Close

A different driving strategy

A project log for Dot flippers

or "flip dotters" if you want. Let's just talk about flip-dot/flip-disc displays and projects using them :-)

MuthMuth 02/18/2021 at 10:571 Comment

It's been quite a while I'm looking for displaying animation on a flipdot matrix. There is of course the impressive projects from AlfaZeta of Breakfast, but they are very expensive.

When I was looking closely to these matrices, I could guess they drive them by tiles, 8x8 or larger.

After playing a bit with raw dots, I observe that a charged capacitor of around 10uF at 16V, discharged directly into the dot's coil, is enough energy to make the dot flipping correctly. There is something to dig here, so I made a circuit with the coil in series with a capacitor, as shown below. One side is grounded. If you apply a voltage on the other side, the capacitor will charge, with a current flowing through the coil in one way. If you discharge the capacitor by grounding this same side, the current will flow the other way.

Now how to charge and discharge this circuit? With a CMOS, or complementary Mosfet for example. Lets try to simulate this concept in LTspice:

It seems to work, the green line is the current across the coil. Pulses in both directions are generated depending on which input is enabled.

One nice feature of this circuit is only the charge will consume energy, the way back is for free.

I choose a PIC with a handy SPI peripheral, plus two 8bit port. PIC16F15345, and start kiCad.

We can buy flipdots here on Hannio.org. They come in rows of 7 dots, probably because of 7x5 fonts. Using a 4 layer PCB, I manage to fit everything within the flipdot footprint.

A first test program gave me encouraging results:

Discussions

Simon Merrett wrote 02/19/2021 at 07:52 point

Great work! 

  Are you sure? yes | no