My yard dragon is holding a little metal orb, which is just perfect for hiding some sensors and electronics. Find a spot on your project where you can hide the PIR sensor at kid-motion level.
I secured it in place with some packing tape.. not a permanent solution, but it'll hold through Halloween.
I got a 10' USB C cable from Amazon and ran it through the back of the orb and out the bottom of the dragon, so the electronics and the fog machine can be powered from the same extension cord.
I sealed up the ends of my NeoPixel strip using hot glue and clear heat shink. Then I threaded the strand down through the mouth and into the belly of the dragon, where I was able to grab the JST connector and thread it in through the back of the orb, where it can plug into my electronics enclosure.
To get the smoke where I wanted it, I bought a Fog Tube Accessory Kit from Home Depot. This came with a long tube that had holes cut all along its length, and a screw-on adapter for the front of the machine.
I cut the tube to the right length and taped up all the holes with gaffer's tape. I want the smoke to come only out of the end.
I dropped the fog tube down the back of the dragon's throat, alongside the NeoPixel strip. I ended up taping the two together to keep them in place. The tube comes out the bottom of the dragon where it attaches to the fog machine.
Extra smoke spilled out through the dragon's eyes and a hole in the top of her head, so I covered the holes from the inside with clear packing tape. Now the smoke just comes out her mouth and nose.
The PIR sensor has a couple adjustment screws on the side, one of which changes sensor sensitivity and the other which adjusts the amount of time between trigger and reset. Play with the settings until your project is all dialed in.
Thicker Smoke
Halloween store fog juice is easy to find at a certain time of year, but we can get much thicker and more dramatic smoke by making our own fog juice.
The ingredients are Glycerine and Propylene Glycol, mixed 50/50 or to your liking. Add a little water if you'd like to thin it out.
If you get a little heavy-handed with the glycerin, it may clog your machine. If this happens, run some vinegar through the machine until the clogs clear out. In fact, it's a good idea to do this whenever you put the fog machine away for storage or after a night of heavy use.
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