Making the Flippin' Thing Flip

A project log for The Big Flipper - Four Letter Word In Flipdots

What do you get if you mash up a word association database with some flipdot highway signs pulled out of a bin?

Tom HarrisTom Harris 05/28/2021 at 11:410 Comments

I should say how to make a panel flip. If you look at FredericL's project and watch Lansing Maker's Network excellent video on the Flipmaster9000(!) on Youtube then you will know all about how they flip.

So you will see that they are wired in a matrix of one column connection, and two connections for each row, which I call H & L. Current will only flow into the H row connection (so positive DC to H, negative to common), or flow out of the L connection (so negative DC to H, positive to common).

I now had to identify the row and column connections. On the back of the panel are a 40 way header marked COLUMNS and a 34 way marked ROWS. I did some continuity tests and noted that the column pins are commoned 1 through 8, 9 through 16, up to 32 through 40. Pins 1 &2, 3 & 4, etc are commoned on the row pins. Now I set a bench power supply to 30V, current limit 250mA and started poking current through the panel. I guessed that this current could not damage the panel provided that I did not keep it connected for longer than a fraction of a second.

What I found surprised me, neither the rows or columns are in sequence. Probably this was done as the PCB for the panel is single sided, so the designer didn't want any wire links. Also the row L connections set (dot visible) some rows, and clear (hide dot) others. Again this must have been done to make the PCB easy. But it complicates the driving, at least as it will be done in firmware that will be easy.

Anyway, here's a table of connections. Columns are numbered from the left 1..5 and rows numbered down 1..7.

1..8: C2

9..16: C1

17..24: C3

25..32: C4

32..40: C5

1, 2: R7L (clear)

3,4: N/C

5, 6: R7L (set)

7, 8: R6L (set)

9, 10: R6H (clear)

11, 12: R5L (clear)

13, 14: R5H (set)

15, 16: R4L (set)

17, 18: R4H (clear)

19, 20: R1H (set)

21, 22: N/C

23, 24: R1L (clear)

25, 26: R2H (clear)

27, 28: R2L (set)

29, 30: R3H (set)

31, 32: R3L (clear)

33, 34: N/C

An example: to set dot on row 3, column 2: positive on R3H, negative on C2. To clear it, negative on R3L, positive on C2.