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Laser glow in the dark clock

jjsym

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Hello to all laser pros out there. Im working on a project where I will use glow in the dark material and blue/uv laser to draw current time on the material every minute. It will work as a night clock during dark hours at the bedroom.

Idea is that Ill stick the glow material to a wall where I want the clock and then have the drawing module at different wall doing the drawing across the room with laser. Software compensates the geometry so it can draw from weird angles too.

It seemd simple project to do but Ive run into a few issues.

I have glow in the dark material, laser, servos etc working quite OK.

Biggest problem is the noise of servos. As many of you know, as I move the laser with servos to create the number figure it makes noise... and thats bad in a quiet bedroom. Here is where Im asking for your ideas.

What are some silent ways of modifying the laser beam direction accurately? What methods are even available?
I know there are these filters that make figures on the wall.. can I make those myself for every number and rotate them? How do they work?

All ideas are welcome, thanks!
 
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paul1598419

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Why do you need a laser to have a clock you can see in the dark? I have a cheap digital CD player/alarm clock that does this quite well and very quietly too. Some things were never meant to be done with lasers. I think this is one of those.
 

Cyparagon

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Oh give it a rest, Paul. MOST of the shit done on this forum has no real purpose. Why would you want a multiwatt handheld laser? For many of the same reasons you might want to build something like this clock. It's quirky, it looks cool, it's a challenge, it furthers your knowledge of electronics, it "sounds badass", and it's fun. Let other people enjoy things.

It's one thing to say "I am looking for the best way to tell the time in the dark", but clearly this isn't OP's goal, as even the most fierce of idiots would be aware of radio alarm clocks.

Mr. sym, look into laser show galvos (short for galvanometers). These are relatively quiet at full speed, but are practically silent if driven slowly. They're not all that cheap, but they're fun devices to experiment with, and you can rebuild your device into a laser show projector when you get tired of the clock.
 
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Gazen

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As already stated, this is an impractical project, but then again, most projects on this forum are. As Cyparagon said, a galvo could work, which utilizes mirrors to guide the beam.

Your best bet for the laser is 405. There are no uv diodes atm at a reasonable price. Unless you get lucky and find one on the surplus market, their cost will be in the thousands. Keep in mind duty cycle or you may wake up with a dead diode.

Good luck on your project
 
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Benm

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Well yeah, the galvo's drawing the clock face would produce noise, there is no way around that really.

But perhaps there is another solution to it: You have these alarm clocks that project the time onto the ceiling or wall, usually using a red LED as the source of light. Under daylight conditions this is hardly visible at all, but at night it's quite pleasant: legible if you look at it, but not bright enough to distrub your sleep.

You could replace the red LED in such a device with a 400nm-ish one (or blu-ray laser diode without a focussing lens) and then paint the target area with fluorescent paint. I'm not sure what the result would look like, but it seems feasible to try.

These things usually display the time in numbers like 12:34 rather than a clock face, but it would be a start ;)
 

ArcticDude

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jjsym

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Galvos seem like a solution that might work. Atleast the principle behind them seem way more silent than servos. Anyone have experience how silent are they?
For sure they make some noise but if I fill the drawing unit with acoustic material and only have a small hole for light to make it out it might be enough...
Could also have a glass to even further work as sound proofing.

Galvos seem great for other future projects too and theres some going for ~70€ on ebay.
I'll try one of those and see how it goes.

Thanks!

Edit: That MEMS thing seems awesome, but probably way overkill as it's meant for LiDAR and other high precision technologies.. found one listing on ebay:
https://www.ebay.com/itm/5mm-MEMS-F...-Micromirror-by-Mirrorcle-2-Pack/323320970058

"List price at manufacturer, Mirrorcle Technologies is: $936.00
Offered at 70% DISCOUNT due to overstock.

Note: SOLD IN PACKS OF 2
Buy now for only $649.00"
 
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Cyparagon

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Anyone have experience how silent are they?
In regular (projector) use, there's a slight buzz/hum/tone that changes depending on the projected image. Most/all the noise is created from the moving mirrors acting as teeny speakers. However, if you slow the drive signal way down, they are silent. There's no need to retrace GITD material at tens of hertz for persistence of vision, since the GITD material itself provides the persistence.
 
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paul1598419

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These 2D MEMS scanning modules are very cutting edge, but they are priced like it too. I imagine these could be used to scan all sorts of 2D things, but there has to be a cheaper option for people who don't have an unlimited budget.
 
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Benm

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In regular (projector) use, there's a slight buzz/hum/tone that changes depending on the projected image. Most/all the noise is created from the moving mirrors acting as teeny speakers. However, if you slow the drive signal way down, they are silent. There's no need to retrace GITD material at tens of hertz for persistence of vision, since the GITD material itself provides the persistence.
That's a fair point - i'm used to galvo's running at fairly high speeds (at least 20.000 pps) but there would be no need to move fast with the GITD paint.

It would be mostly a matter of getting sofware to drive the galvo's that slowly as most controllers are designed to run at projector speeds, and also keep the mirrors in position as best as they can, compensating for overshoot and things like that.

There would be no reason they could not handle slowly changing signals though, producing far less noise. You could essentially slow them down to a crawl or 50 pps or so and just draw in the clock lines without making any hard/fast turns which usually cause a lot of noise.

Compare how loud is it is to draw an unoptimized 'starfield' simulation versus just a circle with a regular scanner.
 

kecked

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LCD gobo

The 405 glows a very bright blue when it hits the green phos. It will wake you up. I gurrenttee it.
The scanner will make noise as well. Yes you could turn the laser down in brightness.

You could also make the 8segments out of a diode laser and cyl lens to spread it out. Now you just drive the laser like the regular digits. No scanner needed. Use cheap 660nm diodes as you would need 30 diodes. Less if you are clever and use shutters.
 

Cyparagon

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sofware ... also keep the mirrors in position as best as they can, compensating for overshoot and things like that.
No. The stability is done with hardware on the amp board via trimpots. I've personally aligned/calibrated scanners before. A delicate balance between gain, low frequency damping, and high frequency damping determines the "overshoot and things like that". If the amp board is aligned properly, the mirror position is linearly proportional to the input voltage. No "software" required. Any bog-standard signal generator will suffice.
 

Benm

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This is indeed usually done with trimmers on the galvo driver boards, which can be a big pain to adjust too since they all influence each other to some degree, so you can be fidding with them for quite some time even if you know what they actually do.

But there is a software side to it as well: If you want to scan a certain pattern it helps if you do it in an efficient way. If you wanted to project something like a circle for example, you could do that by moving the mirrors around smoothly along that circle.

You could also do it by scanning it line by line like a CRT TV would, or as dots on it's edge in a random order.

The latter may seem pretty idiotic to do, but when images get more complex it does actually matter what order you scan things in to minimize large sudden deflections if possible.

The test patterns are designed to make the worst case results and to see how a system then holds up. Sometimes you can get a pretty terrible standard ilda test panel, but a laser show that looks perfectly fine if you're just scanning circles and lines at a moderate rate (like disco lights, not proper image projection).
 




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