Well, a concept is all very well and good, but if the parts are unaffordable or unavailable it isn’t going to be much good. It took me a little while to find some good places to buy from, and here’s what I found out.
I wanted a powerful laser, but it had to be able to run for a few hours at a time. A laser light show isn’t a laser light show if you have to shut it off after the first song – well, I suppose it is, but it’s a bit annoying if you’re trying to make a night of it.
A small green lab laser module fits the bill. Green is far more visible than red while still being affordable, unlike horribly expensive blue lasers. You need a lab module, or at least some form of heatsink – laser pointers, especially at the price point we’re looking at, will build up far too much heat in extended operation. This is the biggest expenditure in the project, and one you should take a bit of time looking for.
After much deliberation, I settled on a 35mW unit from DealExtreme. If you like my idea and instructions, please buy your laser through that link – it doesn’t cost you anything extra, makes sure you get the right part, and gives me a tiny bit of commission so I can keep building cool projects. The classic tradeoff of cheap, fast, and good – choose two comes into play here. This DX unit received pretty good reviews, and the price is right at ~$60. Just don’t expect the included free shipping to be lightning fast (they’re based in Hong Kong) and you’ll be alright. It took me a little over 2 weeks to get mine in Canada.
It throws an incredibly bright tiny beam and doesn’t heat up easily, perfect for our show.
Power Supply and Housing
Now that we’ve figured out what laser unit we’re using, we need to get a power supply and place to put everything. I went to Jameco, because it had amazing selection while still being accessible to the individual consumer – all part numbers specified are from them. I bought a regulated 6V 500 mA AC/DC adapter (#283573), which means that it has circuitry that ensures it always supplies 6V, unlike cheaper units. The laser itself draws ~ 380 mA, so I rounded up a bit to be safe. I also got a switch to turn everything on and off (#316111, I recommend getting a DPDT switch), a connector to plug the AC/DC adapter in (#281851, make sure it matches your adapter), and a nice plastic box (#675542) to hold it all.
This is where the magic happens, and what our whole show relies on. Make sure these stay clean and scratch-free. We need:
- a small circular mirror. I’d suggest a ~1cm (roughly 3/8″) mirror. Better mirrors will reflect more light more cleanly, keep in mind. There’s something called a “front surface mirror” that is ideal, but don’t worry too much if you can only get a regular one.
- a diffraction grating. I bought a high quality glass one (specifically the “transmission matrix” model from Dragon Lasers). You can also get sheets of holographic diffraction grating film, I suggest the double axis film from rainbowsymphony.com. If you’re Canadian like me, the easiest option in terms of shipping is the Dragon Lasers grating. It’s a bit odd since they’re in China and rainbowsympony is in the US, but I don’t set the shipping rates. Please post in comments if you find an international source of diffraction grating film sheets at a vaguely reasonable price.
Grab an old pair of big headphones, we’re going to use the speaker and cable from it. The bigger and louder the better – this generally means the speaker will move more, generating bigger patterns. You want the big ones that go completely over your ears, anything smaller will just cause the laser to vibrate a tiny bit and not really make any interesting patterns, unless you’re after a Star Trek meets caffeine overdose effect.
I found a good (albeit gaudy) pair at Radio Shack on sale for $14, which had the added bonus of coming with flashing lights that lit up to the music. Perfect!
You’re also going to need some other basic materials:
- a soldering iron, solder, electrical tape, and wire are a necessity. If you don’t know how to solder, don’t worry – just grab an old broken piece of electronics (the older and simpler the better since the parts will be spaced out more and easier to learn on), check out a soldering guide like this one, and practice removing and resoldering components. There’s no shame in spending a while on this and playing around until you’re confident – after all, if you’re like me, you only ordered one laser!
- a glue gun helps to keep everything organized and in place. Just be careful to not get glue everywhere!
- some balsa wood or popsicle sticks to mount the speaker and align the height of the the laser to match up with the speaker
- a Dremel tool is useful to drill the odd hole or two in your box. An old soldering iron will do in a pinch if you’re using a plastic box like I was, have steady hands, and don’t value your lungs too much (or ventilate appropriate)
- miscellaneous screwdrivers and hand tools always help (especially for taking apart the headphones)
Got all the parts? On to assembly!