Dot flippers

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

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Seeing that my flip-dot outbreak has infected a few of my respected HAD fellows, I thought it was only fair to invite them here to discuss about these displays, exchange tips and links, and show off our progress using them :-)

Of course, we're not speaking about easy-to-arduinize system such as AlfaZeta's module. It's more fun to design the driver boards ourselves :-)

1. Wild guesses
2. Some progress
3. Actual boards
4. Andere Anzeigen
5. Just Blow
6. The flipping point

  • The flipping point

    Yann Guidon / YGDES12/21/2016 at 01:20 0 comments

    So far I have received two kinds of flip-dot panels.

    • A "PCB" type, where the coil is printed on the board. Very neat...
    • A "wound" type, where the coil is made of enameled copper wound around the magnetic rod. Classic.

    These two have different working points, as measured with a lab power supply:

    • The PCB type starts to flip the dot when about 8V are applied to the coil. Add 0.7V (the unavoidable diode drop) and the LUMINATOR panel needs at leat 9V to operate. The nominal operating voltage is around 12V (compatible with my #YGREC16 - YG's 16bits Relay Electric Computer) but what's surprising is the operating current : the dot flips even down to maybe 20mA (the lab PSU goes in current-limit mode). I expected more... I suspect the PSU's output capacitors to store enough charge to create a current spike, so I'll have to test different configurations. Flipping power: less than 1/4W.
    • The wound type (made in Germany) has a coil resistance of about 16.6 Ohms. The flipping current is around 130mA/2V, which means 3V or 3.3V with the diode. Flipping power: around 1/2W.

    I'm amazed by the power efficiency of the LUMINATOR array. The printed coil is also more predictible and less subject to corrosion. OTOH the german displays are notably oxydized and several dots are damaged. I expected only one line (out of 19) to be unusable but mishandling might have occured and I can't get the 17 lines I wanted (16 data lines + parity, to spy on the memory).

    Conclusion : if I give up on the extra parity line, the LUMINATOR is the best choice for my relay computer project. Thank you @Shaos for your precious help :-)

    Now I have to examine the pulse characteristics...

  • Just Blow

    Yann Guidon / YGDES12/20/2016 at 21:51 0 comments

    I received a couple of different boards from Germany and wanted to test them, without and driver. I'm tired and lazy so I just blew over it :-D

  • Andere Anzeigen

    Yann Guidon / YGDES12/09/2016 at 23:46 2 comments

    Good news, european fellows : the magic of eBay has struck again :-D Look at these beauties:

    Like the previously seen LUMINATOR arrays, they are 28 dots wide, but 19 dots high instead of 16. That's why I took the display with the three broken dots : it's cheaper and I don't need the bottom 2 rows. That's 17 lines and I can still show the parity bits :-)

    OK I also ordered the pristine one. But the seller still has other modules for sale at the time of writing (the 2 last links). Watch the seller in case more became available...

    The shots of the back show the pairs of steering diodes and the matrix is very simple so I expect no surprise. I can un-socket the IC and do my things...

    Unlike the LUMNATOR the PCB doesn't implement the magnetic coil, so I'm curious.

    Ô the things I could do with them... ;-)

  • Actual boards

    Shaos11/30/2016 at 06:51 6 comments

    I've got actual boards today:

    Close look from the front:

    And the back:

  • Some progress

    Yann Guidon / YGDES11/30/2016 at 03:27 0 comments

    @Shaos got boards !

    He also shared some informations he dug, such as we learn more details about flip voltage (10-15V) so it's right in my range of +/-12V (though there is one more diode drop, which could be reduced with a Schottky).

    I'm also curious about the following remark : ".... there is little risk of a flip dot being energized for more than a few hundred microseconds"

    I don't know the cycle time of my machine but I was anxious that the pulse would be too short. I thought a dot would need a pulse that would last something like 100ms but Harrison implies that it's in fact shorter. Given that the RES15 relays have a propagation/latency of around 3.5ms, it's actually a good margin yet not excessively long... We'll see !

    Maybe it's a coincidence but has just published a story about modern flip dots screens, the expensive kind...

    Oh and have a look at the gorgeous dots at

  • Wild guesses

    Yann Guidon / YGDES11/27/2016 at 01:23 6 comments

    I don't know when I'll receive my modules but I have found an online source of some Luminator Max 3000 arrays. 16 lines, 28 rows, this is perfect for my system. But how do we drive them ?

    I've found a youtube video that seems to be a very similar model.

    The implication is clear : it's a "typical" array, almost.

    But there is a bit more than that, when looking closer.

    We can see on the backside that there are 2 diodes per dot. So it's not a typical array like with LEDs. The solenoids must be driven in one direction or another, which is not the case with a classic diode array.

    I have found an interesting description there but I have independently come up with a little different approach that is suited to relay technology.

    The +/-12V symmetric supply is already used for the DRAM bus of the #AMBAP: A Modest Bitslice Architecture Proposal but there is a difference : the column select switches to 0V, not -12V (which is required by the electrolytic polarized capacitors). The data driving circuit is shared with the data bus, but a separate column selector must be wired. A couple of diodes must also be added for each data line.

    For semiconductor technology, it's quite simple as well : a high-side PNP or P-FET and a low-side NPN or N-FET will be enough, no need of a diode.

    Of course, it must be tested.

    PS: the diodes are not strictly required, if you drive one end with a high-side to +Vcc and the low-side to -Vcc. However the above circuit diagram requires the diodes because I get the data directly from the write bus of AMBAP. It already drives the data line at these levels to recharge the DRAM's capacitors. Without the diodes, the current wouldn't be correctly steered...

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Simon Merrett wrote 04/02/2017 at 22:18 point

Are there any attempts to make flip dot arrays in open source hw? It seems like a pcb coil is fairly achievable. A coil winding mechanism could be simple to make in order to scale up the classic approach. I've been toying with a quad arrangement of dots actuated with a micro servo - they cost in the $1 order of magnitude in quantity and I have proven you can make a satisfying flip motion using a magnetic coupling. Unfortunately I haven't been able to make a mechanism that accommodates 2^4 states over a 180° servo throw, so I could only do a pair of dots per servo at the moment. 

  Are you sure? yes | no

Yann Guidon / YGDES wrote 04/02/2017 at 22:21 point

I have strictly NO idea...

If you do anything in this domain, keep us informed please ;-)

  Are you sure? yes | no

Simon Merrett wrote 04/02/2017 at 22:25 point

Ok, will do, although I'm probably slightly overcommitted at the moment. Can't wait for updates/next log on this project!

  Are you sure? yes | no

Dylan Brophy wrote 04/01/2017 at 21:28 point

I never knew this type of display existed! So cool!

  Are you sure? yes | no

Yann Guidon / YGDES wrote 04/01/2017 at 22:12 point

Now you will look closely around you, you might notice a few, before they are all replaced with ugly shiny LEDs :-D

  Are you sure? yes | no

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