Smoke Machine – Build Your Own

Smoke machines, pretty common effect used in most haunted houses. I’ve always had problems with them however.

Any time I’m in the smoke the generate I cough a lot, and I cannot stand the smell of the smoke they generate, all those chemicals.

So I set myself the challenge two years ago to build my own smoke machine, but I wanted it to work on just water. I didn’t want to have to keep buying the special fluids to have it work.

After a bit of research online I came across a small device call an ultrasonic mist maker. These are used in greenhouses to make, as the name suggests, a small mist cloud.

I started playing around with a single one in a mug and it worked pretty well. Gave a nice layer of fog in the mug.

So I started to scale it up, I bought a load more of the mist makers (up to about 10). Got myself a PC fan, some extract pipe and a plastic box.

With a bit of cutting I set the fan into the lid on one side and the extract pipe the other. Then once the box was filled with water and the misters plugged in, boom I had a DIY fog machine.

I learnt a few things from this first prototype after using it in my first haunted house display.

  1. Make sure you have the power supply well away from the fog machine! Mine was too close and the moisture fried it.
  2. Having a fan in the lid blowing downwards towards the water wasn’t the best idea.

I found the fan ended up blowing most of the mist back into the water pool, meaning I didn’t get the most output that I could have.

After frying my first prototype I went back to the drawing board.

Unfortunately I didn’t take any pictures of this first design.

I came up with a new design that allowed for full smoke output as well as improvements like not destroying the power supply unit.

My new design which I am still using, has 2 plastic boxes stacked onto of each other. The box on top is being used as a water storage tank. I can leave my smoke machine running all night without worrying about it running dry.

A bit of pipe work and using a float valve from a toilet (a new one not used!) Makes up the filling mechanism for the bottom box. (See top right image above)

The bottom box is where the mist makers live. With holes cut either end. The holes are set just above where the mist makers sit so that the fan when attached at one end will blow across the top and into the ducting pipe on the other side. No more lost output! (See top left image above)

For the wiring, I’ve learnt my lesson. The mist makers go into a sealed box to be joined into a single cable. This then has a long run before hitting the power supply unit so I can now keep the power supply well away from the fog. (See bottom right image above)

When I started testing I played around with the voltages sent to the fan (1.5v up to 12v). I found that the lower voltage/fan speed made a thicker fog but had less coverage. This fog had a tendency to stay low as well.

When I upped the voltage/speed the fog filled my kitchen quickly, but was much thinner, more like what you see on farmers fields on a cold morning. It raised quite high from the ground.

All in I enjoyed making the smoke machine, don’t get me wrong it was more expensive to build my own than buy one, but I wanted the challenge.

I also prefer the fact that I don’t have to buy specialist fluids for it and it does not have the hideous smell that comes from normal smoke machines.

My only last comment is be careful where you use one of these, I found that it tends to make floors and surfaces damp where the mist is condensing, mostly because the mist isn’t heated.

For those of you who want a little more on how the mist makers work;

So most people know about fluids and surface tension, a quick basic if you don’t, the surface of a fluid has a tension force between the molecules holding them together. If you fill a glass right up to the rim and look closely you will see the water actually bulges above the rim but doesn’t flow over, because of this tension.

Well ultrasonic mist makers have a plate the vibrates at a high frequency that gives each water molecule enough energy to break free from the tension. Once free it travels as a small droplet in the air and that’s what your mist is.

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