Project Showcase: DIY Ray Gun

Exciting parts call for exciting projects. This one turns a dangerous laser into a sci-fi ray gun.

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I had an engraving laser just laying on my desk and a coworker says to me, “You should make it go ‘pew pew’ when it lights up.” I felt some obligation to make that a reality. The world needs this to exist. With parts gathered, it was time to CAD, cut, solder and PEW!

Overall the project went really well, but there were some problems.

The original battery (for which the handle was designed) went bad and I replaced it with a lame-o 9V. It was a two-cell lipo, which produces 7.4 volts. This was on the fringe of what the laser required, so when the battery got low, the laser stopped firing even though there was still sound. Also, during the build, I intended to replace the lame-o 9V with a fresh one, but forgot. Now the battery is dead and difficult to get to.

One disappointment is the reset time of the audio chip. From the time it completes playing one sound file, it takes over a second before it is willing to start playing the next, and it cannot stop midway through playback. For the ray gun, I like to think the laser needs a moment to cool down before the next shot. That makes me feel better. The Little Soundie is still a great sound board. It is well suited for applications that do not require rapid playback from one track to the next.

Perhaps the biggest oops of the project is the mode selector switch. While filming the time lapse of assembly, I broke two wires off. It selected the three modes of fire, which played different sounds and increased power to the laser. Default is “stun” and I called the others “kill” and “vaporize.” They sounded like “pew,” “wah-wah-wah-wah-wah,” and “wee-wee-wee-wee-wee” respectively.

Big wins

The parts fit as expected. I know you’re supposed to account for the kerf of your cutting tool, but I didn’t. I just laser cut the layers from 3 mm plywood. The spray paint covered my laziness and everything fit tightly. It feels solid when held.

I learned a lot about CAD. I’ve had formal training on AutoCAD, but Fusion360 is a whole other animal. It’s a real pleasure to work with, and there are a bunch of tutorial video on the web to help. The best part is it has a free license for hobbyists like me. The platform enabled me to share the CAD source if you’d like to adapt it to your own ray gun. The Arduino sketch is here.

It was a blast to build and I recommend you build one too… except for the dangerous bit of a laser that could cause bodily damage. Pick a safer laser.

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