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Fog machines are lots of fun, especially at Halloween.  But the ones you can get at most party stores either come with a basic remote that means you have to push a button to get a blast of fog, or they have a remote with a built-in timer, which blasts fog all night every few moments...even if no one is there.  And then you run out of fog juice.

I'll show you how to make a replacement for the standard remote that you can control with any microcontroller (Basic Stamp, Arduino, Picaxe, EFX-Tek Prop-1, etc.)  I'm going to assume you know how to program and connect your microcontroller.  This Instructable is about making the control box for the fog machine.

You could just use a motion sensor and a microcontroller to blast kids with fog as they came up to get candy, but this also lets you incorporate the fog machine into a more elaborate scene...trigger a sound effect, a light, or a moving prop, and include a blast of fog as well.

Step 1: Parts and Tools

Parts: 
1x 5V Relay Module – www.dx.com SKU: 157153
1x IEC extension cable – this will connect to your fog machine.
1x Project box - comes with screws to hold it closed in a small plastic bag.  Jameco Part no. 675462
1x Stereo plug  Jameco Part no. 231176
1x Stereo jack  Jameco Part no. 2095437
4x Screws 4-40, 1/2”
4x Nuts 4-40
1x 1” piece of plastic tubing, ¼” outside diameter, for stand-offs
1x Servo extension cable – connects the relay to the stereo jack
1x 3-wire cable – connects the stereo plug to the controller, 12” or more if needed
1x zip tie
Heat shrink tubing

The parts list is attached as a handy Excel file, with part numbers and websites.  You can substitute similar parts for many of these.


Tools Required:
• Soldering iron
• "Helping Hands". You can make one yourself, check these out:
https://www.instructables.com/id/DIY-Helping-Hands-Cheapest-and-Quickest/
• Wire clippers
• Wire strippers
• Small flat blade screwdriver
• Small Phillips screwdriver
• Small needle-nosed pliers
• Tweezers
• Hot Glue gun and sticks
• Exacto knife and something to cut on (small board, etc)
• Multimeter
• The remote from your fog machine
• Power drill with assorted bits
• Hot air gun or hair dryer (for heat shrink tubing)
<p>For mounting the mini TRS jack, instead of counter-sinking the ring, I found there was plenty of plastic to tap the sidewall with M6x0.5 threads and screw the jack in, which comes just about flush with the exterior. Maybe it wouldn't hold up to abuse, but seems pretty solid for occasional use. I hot-glued the jack to the inside wall just for a little extra sticking power.</p>
<p>Nice tip. Hot glue to the rescue again!</p>
<p>Thanks for the inspiration. I 3D-printed a project enclosure that I designed to fit my parts, which cut down on the work to create standoffs and countersinking for the jack. In hindsight, I should have designed a strain-relief for the cable.</p><p>I had a two-relay module sitting around, so one relay is unused. In the future, I'd probably consider using RJ-45 (network cable) jacks for the low-voltage signals. That would make it possible to carry more signals around and perhaps make use of the second relay.</p>
Wow, very nice. I don't have a 3D printer yet, so I haven't tried any of these types of projects.
<p>Nice article. I have two recommendations: (1) Consider using plastic screws and nuts to hold the relay board in the box. On some of the relay boards, the mounting holes are very close to relay terminals. If a metal screw head were to touch a hot lead, the screw could conduct high voltage outside the box. (2) The opto-isolation doesn't isolate the high voltage from your low-voltage circuitry; it's the relay that does that. The opto-isolation protects your low-voltage circuitry from the electrical noise made by the relay. Electromechanical devices like motors, solenoids, and relays create back-EMF that can damage sensitive electronics. The opto-isolator protects the microcontroller from the back EMF of the relay.</p><p>Anyway, you've inspired me to build one, so thanks for putting this together!</p>
<p>You're right about the plastic screws. Since I wrote this a couple of years ago, all these little microcontroller modules have just gotten cheaper and cheaper...and as they shrink the size of the circuit board to save a fraction of a penny, you could easily have a screw touch the wrong place and provide path for the voltage out of the box.</p><p>I didn't expect that two years later you would be able to buy these relay modules from ebay, built and with shipping, for less than the cost of the parts! Of course they're not quite as nice as the ones from two years ago, but what are you going to do?</p><p>And thanks for the correction on the isolation. </p>

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