Witch and Cauldron Silhouettes with Coals

Introduction

We have a set of plywood bear silhouettes set up in our backyard for most of the year, visible from our house and from the street through the woods. This year, I decided to make a Halloween scene to replace them when they first go into hibernation for the fall and winter. The bears would be replaced with a witch and her cauldron, and there would be artificial lit coals under the cauldron.

The Silhouettes

To make the silhouettes, I first needed a pattern. I borrowed a nice outline for the witch

Baack silhouettes of a witch and a cauldron, drawn to scale with vertical and horizontal scaling lines.

Scale drawings of the witch and cauldron

that I found online, modifying it so that it would be easily recognizable, interesting, but within my personal jigsaw skills ability. The cauldron I just drew from scratch. I made scale drawings, with vertical and horizontal scaling lines marking what would be every six inches in the final build.

The purpose of the scaling lines was to make it much, much easier to freehand layout the full-size pattern on the plywood. I went from where each line in the outline crossed a scaling line to the next scaling line, hand-drawing in each segment. Once the pattern was drawn on the plywood at scale, I cut both the witch and the cauldron out using a jigsaw.

I primed the silhouettes with flat black spray primer / paint and then painted them with flat black barn paint.

Two images, one of the witch outline and one of the cauldron outline. Each is sketched onto a piece of plywood, along with scaling lines.

The outlines sketched onto the plywood, using the scaling lines.

Unpainted plywood silhouette of a witch, set on two sawhorses.

The cutout witch, prior to priming and painting.

The Coals

There are many tutorials online for making realistic looking coals using spray foam crack filler, spray paint, and orange string lights. Some, like what I built, are quite simple, while others are more involved, adding real sticks and ashes to make it appear more realistic. Since mine was intended to be viewed from a distance, I decided that there was no need for the added complexity.

A flattened oval black plywood base. On tope is roughly sprayed on crack filling foam, partly covering orange LED lights.

The fake coals, with the first of two layers of crack filling foam applied.

I cut a shape out of plywood with rounded short sides and straight longer sides, with a rectangular slot cut in the middle to fit the cauldron and support stakes. After painting it black, just as with the silhouettes, I cut a piece of scrap 2×4 to set over the slot, so that the crack filling foam wouldn’t expand into that area and block where the cauldron would go. I wrapped the 2×4 piece in a plastic garbage bag so that the foam wouldn’t stick to it. Next, I laid out the string of lights. I used a 100-light string of orange LED bulbs. You could probably get by with a 50-light string, but I liked having more lights. Some people use plastic cups or cut pieces of soda bottles to go around each light, but others don’t bother, and I didn’t. I figure there’s little heat coming from each bulb, so hopefully the string will last for years. I have heard of one person who used incandescent mini bulbs and a fire somehow started, so I’d stick to LED bulbs.

Once the lights are laid out around the platform, you just spray on the crack filler, keeping in mind that it will expand some. You want the lights partially or entirely covered to look more like hot coals. You can go a little light the first time, and then once the foam dries, add more where it’s needed.

Black plywood cauldron silhouette and fake hot coals (painted crack filler foam with embedded lights).

The finished cauldron and hot coals.

Next, I removed the 2×4 piece and used the same spray primer / paint to lightly go over the foam. The nice thing is you WANT the paint to be uneven, with some heavier, dark spots. Finally, I added some red spray paint highlights.

The last thing I needed was a spotlight to light up the silhouette at night. The coals show up clearly from the sidewalk and street, but the black silhouette is too dark without a light on it. I found a multi-color adjustable spotlight online that works great for this.

Final Results

The pictures here show the final result, from both sides in the daytime, and from the street at night, with the spotlight illuminating it.

Finished witch and cauldron silhouettes, with the cauldron on the fake hot coals. It is installed in a yard with trees in the background and leaves on the ground.

The installed project, viewed in the daytime from the back of our house.

The witch, cauldron, and "lit" coals (LED lights lit), seen at night. The silhouettes are lit by a spotlight.

The final project at night, as viewed from the street. The spotlight illuminates the silhouettes.

 

Crowd-Sourced List of Python Resources Related to Halloween

An AI-generated image. bats fly overhead, with a full moon visible. On the left is a laptop showing some computer code. In the middle is a pumpkin with the Python logo carved in it. There is also a black cat with green glowing eyes. If you look at this blog, you’ll quickly see that many of my projects relate to Halloween. I don’t know if this is a good, bad, or dumb idea, but as I was thinking about my use of Python for controlling Halloween props, I had the thought that it might be nice to have and share a crowdsourced list of python-related resources relating to Halloween, such as useful libraries (e.g., pyAudio, various libraries for using the GPIO pins on a Raspberry Pi), complete software packages (e.g., my own ChatterPi), or even Halloween-themed games written with Python. So, with some help from ChatGPT, I’ve put together a Google sheet, Python Resources for Halloween,  with some pre-populated content that anyone can view, along with a Google Form, Submit Python Resource for Halloween, where anyone can submit additional resources for inclusion.

The submissions are moderated, so they won’t show up immediately in the resource sheet. If you have anything to propose adding, please do so using the Google Form. If you have any other feedback, I welcome it as a comment on this post.

Pi-based multi-prop trigger for animatronics, Part 1

Next Halloween, my setup will include three coordinated skeletons performing together (probably doing “King Tut“). I want to use a single PIR motion detector to trigger three different props at different offsets from the original trigger. And some of the props can only speak or move for short amounts of time, so for a longer performance, they need to be repeatedly triggered. To do this, I have a PIR providing input to a Raspberry Pi Zero W. A python program running on the Pi then sends brief output trigger voltages individually to each of the props, according to the preset schedule for the routine. This same approach could easily be modified to trigger 2, 4, 5, or more coordinated props from a single start trigger. The hardware setup is very simple, and is shown in the figure.

Wiring diagram for the multi-prop trigger. The left is a Raspberry Pi Zero W with the pins enlarged, and the right is a breadboard. The breadboard has a barrel jack for power (that also is wired to the Pi). There are four 3 pin female headers on the breadboard. One is for the PIR sensor, and has all three connections wired. The other three are to send signals to three props. These have the ground and signal wires connected.
Wiring diagram

Power is provided via the barrel jack on the prototype board. This is also what powers the Pi. Their are four 3-pin female headers on the board. The one on the left is for the PIR sensor input. It has the power and ground connections, and the signal wire is an input that goes to GPIO pin 15 on the Pi. The other three headers are to go out to the three props. The grounds are connected so that the prop controls and this trigger share a common ground. The signal connections are outputs from GPIO pins 23, 24, and 25. There is no need for power for these connections. 

In order to test the hardware, I rigged up one LED to each of the three signal outputs, put a resistor in to avoid burning out any of the LEDs, and linked the grounds. The test setup is shown below below:

Picture showing a Raspberry Pi Zero W on the right, with soldered connections to a soldered breadboard with a 3 pin header that a PIR sensor is plugged into, and three other 3 pin headers that connect to a solderless breadboard with three LEDs connected.

Test setup to make sure the hardware works and that I got the soldering correct.

I used the GPIO Zero library to write a simple test script for this test setup:

from gpiozero import LED
from gpiozero import MotionSensor

myLED1 = LED(23)
myLED2 = LED(24)
myLED3 = LED(25)
pir = MotionSensor(15)

while True:
    if pir.wait_for_motion():
        print("motion detected")
        myLED3.off()
        myLED1.blink(1)
        myLED2.blink(2)
        pir.wait_for_no_motion()
        print("no motion")
        myLED1.off()
        myLED2.off()
        myLED3.blink(3)

This has the pi wait until the PIR detects motion. Then it begins blinking the first 2 LEDs at different rates. When motion stops, those two LEDs are turned off and the third LED begins to blink. This cycle then repeats until the user hits CTRL-C to stop the test script.

Black project box without the top. It has a large round opening where the barrel jack for power resids, and a large rectangular opening where the micro SC card can be accessed. Inside are the Pi Zero W and the solderable breadboard.

Completed electronics in project box

Completed project box with electronics inside. The cover is on to top. You can see the solderable breadboard with headers through the top cutout.

Completed project box with electronics inside and lid on the top

The circuit is mounted in a custom 3d printed project box with slots for the power, sensor, and output wires, as well as a slot for accessing the Pi’s micro SD card. I designed the box using TinkerCad. I also 3d printed the standoffs, and just used hot glue to glue the Pi and the breadboard in place. I put in large holes so that it would be easy to plug and unplug the connectors and also get my fingers in to insert or remove the micro SD card. The top has a large cutout to make it easy to access the 3-pin headers. The finished hardware is shown in the figures on the right.