[Mike Harrison] has an upcoming challenge which can mix a lot of flip-dot shows salvaged from buses. [Mike] thought he knew how these items labored, and had a prototype PCB made instantly. However whereas the PCB was being manufactured, he began digging deeper into the flip-dot’s flipping mechanism.

As he dismantled one of many flip-dots, he realized there was quite a bit occurring underneath the hood than he realized. The dots are bistable — staying put when energy is eliminated. That is achieved with a U-shaped electromagnet. The polarity of a driving pulse utilized to the coil determines which method to flip the dot and saturates the electromagnet’s core within the course of. Thus saturated, every dot is held within the desired place as a result of the black aspect of the dot is produced from magnetic materials. However wait, there’s extra — on additional inspection, [Mike] found one other everlasting magnet mounted within the base. He’s not sure, however thinks its job is to hurry up the flipping motion.

Apart from curiosity, the rationale [Mike] is finding out these so carefully is that he desires to construct a unique driver circuit to have higher and quicker management. He units out to higher perceive the heart beat waveform necessities by instrumenting a flip-dot and ranging the heart beat width and voltage. He determines you will get away with about 500 us pulses at 24 V, or 1 ms at 12 V, a lot better that the ten ms he initially assumed. These waveforms end in about 60 to 70 ms flip occasions. We particularly loved the slow-motion video evaluating the flip at completely different voltages at 16:55 within the video after the break.

[Mike] nonetheless has to give you the optimum driving circuit. He has tentatively has settled on a WD6208 driver chip from LCSC for $0.04/ea. Subsequent he’ll decide the optimum method to scale this up, deciding whether or not going for particular person pixel management or a a number of sub-array blocks. There are mechanical points, as nicely. He’s going to must noticed off the highest and backside margin of every panel. Reluctant to unsolder the 8500+ joints on every panel, his present thought is to solder new controller boards straight onto the again of the present panels.

This video is a must-watch for those who’re engaged on drivers in your flip-dot show challenge, and we eagerly look ahead to any future updates from [Mike]. We additionally wrote about a challenge that repurposed comparable panels a few years in the past. There are a number of particulars that [Mike] hasn’t found out, so if you already know extra about how these flip-dots work, tell us within the feedback beneath.