Yeah, I've got like 10 build threads going here, so what better time to start a new build thread?

I am making a Soul Cage for Halloween. Right now I'm in the waiting for parts phase. In the meantime, here's the Hackaday article that caught my interest.

https://hackaday.com/2025/09/25/trapped-soul-in-time-for-halloween/

🧵 1/N

#SoulCage #BuildThread #ESP32

Trapped Soul In Time For Halloween

While it is sort of disturbing, it is one of the best uses for a round LCD we’ve seen lately. What is it? Just [vishalsoniindia]’s SoulCage — a pendant that appears to have a poor…

Hackaday

While I wait, I thought I'd try obscuring it by flickering the LCD's backlight on and off. Here's a flickering backlight on a test pattern on the Reaction Diffusion Toy (different screen, same MCU).

🧵 2/N

#SoulCage #BuildThread #ESP32

Here's the brightness function. Sum of sine waves, un-gamma-corrected and rectified. The pattern repeats every 50 seconds.

No idea how it will look with the Soul Cage animations.

🧵 3/N

#SoulCage #BuildThread #ESP32

While waiting for parts, I printed the Soul Cage's housing (left). The Waveshare board comes with a machined metal housing. This printed part replaces the housing's back cover and deepens it to make room for a battery and a power switch.

I wanted something with more character, so I designed the one on the right. I found a nice 3D printed chain on Printables, and I added spike/loops to pass the chain through. The idea is that the soul is chained in.

🧵 4/N

#SoulCage #3DPrinting

The gray in the previous photo is just a working color. It photographs well, but I want something spookier. I picked up this fidget spinner at 3DPrintopia, and that's the filament I want. Do you know what it is? I sent email to AsylumLife, but no answer yet.

I will get some PolyMaker Shadow Red Dual Matte PLA if I don't find out what it is.
https://us.polymaker.com/products/panchroma-dual-matte?variant=43613087825977

🧵 5/N

#SoulCage #3DPrinting #Filament

AsylumLife responded. It was a limited edition filament, now gone. So I'll try plan B.

#SoulCage #Filament

Gotta decorate the case back. This is an attempt. Man, Fusion 360 fights you every inch of the way when you want to add lettering or artwork to a surface.

🧵 6/N

#SoulCage #3DPrinting

I designed a magnetic clasp for the Soul Cage's chain. There's already a magnetic clasp on Printables, but this one also has a mechanical engagement. It should be more secure.

I used my now-standard crush rib design to hold the magnets. I will Superglue them in too.

🧵 6/N

#SoulCage #3DPrinting

I'm adding static bursts to the Soul Cage video in addition to the flickering backlight. Here are the effects applied to the test pattern thing.

Why? The Soul Cage's video loop is only 8 seconds long. It's 8 very good seconds, but it does get repetitive. So I'm looking for ways to distract the viewer from noticing.

I've also tweaked the screen flickering algorithm to make it less repetitive.

Edit, 2 days later: 8 seconds, not 2.

🧵 7/N

#SoulCage #ESP32

This build thread is brought to you by Staples®.

I've used reams of paper as monitor stands for 40 years. They're cheap, they're solid, and they used to be ubiquitous in office environments.

🧵 8/N

#SoulCage #Staples

@kbob Reminds me of that time when LinusTechTips came to our lab and hyped our ultra-high precision equipment that’s used to measure Staples supported LCD panels: https://m.youtube.com/watch?v=Um0PFoB-Ls4&t=380s
Look what we found in NVIDIA's Top Secret Gaming Monitor Lab

YouTube