Most fluid simulations on LED matrices look great and say nothing. The whole effect is visual, and the moment you look away it goes silent. Maker Tim Alex Jacobs, who goes by Mitxela, wanted the opposite: a fluid sim you can hear from across the room, so he built one on an electromechanical flip-dot panel instead of pixels.
From Wearable Pendant to Room-Filling Panel
Jacobs had already run Matthias Müller’s FLIP (fluid-implicit-particle) simulation on a small LED pendant shaped like mercury sloshing under glass. The flip-dot version scales that same physics engine up to a salvaged transit-sign display, sourced through fellow maker Sam “Look Mum No Computer” Bartle. The donor panels were smaller than he needed and wouldn’t tile cleanly, so Jacobs cut the boards down and built new driver circuitry to flip the dots fast enough for smooth motion.
50 Amps of Clacking Dots
Flip-dots normally draw power only when they change state, which is the whole appeal for low-draw transit signage. Flip a full panel’s worth at once, though, and the current spikes to roughly 50 amps, enough to fry Jacobs’ first driver board. His fix was scattering electrolytic capacitors across the PCB so they could dump that current in short bursts instead of pulling it straight from the supply. The finished 13×28-dot panel runs on a Raspberry Pi Pico 2 W and pushes the simulation at around 40 frames per second, steered by a joystick that changes the direction of gravity inside the sim. A built-in IMU adds a second control mode: tilt the whole panel and the “fluid” pours from one side to the other. Total parts cost, not counting the donor hardware, landed under £500 (about $662), roughly 23 cents per dot.
Build It Yourself
- PCB design and firmware: published on GitHub, tuned for Hanover-brand 13×28 flip-dot panels
- No flip-dots on hand? The same gravity-joystick trick runs on any RP2040 board driving an LED matrix you already own
- Size your capacitor bank to your own dot count and current draw before you solder anything permanently, that’s the step people skip and regret
Read Jacobs’ full write-up and grab the source files from the original Hackster coverage before you start ordering parts.
Frequently Asked Questions
What controls the flip-dot fluid simulation?
A Raspberry Pi Pico 2 W runs the simulation at around 40 frames per second. A joystick changes the direction of gravity inside the sim, and a built-in IMU lets you tilt the whole panel to pour the simulated fluid from side to side.
How much does a project like this cost to build?
Jacobs estimates the total parts cost, not counting the salvaged donor flip-dot panels, at under £500 (about $662), or roughly 23 cents per dot on the 13×28-dot display. The real cost driver is finding usable flip-dot panels secondhand, since they aren’t sold new.
What will I learn if I build something like this?
You’ll practice driving a high-current electromechanical actuator safely (the panel spikes to roughly 50 amps when flipping many dots at once), sizing a capacitor bank to buffer that current, and porting a 2D fluid simulation algorithm (FLIP) onto a microcontroller with real-time sensor input from a joystick and IMU.
