe.
 
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I noticed the guy used a "UV" laser . You could not see the beam in the dark so that gives me an upper power limit. From what power onward can you see the beam in the dark? Are you sure 5 mw is enough power for this project?

Also i found a laser module that seems perfect of me:Adjustable 5-20mW Brass 405nm Module with 3v Boost Driver (12mm) - OdicForce

Some questions do still arise to me...

1) The reason I like this module is because you can change the power of it (5-20 mw). However It does not say how to adjust the power... How do you adjust it?

2) What voltage do I use? Again the description does not say anything

3) Do I need to buy a separate lens? It looks like there's no lens on the picture, but in the description it says: "Dot pattern beam", so is there a lens or not?
 

Atomicrox

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I think that module will work fine if you pulse it with a transistor. It says there it's 3V powered. You adjust the current by using a tiny screwdriver on the small pot on the driver board, taking care not to break it. No need to buy a lens.

I have one of those glow in the dark sheets and it works with many wavelengths but 405nm is by far the best.
 
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Ok thanks!! I think I almost know everything I need to know now.

So If I run It with 5 mw, is It safe to use it as a "clock", leaving it on all day with people walking by wearing no safety goggles? I would probably build a box around the laser with only the side facing the glow in the dark sheet left open. The dot isn't dangerous right? I'm thinking about sand-papering the sheet to make it less reflective... But maybe I'm just over careful :D

Another thing I wonder, is it possible to reduce the watts the laser runs on by adding a resistor?

How sensitive are those sheets actually? For legal reasons it might be easiest to use a 1 mw laser, but that might maybe be to weak?
 
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Ok thanks!! I think I almost know everything I need to know now.

So If I run It with 5 mw, is It safe to use it as a "clock", leaving it on all day with people walking by wearing no safety goggles? I would probably build a box around the laser with only the side facing the glow in the dark sheet left open. The dot isn't dangerous right? I'm thinking about sand-papering the sheet to make it less reflective... But maybe I'm just over careful :D

Another thing I wonder, is it possible to reduce the watts the laser runs on by adding a resistor?

How sensitive are those sheets actually? For legal reasons it might be easiest to use a 1 mw laser, but that might maybe be to weak?
well, if there is going to be very little chance of the laser beam going directly into someones eye, then its definitely ok to have more power. its hard to get a true <5mW laser, so don't bother trying to find one and just go for a higher power diode (~30mW should be easy to find, and suit the application well).

generally you don't use a resistor, you use a driver that outputs a lower current to the diode.

if its just going to being your home and not being mass produced or put in a public place, then there are no legal issues (assuming you live in the US). you could use a 1000mW beast if you wanted to, and it would be perfectly legal and very dangerous.
 
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I live in Switzerland so the legal situation is a bit more complicated...

its hard to get a true <5mW laser, so don't bother trying to find one and just go for a higher power diode (~30mW should be easy to find, and suit the application well).
I'm probably going for the 5-20 mW one I linked before. I know its hard to find a 5 mW (because I didn't :D) so thats why I had the Idea with the resistor: I meant you use a driver, but in front of the driver you put a resistor that limits the current even more. Would that work?
 

Atomicrox

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It wouldn't work, unless the driver is crap.

The sheet is sensitive enough to write with my 30mW 405nm pen, and that's the weakest one I have. I suppose 1mW is too weak, but it's a guess. The fluorescent green dot looks bright but isn't dangerous. It does reflect a good deal of laser light. What I'd do is glue it on a hard background and place it on a position such that neither the original beam nor the reflection can hit anyone on the room. Shouldn't be too hard.
 
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What I'd do is glue it on a hard background and place it on a position such that neither the original beam nor the reflection can hit anyone on the room.
I'm not sure how I'd do that... I mean If a person looks at the board, it he would stand directly in the line of fire of the reflection... Like in this picture: https://cnx.org/resources/26870a12b47ef00ee97b3d5469a3684bc8ccc4b9/Figure%2026_02_06.jpg

That's why I thought you might be able to make the sheet matt by sand papering It.
 




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