Seeking advice about parameters for small, DIY backyard laser projector

Hey all!

I am looking to put together a small, backyard laser projection show and I'm looking for some advice about safety and how I should go about creating this.
I am a pretty experienced DIYer and enjoy getting really deep down into the implementation details when I make something. I've been making sounds-reactive installation art with LEDs and am pretty experienced in electronics. It seemed natural to follow a long-time curiosity of mine and combine this installation art with a laser projection system.
While I am pretty comfortable with the electronic construction of the system, I am pretty unfamiliar with laser safety and wish to get advice about making sure that my installation is safe. I know that treating these lasers like loaded guns that can spew bullets everywhere is a good first step, but what I would love to know is:

• For a small backyard system that has a projection surface of say 10'x10', what's a good wattage of laser to use? (Was hoping to find one of the RGB laser units on eBay).
  
  
  
• I know working with the laser to always wear safety glasses rated for all the wavelengths, but how should go about setting up a backyard such that there is a safe viewing area, and the projection surface is easily visible?
  
  
  
• And finally, what would you recommend for that projection surface? I assume that higher reflectivity is not good for safety. What is a good surface to give great images without being harmful?
  
  

Thanks so much for any advice you can lend!

I am also a "backyard" laserist, but not a pro by any means.

I have used two projectors, a 500mW and a 2W. 500mW is not bright enough, and 2W is more than bright enough (but not too bright). I don't recommend buying from ebay. You will do best with an analog laser. Maybe something like the ClubMax 2000, pricey but built well. What software are you planning on using to control the laser?

From what I've read, the general consensus seems to be that screen material should be grey. I have used a cream colored paint tarp and a king size grey sheet. I think the sheet looks better if you're closer, but from 30-40 feet away there's no real difference. More light goes through the sheet, so be mindful of that. I hang the sheet from the gutter of my second story roof.

I have my projector placed in the back on a speaker stand well above anyone's head, and I make the lowest point of the projected laser beam above heads as well. There are formal rules for this if you are doing a professional show (i.e. taking money for the show).

Thanks for the quick reply! Yeah, this is great info and exactly what I was looking for. Here's where the ignorance of not working with lasers before is going to show: what's the reason you recommend an analog laser? I just don't actually know the differences other than their construction. The ClubMax 2000 looks sweet though. The reason I wanted to go with something on eBay (or similar site really) was actually to get the constituent parts and build the laser projector myself (well, within reason, ie, buying the laser unit and galvanometers separately).

My plan is to actually use an ILDA interface to program real time/sound reactive images. I have some great experience writing the algorithms to do this with addressable LEDs (example: https://www.instagram.com/p/BRXmayZj...whatcolorwasit) and figured that it would be quite the show to translate the sound movement directly into the shapes on a laser. Especially with how quick and responsive it is to the music.

And thanks for the tips of using a gray sheet. Now to figure out the best orientation in my space!

Analog simply means that you will have infinite control over colors as opposed to TTL which will only give you seven colors. With TTL, the laser is either fully on or fully off so, you get the 3 primary colors of red, green and blue and the three secondary colors of cyan, magenta and yellow plus white. With analog, since you can ramp up and down the intensity of the laser, it gives you a greatly increased color palette.
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As far as building the laser yourself, that's encouraged here just from the standpoint of learning about them so, kudos to you for wanting to do that. It used to be more of a necessity for hobbyists because of price but, you're now able to buy excellent projectors so inexpensively that many have simply gone that route instead.

Ah, interesting! I had just assumed that the TTL lasers could handle something like PWM like LEDs do, but I wasn't able to find a definitive answer. Thanks. Looks like I will look into analog ones even if just so that I can cap the top brightness lower than full if I don't need all of it to look nice.

Would you happen to know the best places to start looking for the component pieces of the lasers to purchase that aren't eBay?

Welcome to PL, Ryan.

From prior posts here is some guidance on what parts you need and where to find them:

Basic Parts:

Case: Build or buy. If you build, you need optical plate (alum 5-10mm+ thick, longer or wider needs to be thicker for stability. You'll likely want risers to raise the optical plate above the bottom of the case. Power switch, ILDA connectors (male and female), power cord connector, power wire (e.g. 18 gauge), serial cable female and male connections if you want to wire a kill switch, key switch (optional for personal use), case alum (quality sheet alum 1.5-3mm thick), aperture window (optional), aperture cover (optional), fans with covers/filters, rubber feet, L alum to connect outer case components, screws, power and modulation wiring (22-28 gauge), solder, heat-shrink insulation, mounting bracket (optional).

Power supplies: one +24/-24V switching PSU 1-4 amps per channel or alternatively two +24V PSUs, PSUs for any diodes modules that you are building yourself and fan PSU (or share with diode PSUs).

Lasers: Complete laser modules for R,G & B and/or Diodes, diode mounts, thermal compound, colimation lenses, (correction (cylindrical and/or prism) lenses, lens mounts if multimode), pbs cube(s) if combining, diode drivers, connectors, spacial filtering equip if necessary (razors, spare alum, magnets, etc.)

Laser combining materials: Dichros (varies depending on order or RGB layout), dichro mounts.

Bounce Mirror and steering mirrors (varies based on design)

Scanners: Galvos and amps, associated cables

Misc: Facial tissue (for tears), paper towels, 3-in-1 oil, drill bits, taps (including spares), mounting screws, electrical connectors / interconnects, power cord, ILDA cable

Tools: (minimally) drill press, hand drill, jigsaw with metal blades, hand saw with metal blade, metal files (variety), ruler, marking pens, wire brush, rotary tool / dremmel can be used as an alternative for some of the above, electrical meter, laser power meter (optional), hex tool, screwdrivers.

Suppliers:

Drivers: My current favorite for my needs are from PL member BBE's (x-wossee on Ebay): https://www.ebay.com/itm/500mA-analo...wAAOSw~y9ZLbpg or https://www.ebay.com/itm/5A-analog-l...sAAOSwKytZGaRz depending on the diode you are driving.

Diodes & Colimation Lenses: DTR is my top choice for diodes. https://sites.google.com/site/dtrlpf/home/diodes

Dichros and Diode Mounts: Dave at LasershowParts is my top pick.

Cases: Ebay for very small cases or http://goldenstarlaser.com/ for larger cases.

Galvos: Pangolin for high quality galvos or Phenix on Ebay (yes, that's how its spelled) for cheapo / decent scanners. e.g. https://www.ebay.com/itm/DT-30-30K-H...kAAOSwKM9ZsX4H

Assorted Parts (wire, DB25 connectors, Power Switches, etc.): https://www.digikey.com/ assuming you are in the U.S.

Have fun and ask lots of questions!

-David

This is phenomenal! Thanks for the wealth of info here! It's more direction than I have felt I had in two weeks on internet research. All you folks rock here.

I have most of the tools you mention already so this fits in to what I have been doing already and am comfortable with. I have been fawning over those who have made them that I can find on google/youtube and trying to study the inside of them from afar. I think I have gotten the hang of many of the aspects and your descriptions have helped that too. Though I am sure I will be back with questions once the rubber hits the road!

If you happen to know of some great builds that are inspirations to study how they were made, that would be super helpful. I'm now quite excited that I'll be able to put together quick a cool piece of equipment in the end.

Here is a link to my last build. I use all of the same places as David and also highly recommend them.

http://photonlexicon.com/forums/show...ng-a-New-Build!

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Originally Posted by ryanlightsitup

This is phenomenal! Thanks for the wealth of info here! It's more direction than I have felt I had in two weeks on internet research. All you folks rock here.

I have most of the tools you mention already so this fits in to what I have been doing already and am comfortable with. I have been fawning over those who have made them that I can find on google/youtube and trying to study the inside of them from afar. I think I have gotten the hang of many of the aspects and your descriptions have helped that too. Though I am sure I will be back with questions once the rubber hits the road!

If you happen to know of some great builds that are inspirations to study how they were made, that would be super helpful. I'm now quite excited that I'll be able to put together quick a cool piece of equipment in the end.

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Cool! I like your build! Very easy to see everything in your photos too. Thanks!

What David neglected to mention in his arsenal are tiny tweezers and a high powered microscope, since he squeezes all of these goodies into a projector the size of a cigarette pack. :)
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Also "TTL" and "analog" are functions of the driver, not the laser itself. Forgot to mention that. The increase in cost for analog over TTL is really minimal though.
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If you are looking for built modules with drivers to simplify some of the process, since you mentioned buying the lasers pre built and just adding galvos, Goldenstar laser has a wide variety. http://goldenstarlaser.com/index.php...tegory&path=92

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Originally Posted by Bradfo69

Also "TTL" and "analog" are functions of the driver, not the laser itself.

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Ah okay. That is in line with the labelling of what I have been seeing around. And makes sense!

I'll have to do some research, and while I really love the idea of building with the individual diodes, perhaps my first attempt would benefit from a few premade components. It is only my first after all! There may be many more.

You know I do wonder if Pwm over TTL would work. I can't see why not. Would be a lot bettter control on the low end too.

Welcome Ryan!!!

Any chance you like quad-copters or SCUBA diving?

;)

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Originally Posted by kecked

You know I do wonder if Pwm over TTL would work. I can't see why not. Would be a lot bettter control on the low end too.

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You know, it couldn't hurt to do a little experiment once I get the stuff I've ordered! I'll let you know how it goes.

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Originally Posted by HankLloydRight

Welcome Ryan!!!

Any chance you like quad-copters or SCUBA diving?

;)

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Thanks for the warm welcome! I am into a great many things, though both of those have escaped my attention so far, though, I am getting dangerously close to looking into quad-copters as I have always wanted to get some awesome photos from above. Everyone here seems pretty fun and knowledgeable too. I have a feeling I'm going to learn a ton here!

Quote:

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Originally Posted by ryanlightsitup

Thanks for the warm welcome! I am into a great many things, though both of those have escaped my attention so far, though, I am getting dangerously close to looking into quad-copters as I have always wanted to get some awesome photos from above. Everyone here seems pretty fun and knowledgeable too. I have a feeling I'm going to learn a ton here!

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Oh yes, you'll learn a lot! Also, keep the second week of August open. ;)

I'm surprised that nobody has yet mentioned the slippery slope of eventually spending all your free cash on lasers.

Ask me how I know.

Or better yet, ask Bradfo69

;)

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Originally Posted by kecked

You know I do wonder if Pwm over TTL would work. I can't see why not. Would be a lot bettter control on the low end too.

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If you are talking about getting apparent levels that are below the diode's threshold, yeah, I agree. My concern would be having the driver respond to each PWM peak with a slight spike to the diode (as we've seen with many drivers over scopes) that would result in stress/damage to the diode over time. Also if the PWM signal frequency was on the low end, wouldn't this result in crappy video like PWM'd LEDs?

I seem to recall that BBE's drivers can handle PWM input and apparently this is not uncommon output from some DACs, although I don't know which ones.

-David

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Originally Posted by dkumpula

My concern would be having the driver respond to each PWM peak with a slight spike to the diode (as we've seen with many drivers over scopes) that would result in stress/damage to the diode over time. Also if the PWM signal frequency was on the low end, wouldn't this result in crappy video like PWM'd LEDs?-David

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This is where my non-familiarity with laser diode will come into play, but when working with constant-current high-power LEDs, you can use something like this driver (https://www.sparkfun.com/products/13705) that uses a chip (AL8805WS) that is designed to give a constant current based on the resistor value, but also has a PWM pin allowing you to do the full range of PWM.

You're right though, if it's anywhere near how an LED works, the very low end will be kinda crummy. I am not familiar with the stresses that they can endure though. They have the schematic available on how to use that chip, and it's available on digikey. I'm already getting a bunch of these components for some 3w LEDs, so might as well try it out too.

Unrelated question that maybe someone can answer that I have been having a hard time trying to find the answer to. When looking at galvos, I often see their ratings subject to their degree spread (like 20kpps at 20*). So, I am trying to calculate the size of a projected image based on this but I cannot figure out if 20* is from one side to the origin in the center, or the full sweep. To put it another way, if I am running at 20*, is the arc at the largest I can make it (left to right) 20* or 40*?

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Originally Posted by ryanlightsitup

Unrelated question that maybe someone can answer that I have been having a hard time trying to find the answer to. When looking at galvos, I often see their ratings subject to their degree spread (like 20kpps at 20*). So, I am trying to calculate the size of a projected image based on this but I cannot figure out if 20* is from one side to the origin in the center, or the full sweep. To put it another way, if I am running at 20*, is the arc at the largest I can make it (left to right) 20* or 40*?

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The stats are usually expressed as optical scan angle which is twice the mechanical scan angle. Bill Benner has an excellent book on the topic, Laser Scanners Technologies and Applications. You can get it on Kindle using the link provided for a single dollar!

Be wary though that the stats from Chinese suppliers are frequently overstated or simply copied from whatever galvo they were attempting to copy at the time. There are several reviews and discussions of a variety of scanners on PL if you do some searching.

Have fun!

-David

Worth noting, I have nothing bad to say about phenix. Both times I've ordered from them they were extremely helpful and the shipment arrived in a few days. The scanners I've used are of good quality and I have no complaints thus far. And they're perhaps 1/5th the price of what it would be to order from pangolin.

Thanks for the advice. I have found their website, but they don't have direct links to their products and I'm having a hard time matching them up to sellers on ebay. What's the best way to get one of their products?