Halloween Hacks: Motion Sensing Fog Machine

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[monkeysinacan] wanted to add a fog machine to his Halloween display, but he says that the cheaper consumer-grade models are pretty unruly beasts. He cites short duty cycles and tricky fog control as his two biggest gripes with these sorts of foggers. He decided make the fogging process a little more manageable, and modified his to only generate fog when someone was walking nearby.

One obvious concern with this sort of setup is the warm-up time required to get the device ready to produce fog. If it were to only turn on when someone walked by, [monkeysinacan] would miss his mark each and every time. To ensure that his machine was accurate, he rigged it so that the heat exchanger stayed powered on, triggering the fog juice pump as needed.

To do this, he used an ultrasonic sensor similar to, but cheaper than a Parallax Ping unit. Paired with an Arduino, the sensor triggers the fog machine’s pump for 20 seconds whenever anyone gets within 6 feet of it.

While he hasn’t posted video of the modified fogger at work, it sounds like a solid plan to us.

6 thoughts on “Halloween Hacks: Motion Sensing Fog Machine

    1. THIS^^^^^

      Most fog juice is either a solution of ethylene/propylene glycol or there is another version which is not water based and is essentially mineral oil.

      Neither of these nasty chemicals should be intentionally vaporised to be inhaled by kids trick or treating.

      The bottle of fog juice says so as well.

      This hack may provide an automatic dispensation of fog, but if I run into this machine, it will engender an automatic dispensation of ~crunch~

      1. *sigh*…..

        I’m not trying to be harsh, but there is something that really gets to me about times when people including makers have no idea about, nor provisions for the safe use of, nasty chemicals in their projects.

        This reminds me of the “neat DIY trick” of pouring a little gasoline on an anthill in order to kill the insects, or simply pouring used PCB etchant down the drain, ignorant of it’s poisonous heavy metal content.

        Certain “entertainment” consumer goods like this fog juice and certain kinds of fireworks contain materials that are toxic to those around you. I’m sure that I’m not the only one who has suddenly realized that the reason I was coughing was the puffs of Ick that a nearby machine of the nature was wafting in my general direction.

      2. What? Any commercial fog juice is going to be propylene glycol, and that’s about as non-toxic a substance as you can find. The exhaust from the cars going by does the kiddies more damage.

  1. consumer grade foggers are kind of a joke all around. I think it’d be fascinating to see someone build a proper fog machine for a DIY price. They’re not complex machines, but if you need any kind of output or controllability you’re going to pay for it.

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