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The dots are so delicate, with tiny magnet wires and soft plastic that can melt, that it has to be done very carefully. Even with the very best desoldering equipment it would take forever.
Put a hot air gun on the back of the board, and they'll either just drop out or do so with a small poke of the pins.
Care to post a rebuttal? This is a standard practice. I've scavenged many parts this way.
The plastic is likely the problem there. It's quite easy to melt the plastic on parts like this and if it's thin, has a low melting point, and needs to function mechanically it's likely to do more damage than with your average chip package.
Might not be so bad considering that all the plastic is on opposite side of fiberglass board. When desoldering connectors or smd chips, it's often hard to avoid directly blowing hot air at the plastic bits. That's not the case here. Having dots grouped in rows of 7 makes things a bit more challenging. As it means heating up larger area and increase chance of them getting stuck even when all the solder is molten.
But the theory would have to be tested and there aren't many people with so much flipdot panels that desoldering is a major concern. And ones who have few some don't want to risk it. So bulk processing techniques are likely underexplored.
I have recently resurrected one from an old bus — https://www.bobek.cz/buse/
FYI: the videos on your site do not work for me, requesting them only returns LFS metadata:
Instead of using capacitors ... why not use a negative supply rail? Then you can switch the direction of the current in a coil using only two transistors.
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.
True, but you can program a controller such that this condition does not happen (modern microcontrollers have watchdog timers).
A bigger advantage of the capacitor approach is that you save power (though you could handle that centrally).
A downside of the capacitor approach is that capacitors can slowly leak, but for the application that does not matter much, I suppose. It just has to look nice.
This is how the gas valve driver in your heating boiler works - there's no way anything can actually cause the valve to stick on because it's driven through a capacitor. The microcontroller pulses the valve signal at a few Hz, and it effectively works like a charge pump.
If the output sticks low, no biggie, it's low, the valve is off.
If the output sticks high, no biggie, the drive capacitor will charge in a second or so and pass no more current to the pump capacitor, which will discharge and shut the valve.
Quite often you see solenoid drivers that avoid that with PWM. The airbag driver pack in my old Range Rover does this, as did the Hydractive suspension controller in my old Citroën. In the Citroën the microcontroller directly drove a Darlingon transistor to turn the solenoid on to open valves in the "cross feed" pipes in the suspension. Because that needs to switch quickly against a high pressure hydraulic feed, it needs a lot of current, but because "soft mode" with the valves open is the normal mode for the suspension with the solenoid energised you couldn't leave that current on for a long time.
So what it did was it pulsed the solenoid on for about 250ms and then pulsed it at 50Hz or so, audible as a faint buzz under the car somewhere when everything else was off and clearly audible at certain frequencies on Long Wave radio while driving - very useful for diagnostics! You'd hear the buzz drop out and come back as it switched from soft to hard mode when you threw it around corners.
Similarly the airbag driver module for the Range Rover uses six bloody great big MOSFETs driven by a surprisingly complex analogue circuit with an opamp and a couple of transistors to pulse the solenoid on for 100ms or so and then pulse it at 30% duty cycle at some high frequency.
The valves are held closed by air pressure so they need that initial whack of current to open them, but then they can be held by far less current - well, 30% of the normal current, I guess - once the return spring and air pressure has been overcome.
This is the first time I've seen this mechanism described! I had to reverse engineer my oven control board because the transistor in this scheme died and after staring at the capacitor and diode for a minute it finally clicked, metaphorically, and literally, after I changed that transistor.
What's this circuit called?
Not sure, to be honest. It is basically a charge pump though.
He mentions in the video and in the article Breakfast Studio and I happened to watch a video of one of their panels on an unrelated YouTube channel. I've skipped ahead to when the video has the panel. (there is also a cool egg just before that point in the video) it's only about 5 seconds.
https://youtu.be/2fRx64OTAeI?si=FJDW3OGYLRK0rYox&t=681
It's really cool to see some innovation in flip-dots and their colours, seems really quiet too. Shame these things cost an arm and leg and are massive, something like this in your house would look great at like 1/5th scale.
I'm always amazed by the precision work this guy does. My only nit with this article was he didn't link the Eurovision entry:
https://youtu.be/I0tqgGVQkew
What exactly is the connection between this article and the video?
The performer in the Eurovision video is "Look Mum No Computer", aka Sam James Bartle, who runs the museum that was the source for the flip-dot panels. There was a brief call-out near the start of mitxela's video.