Dmitry Dmitriev's Arduino-Powered Control Unit Gets Vintage Flip-Dot Displays Ticking Once Again
Rather than mess around with controllable polarity, this clever controller simply times the flips of an AC supply.
Maker Dmitry Dmitriev has repurposed six vintage FOK-GYEM flip-dot displays into a fully-functional clock, doing away with the traditional complexity of manual voltage polarity control by using alternating current and just the right timing.
"At the beginning of the project, we had six flip-dot blocks from a 50-year-old clock that had previously been installed at the post office," Dmitriev explains. "The control unit has not been preserved. Controlling a flip-dot pixel usually requires changing the polarity of the input voltage. In order to change the polarity over tens of pixels, a complex circuit is needed. We tried to simplify this process by using alternating current."
The idea is, indeed, simple: to force the vintage displays to update their pixels, which are physically-moving flaps marked in a bright color on one side and black on the other, usually requires a circuit that can control the polarity of the voltage being sent. In Dmitriev's approach, that's not required: a standard alternating current (AC) voltage is used in its place, with the control system just timing its own signals for when the required polarity is present.
"By turning on the desired blinker, we switch opto-triacs U3-U6, and the polarity of the signal is selected by one of the opto-relays U1-U2, connected through diodes D3-D4," the maker explains. "All that remains is to apply alternating current to the block for one period and a half-wave of the required polarity will switch the selected blinkers."
While the resulting circuitry required to control all six displays requires a number of opto-triacs and a cascade of shift registers, the components are all available at a low cost — and a simple Arduino microcontroller is enough to drive everything and turn the salvaged displays back into a functional clock once more.
More information on the project is available on Dmitriev's Hackaday.io page, with source code and schematics published to GitHub under the reciprocal GNU General Public License 3.