Flip Fluid on Flip Dots
An engineer designed custom driver boards to run a real-time fluid simulation on salvaged electromechanical flip-dot display panels.
read it A thorough hardware build log rich with circuit design trade-offs and practical problem-solving for vintage electromechanical displays.
summary
Mitxela documents the technical challenge of running a FLIP fluid simulation on vintage electromechanical flip-dot panels salvaged from old buses. Finding commercial displays too expensive and original drive circuits too slow, the author designed custom KiCad PCBs using cheap motor driver chips. By employing a clever series-capacitor circuit, the design safely delivers high-current pulses to the coils without risking burnout or melting the delicate plastic components. The resulting installation successfully merges fluid dynamics with the satisfying physical clatter of flip dots.
key points
- Salvaged vintage Hanover bus panels required custom electronics because original drive circuits took a full second to update the display matrix.
- The author utilized inexpensive SOIC-8 motor driver chips paired with series capacitors to safely pulse 12V inductive coils without burning them out.
- Power supply voltage drops during massive concurrent current spikes required hardware workarounds, including MOSFET additions for signal current boosting.
who should read it
Embedded systems engineers, hardware hackers, and retro-tech enthusiasts.
discussion warm
consensus
Commenters thoroughly enjoy the meticulous hardware build, discussing the unique visual and auditory appeal of mechanical displays while sharing their own bus-panel restoration stories.
pushback
Some technical debate emerged regarding alternative circuit topologies and whether hot air gun techniques could safely desolder delicate plastic-bodied components.
It is still going to be many amps.
The capacitor circuit has the advantage that could can't mis-drive. If a transistor of the half bridge stays turned on for longer than the msec required, nothing will happen. The half bridge chip (usually) already prevents that both transistors are enabled at the same time. This is great when you develop firmware and might end up with one pin staying high for too long.
With a direct drive, the flip dort magnet wire could quickly burn through if you leave half an amp for too long.
Explains why the series-capacitor circuit is crucial for preventing burned magnet wires when firmware bugs cause control pins to stay high too long.
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