Safe laser power for DIY spirograph, line and galvo scanner?

Hi!

I'm doing some DIY projects strictly for home use with lasers. I'm planning to make a good spirograph laser "show" and perhaps a galvo scanner at some point in the future, and perhaps a line scanner.

Since I'm basically a noob on lasers, apart from having a few of your typical dollar store pointers, I don't know much about how powerful lasers I need for a good effect. I was planning to start with a typical 5 mW 650 nm red laser such as this one: Ebay Mitsubishi laser

And later upgraded with green:

Green

Would this be safe to use without safety goggles? I'm aware that lasers on ebay could be over-specced and could potentially be a hazard. I don't want it to pose any danger at all for people not wearing goggles, and there won't be any way to stare directly into the laser, will be projected on white ceiling and walls.

Would also like an option for blue laser, but seems to be harder to find low powered 5mW blue laser modules, so I may assume blue is not as safe to use?

Tried to search around, but didn't really find much which applied to my application, but I did find that <3mW was max safe for general pointers.

As long as you stick to <5mW, you or anyone else will be fine to go without safety goggles. Laser pointers must meet Class 2-3R regulations which limit them to 5mW.
Blue is really quite hard to locate for <5mW, and for how much its going to cost, the brightness won't be worth it.
Green for the brightness aspect is the best choice to go for, but it is hard guaranteeing them <5mW. A lot of companies overspec/understate their lasers on purpose.
Can I suggest you put your location of your profile as it makes things a lot easier for suggesting ideas. As you mentioned dollar stores, I take it you are from the US.

Dollar store was just used as a general term, as it's very recognizable for pretty much everyone.

I am Norwegian, but I live in the Philippines. There's not much available locally, so I'm limited to ordering from ebay/aliexpress/bangood or dealextreme. I've saved my location in the profile here.

Initially I was planning to use 10mW lasers for this project, but when going through the parts and reading up I was worried that this might be harmful in a device that shoots the beam everywhere. I've seen videos on youtube using 100mW lasers and such for this, but I can't imagine that's a safe thing to do. It will be projected on to white walls and the ceiling at a distance of about 1-2 meters, I supposed that's around 3-6 feet. I'll be using 2, 3 or 4 dentists mirrors attached to DC motors to create the spirograph, not sure how much loss these mirrors will cause on the beam. I'll be starting with red and green, perhaps using a beam combiner to mix them into one single beam. Blue/violet seems to be a more difficult color to do without going up in power, which might make it unsafe.... This is never gonna see any professional use, it's purely for home DIY usage, perhaps with a fogging machine to expose the beam better.

Is there any way to know if those I linked to are overspecced or indeed correctly specced at 5 mW? The red has a selectable power in the ad, what I will select in those drop down menus is dot/5mW/with adapter and holder

For these I use Maxwell software with my RGB laser projector. Awesome patterns. But it is not what you are asking I guess... Also the projector is far above 5 mW.

Edit: Maxwell SW - Might be usefull for anybody else having similar question.

Pretty cool, I assume that's using a galvo mirror setup?

Will definitely try that next, but will start with a spirograph as that's much simpler.

I guess if you're doing larger patterns and such, you need stronger lasers? Won't venture into any RGB single beam laser yet, as it seems to be a bit expensive. But I guess it's more doable to do a red green and blue separate laser module setup then use a 3-way beam combiner?

But for my opening question, I think I'll stick with 5, perhaps go to 10 mW for now. I am also gonna connect a 555 adjustable pulse circuit to it to make the patterns more interesting. At 5 to 10 mW I think it would be quite safe if mounted in such a way that you can't stare directly into the beam.
My biggest problem I guess is if these ebay sellers are selling correctly specced lasers, at the 20-30 bucks per laser module, that is a really good price for a project.

I tried an m140 in my spirograph pj.. took it camping and projected it on a huge rock wall in the middle of the night.. not safe.. but awesome effect

Skauber said:

Pretty cool, I assume that's using a galvo mirror setup?

Will definitely try that next, but will start with a spirograph as that's much simpler.

I guess if you're doing larger patterns and such, you need stronger lasers? Won't venture into any RGB single beam laser yet, as it seems to be a bit expensive. But I guess it's more doable to do a red green and blue separate laser module setup then use a 3-way beam combiner?

But for my opening question, I think I'll stick with 5, perhaps go to 10 mW for now. I am also gonna connect a 555 adjustable pulse circuit to it to make the patterns more interesting. At 5 to 10 mW I think it would be quite safe if mounted in such a way that you can't stare directly into the beam.
My biggest problem I guess is if these ebay sellers are selling correctly specced lasers, at the 20-30 bucks per laser module, that is a really good price for a project.

Click to expand...

Even with low powers you get nice patterns, but not in longer distances. However it is good for testing your galvos. The projectors use ILDA protocols, not sure if Maxwell could work with custom built "projector". Search forum for related stuff regarding galvos etc. I would be carefull with ebay. Get recommendations here if you wish to use ebay. There are even mini RGB modules ready. Search for ArcticDude's rgb host to see how he used it. He built nice rgb laser and in his other thread he posted nice beamshots with it. It is quite hard to get beams aligned, so maybe this would be solution for you.

And finally - Welcome to the forums and make sure you post in welcome section to introduce yourself- excelent and helpful community is here. Do not forget to study laser safety and spend some time on it. See laserpointersafety.com and safety forum here. And get proper glasses as you are going to work with optics and likely at least class 3B - not eye safe. Consider many low power bellow 5 mW are mislabeled and give more than that, some even to the level, where injury may occur in real conditions.

BTW Rep+ for being safe and to have a good start here.

I see glasses are rated for wavelengths, one set of glasses for green lasers, one for red etc. So, if I'm gonna be working with both red and green, which glasses do I use?

I'm gonna be doing red and green in this project, blue seems to require a bit too much power for my liking. Thinking of going with the 10 mW versions of the focusable laser modules, then I'll experiment with different focus on the beams. Wider beam = safer, right? I'm also gonna pulse the beams. I read that a pulsed beam is safer, as well as giving an interesting variance in the spirograph setup. I've ordered dentists mirrors advertised as front surface mirrors, though I'll be surprised if it really is that. They were 6 bucks for 10, so just had to try. If they're back surface mirrors and give too much glare, I'll shop around for better later, just need something to get this project off the ground. Then I have 12V DC motors rated at 6000 rpm with pwm speed controllers, that should do it for now. Not gonna do a beam combiner lens/mirror yet, but may introduce that later when I have a working "prototype" going.

For pulsing the beam, I'm planning to use an adjustable pwm controller. Do I connect it like (power supply > pwm > driver > laser) or (power supply > driver > pwm > laser)? I find it most logical to wire it between power supply and driver, same as I would with a dimmer for an LED, but not sure if lasers require a different approach. Once I have this working, I'll be introducing an arduino with pwm drivers to run programs and such.

Well, to get you some reference, my projector has beam about 4 mm diameter and 1 mrad divergence (as specs say). I can use it in my room on wall about 3-4 meters far, but not on full power. About a 25 % I feel is good (output about 250 mW). And my room is illuminated quite well. It is RGB - no glasses I'm aware of are able to cover it as you won't see anything.

When I do laserpainting (without projector so far), I usually have one glasses for violet, blue and green and another pair for yellow and red. I have to switch them. But for 10 mW of CW it would be not really difficult to find some - you should get at least OD 1 (if the modules are not overspec too much) - look here. However it is not cheap company - but you can consult with them your requests to get recommendation.

Regarding pulsed beam it depends on many factors - but if you consider just to pulse CW module it reduce the overall visibility as well and under certain conditions it might be more safe. But in general - pulsed lasers are not allowed for audience scanning - very high risk of injury as it might exceed MPE in short pulse - that's why just power of pulsed laser is not sufficient for evaluating of safety. So if you have 1 W CW and 1 W pulsed laser you cannot compare them in calculations of safety stuff without knowing more information about the pulsed laser operation.

Better is to have wider beam to reduce energy density, but it depends on divergence as well. But wider beam might not be that exciting to see. And if you scan beams even this might reduce danger, but at the edges you might get hot spots. There are many methods to ensure MPE is not exceeded.

I think it is good to look here.

But really 10 mW is just a bit stronger than laser pointer - do not expect much widescreen lasershow from it. But might be good to start with. And do not forget if you get laser diode it has to have a special driver, you cannot just connect it directly to source.

Yeah, I bought laser modules which comes with everything to power them, the diode, driver and 5V power adapter to plug in to the wall, and a holder. The pulsed beam I'm thinking of is to create another "dimension" to the pattern, like having the possibility to draw a dotted circle instead of a solid line circle on the wall, I'm presuming since it's a laser diode, I can connect a pwm before the driver just as with any other LED.

As for safety glasses, are cheap glasses on ebay worth buying? Do they actually protect anything? Example: 15.99 usd and 1.99 usd

When I buy lasers, apart from getting a rather expensive laser power meter, are there any way of measuring the laser power, at least get a "ball park" figure from measuring current draw or similar?

You can measure current draw to estimate it in terms of "less than" as there will be some losses and physics laws appply.
Regarding these glasses I have no experience with them, but looking at price and specs they seems as crap. They might be used only on some party as part of costume, not as protection. Try to search for Eagle pair, they were recommended here by many members. I have also a lot of glasses from Wicked Lasers, which are quite good IMO, but they were supplied with my lasers. And I also have T-Rex crap, which I use for burning tests - by burning I mean burning them. T-Rex will not protect your eyes as well as likely those you posted. If you want to be safe invest in quality glasses. Maybe you will not realize you need them untill you know you needed them and did not have them.

Edit: my Evo laser uses pwm look for schematics on WL website.

Ok, thanks. I see Eagle pair are around 40-60 usd, so that's fine. Basically, if I shine the laser through it and the beam can't pass through the lens, then all is good? Or is it not possible to tell if glasses will protect or not without measuring it with lab equipment?

Gonna need glasses when experimenting and building it, specially when aiming the beam at the mirrors.

You are welcome. The beam passes through any glassees, otherwise you could not see it. The role of glasses is to reduce the beam not to exceed MPE under direct hit. Also to add - OD value and wavelength are not only parameters to consider. But for CW laser and your purposes they should be fine.

You need at least LPM to measure beam after filter. But I estimated it by playing with pointer (5 mW) and comparing sensual perception and as I did some tests with higher powers. But these estimates are just for reference not nearly for some values. Human eye is tricky and you cannot say untill you LPM it. Especially at higher powers you cannot even use my highly inaccurate estimate method.

As a cheap beginner protection, would welding goggles protect against low power lasers? I know they don't protect against high powered lasers from what I read, but lets say 10 mW, with a 50% overspec allowance giving a power of 15 mW direct hit?

Not sure with that. I would recommend to stay with eye protection designed for lasers. You cannot put a price tag on your eyes and I assume you will go for higher powers once your project is finished and you relalize that you are limited by low power. So laser glasses are a very good investment IMO.

I might go with more power once I start delving into galvo scanners, but in the spirograph I think 10 mW is about as strong as I want to go, as I believe that is strong enough to give a nice pattern on the wall, and provide a nice beam if I get a fogging machine. Obviously I'm gonna invest in some good laser goggles when that time comes, as I do appreciate my eyes. I used to play with lasers as a teenager, and I'm surprised I didn't damage my eyes back then when I built a HeNe red laser kit, but I think it was about 5mW, not sure. That laser gave a pretty nice beam with a fogging machine, but never got around to making the spirograph for it so this is kind of revisiting that project in a more modern form.