Controlling a Fog Machine with SmartThings

With Halloween upon us I wanted to share my recent success story integrating a Fog Machine with ST. I’ve always wanted to create a ‘smart’ fog machine that I could integrate with the rest of my Halloween decor, with the ultimate goal triggering the machine on motion. I’ve seen projects on instructables using a localized PIR to trigger the machine but felt they were ‘lacking’ because it effectively required the guest to be in the vicinity of the machine to trigger.

I currently use ST for the automation of my exterior lighthing (among other things) and automate that lighting using several Monoprice ZWAVE PIR placed under the eve’s of my home in strategic locations. The goal; leverage my existing motion detectors to trigger a inexpensive fog machine, while still retaining the original control mechanism in the fog machine.

First up purchase the fog machine. I ended up getting this unit for $35 plus a gallonew of fog juice for $15.

Next up controlling the machine with ST. A Zwave relay wired into the trigger circuit seemed the way to go. Fog machines are generally controlled with wired ‘remote’ that will only operate once the machine is hot enough. A red light on the remote will illuminate when ready. The wired remote did not have enough space to add a relay directly to it, so I cracked the case on the fog machine where I found plenty of room.

Once inside I realized that the remote was opening the circuit between the juice pump and neutral after the load. Okay simple enough, wire my relay into the device hot and neutral, and add the switched circuit in parallel with the existing remote. This would leave the originally remote intact, provide some kind of manual control, as well as retaining the status feedback on the remote. I addition the device was registering on the Zwave network as long as the machine was plugged in, but the trigger would only work when the machine was hot enough.

My first attempts at this failed as while I could get the machine to trigger from ST, the trigger would operate at any time, even when the device was cold. I realized that I need a dry contact relay to make this work. Most of the Zwave micro relays are wet contact meaning that voltage is present on the switched circuit even when in the off position. I just happened to have a linear zwave relay let over from another project. I would actually recommend one of the other true dry contact relays as the linear relay was a bit bulky for the fog machine.

After I wired in the new relay I was able to turn the machine on/off remotely. Now integrate the machine with the PIR’S. Using CoRE I was able to create a piston that turned on the fog machine for 30 seconds after the monitored PIR’s changed its state to active.

That’s about it.


Would you be willing to supply some pics of what you did? I’ve been contemplating doing this exact project.



Unfortunately I didn’t take an pictures of the wiring inside the fog machine. It’s pretty straight forward though and I wouldnt recommend the relay I used unless you allready had one lying around. I actually modified the linear to have the wires exit on the side, normally they exit on back. That relay is rated to 20a, the whole fog machine is 400w and most of that is the heater, so 5a relay would be more then enough. Just remember it HAS to be dry contact.

I used wire nuts instead of resoldering everything. You may need to add ‘extensions’ to some of the wires as there may not be enough play in wire for stripping and nutting.

Your relay will have a load and a line side.

The line side is super simple;

  • Connect the relays hot on the line side to the black wire where power enters the unit. My machine had a fuse just after the point power entered the unit, so I tapped in after that for a little extra protection for the relay. Make sure to reconnect any wires you cut to make the tap.
  • Connect the relays neutral on the line side to the white wire where the power enters the unit. FYI -You will also connect one of the load wires here, see below, just nut them all together.

The load side. This is no different then a wall switch, so there is no concept of hot and neutral.

  • For one of the load wires connect it to the neutral along with the line side neutral.
  • For the second load wire you will need to do a bit of investigating. You will need to connect the wire from the pump to the switched load on the wired remote. You will likely have two wires connecting from near the pump to the remote. One will connect to the led ready light the other will connect to the switch on remote. The latter is the wire you want, mine was yellow. Both circuits use a common return ‘white’ wire that connects to the neutral, we allready accounted for this wire above so skip it. When I looked at my unit I passed pretty sure the yellow wire was the one I wanted but wanted to be 100% sure. So I cracked open the remote casing and traced back the wires in the remote back to the unit using a continuity tester. Ensure the switch is in the open position, look for the soldering points where the switch is soldered onto the pcb, use the soldering point that is NOT electrically connected to the led, put a lead on that connection and then test the wires in the smoke machine leading to the remote. The wired you want will show continuity, the other should show as open.

Hopefully that helps,

Quick update. Fog machine worked flawlesly tonight. Had to take my daughter trick-or-treating, left the candy bowl on the front step, and started knocking on neighbors doors. While standing in the street I watched several kids approach the house, as soon as the driveway PIR picked up the motion, fog machine triggered for a 30 second bast, fogging out the entry to home by the time the kiddos reached the house. Kids thought it was great (well all but one) and I avoided having the fire department called on me.

Next up I’m going to try and make a chiller so the fog hugs the ground and try to find a large cauldron on clearance to put the candy bowl in. Shoot the chilled fog into the bottom of the cauldron for the ultimate Halloween prop.

I’m a visual guy, but this sounds like a great thing to do! If anyone builds one, please provide pictures and parts numbers for switches/relays.


You say you would recommend a different wet contact switch. Can you provide a link to recommendation?

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I’d probably use the Remotec ZFM-80 ( if I didn’t have a spare dry contact lying around. It’s rated to 15amp’s and very compact. You could even drill additional holes on the back of the fog machine for the push button switch and status light. Might even be able to wire fog machines remote switch thru remote leads on ZFM-80.

Word of warning; I learned the hard way you HAVE to have a manual switch on remote switch leads of the ZFM-80 to get the damn thing into inclusion mode. This was not called out in any of the switches documentation and i almost returnec my device as defective. Once it’s on the Z-Wave network you can remove the switch.