Now that my son is 13 months old I finally had at least a moment or two to work on a Halloween display so naturally I wanted to get some automation activities integrated with my platform of choice, the Raspberry Pi.

Note: My code is available at the bottom of the project.

My goal for this project was to use every trick I could with a minimal budget to scare as many neighborhood kids as I could. Mission Accomplished.

Here was the rough order of operations.

Motion sensor runs in a loop looking for motion. When motion is detected start the smoke machine smoking immediately and run for all additional events in the list. Wait for a moment or two then cut all of the exterior property lighting. Wait for another moment then play one of the spooky sounds from the hidden speakers in the bushes very loudly. Revive the property lighting. Wait 15 seconds then repeat.

Controlling the Smoke Machine

The first order of business was to reverse engineer how the smoke machine remote actually works. Two years ago I had purchased the biggest non-commercial smoke machine I could find as part of my annual Halloween budget. That first year I just used the included remote but even then I knew I would eventually have to figure out how to automate the smoking functionality. I know they also sell remotes that don’t have the simple on/off button like mine has; instead you can pay $16.99 for a remote with an interval smoking function from a store like Spirit Halloween– but again, I didn’t want an interval– smoke juice is expensive I want to use it only when a person is actually nearby to enjoy it. So this led me down the path of figuring out how to control it.

Using a standard multimeter set to measure resistance I determined what each of the 3 pins in the remote did and determined that in order to produce smoke I needed simply to bridge two of them. This is the enterance-point for my 4-way relay I had purchased a year ago for just such a task.

Hooking up the relay to bridge the necessary pins I was able to produce smoke — SUCCESS! Now to set this up a little more permanently, as it turns out the remote is actually switching 120v wall power so extra care is needed when wiring this up to do it right. I obtained some extra lumber I had from another project and started building a control board that everything would be permanently affixed to.

At this point, I’ve used a combination of drilling and ziptieing to secure the raspberry pi (with case), breadboard, and relay bank to the control board which was a sheet of 1/4 inch MDF.

Adding Motion Sensing

The next phase was to setup the smoke machine to fire when motion was detected. To accomplish this I used a cheap PIR sensor that I had purchased off of E-bay last year for about $3.00 via the direct from China route.

It took a bit of adjusting on the PIR sensor to get it setup correctly for my application. In this case there are two adjustments, one is sensitivity, and the other is time-delay (how long the signal wire stays high when motion is detected). For this project I essentially set the PIR sensor to maximum sensitivity and the shortest time delay for a hair-trigger. I wanted to maximize the granularity of the sensor and push the false positive detection into software where I could control it with variables in a program instead of by turning physical knobs.

Once configured I did a bit of trial and error by moving back and forth in front of the sensor in my garage. My neighbors would probably have thought me crazy moving back and forth in my garage for 15 minutes but they know better by now. I found that the effective range of the sensor was about 15 feet.

Now that I had the sensor working with some test code (included PIR_test2.py) it was time to setup some spooky noises to be triggered with the motion sensing.

Setting up the Audio

I wanted to use the included headphone jack on the Pi to play audio into a little class T amplifier (I swear this used to cost just under $20 when I bought it, it has AMAZING PERFORMANCE for the price) and an old pair of extra speakers that had been collecting dust around my workshop.

As it turns out there was an issue with some of the updates I had performed most recently on my Pi that left my audio broken, after a bit of soul-searching on google for the error message I saw when trying to use Aplay to play a sample audio file I decided to do some updates and see if that would solve the issue.

sudo apt-get update -y && sudo apt-get upgrade -y

Sure-enough my audio was now working with Aplay after the dust cleared from the updates and a reboot was performed.

At this point I began searching the net and collecting spooky noises from various sound effect websites. I collected all ten of the wav files which made the final cut and renamed them from 1-10 (My code actually randomly generates an integer from 1-10 and plays the corresponding file 1.wav – 10.wav for simplicity).

Adding The Exterior Lighting Control

Since the majority of my exterior property lighting is already wired for automation with WEMOs I wanted to include this in my Halloween setup. I bought 3 red LED bulbs and went to town replacing the exterior lights with an eerie red glow. They actually created a lovely scary effect. The bulbs were certainly not cheap though.

Regarding the code for the WEMOs, I already had this code built from various WEMO projects but I wanted to do something very simple for this project, just an on/off, no database tracking, no fancy behaviors, no logging etc. so I re-wrote some of the code to run a little faster and added a little pair of bash scripts (allon.sh and alloff.sh) to bring up multiple switches in rapid succession, the effect is truly instant when kicked off in this manner so I was very happy.

Carving the Monster Pumpkin

I’ll have to add a picture of the beast when it was all carved but I picked up a gigantic pumpkin from the Raleigh State Farmer’s Market for $50. I’ve always wanted a pumpkin this big. I figured with this no one would be able to doubt my Halloween spirit. This pumpkin was so large that it took two grown men to move it on a towel. I honestly could not lift it myself which was very emasculating but also thrilling that it was so incredibly huge.

I know I have a carved picture of it somewhere but I can’t seem to find it at the moment so I’ll post that bit later. These super huge pumpkins are actually a different species and produce really nasty seeds that you can’t cook up which is an interesting fact I learned when I opened this bad-boy up.

When the scary face was all carved I then carved a 3inch diameter hole in the back for the dryer hose…. dryer hose you ask? Of course you need dryer hose when you’re…

Building the Fog Chiller

One of my favorite pieces of Halloween tech is a good fog chiller. When you cool the fog down to a temperature that is lower than the outside air it will actually sink down to the ground and drift along making an extra scary effect. This was a trick I masterminded when I was organizing the annual public Haunted House in my fraternity days. The effect is great and luckily I had an old 50 gallon plastic drum that I had purchased off of Craigslist several years ago that was a perfect fit for the project.

Essentially you cut a hole in your container, coil the dryer-hose around within the container then run the hose to your destination which in my case was the back of the gigantic pumpkin. I also added a string of green LED lights in the pumpkin as well to give the fog a cool effect.

Lastly you fill the container with a combination of ice and water. I actually began saving up ice from my refrigerator and storing it in my chest freezer several weeks in advance in order to be able to fill up the drum and not spend any direct dollars from the Halloween budget on frivolous things like store-bought ice.

Putting All the Pieces Together With Code

Now that all the individual pieces were functional all that was left to do was to write the code to unify the individual pieces and create the coordinated show.

This code can be found in the halloween.py file.

Results

The effect was awesome! Many neighborhood kids and parents were scared some wouldn’t even set foot on the property which is a personal win because that means more candy for me and as an adult lets be honest, there are few joys in life like making kids you’ve never met cry. I will probably grow this by adding motion activated lawn effects next year but this year was a total success!

Get the Code

I’ve posted my code from the endeavor to my github page in a new Halloween 2015 repo: https://github.com/ericpulvino/halloween2015