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
7. More on youtube
8. Dots from Hannio
9. Some more videos
10. Progress in DIY flip dots!

  • Progress in DIY flip dots!

    Simon Merrett07/07/2017 at 11:17 9 comments

      UPDATE 11/07/17
      It's very late here so I'll just show the picture - a nibble of pager motor flip dots, driven by a single pin each from an Arduino Uno, with a 2.5V rail provided by a low value (and hot) resistor divider:
      Not perfect by any means but nice to see the beginnings of an array.


      I'm a new member on this team but have been following the project for a while. My goal is purely for interest, rather than a specific project I need to make. I'd love to see these displays accessible for more people. So far I see three barriers to wider adoption that I think we can reduce:

      1. Mechanical. To make these, you usually need to wrap a lot of wire coils. You need a decent low friction pivot and you need to make dots and frame elements repeatably and in quantity. When you scale all that up, making a usable array becomes hard work and not really worth the effort.
      2. Electronic. These displays often need positive and negative voltages. They also need control circuitry that can handle these rails and this can result in H bridges, mosfets and optoisolators, not to mention multiple IOs from the controller IC for each dot or pixel. Multiply that by the pixel count of your array and the control electronics
      3. Price. This is perhaps a consequence of the first two problems but often time is less critical to hobbyists and non-professionals, who are perhaps more sensitive to price.

      So I've been trying to think of a way to improve in these three areas. The main idea I had was to use a micro servo (cheap, single 5V rail) to drive four dots or two dots (minimum IO pins per pixel) by rotating a notched wheel underneath the grid of dots. These notches would engage with a lever for each dot that would rotate 180° and magnetically couple to the disc of the dot itself. Like this: The lever pivots on the paperclip axel you can see in the bottom left. The motion of the "flip" and short settling oscillations are not conveyed well in this GIF but I found the action very pleasing and it produces a quiet fluttering sound which is a nice benefit.

      The problem I was struggling to overcome with this arrangement was that to make this work with one servo creating all possible combinations for four dots, the 180° range of servo rotation would be have to divide into 16 to provide every possible permutation of four dots' settings (2^4) or divide into 4 (2^2) for two dots per servo. I couldn't get over this stumbling block as two dots per servo didn't really seem worth the effort to make each mechanism and four dots seemed too hard; the for a 25mm dot the radius of the notched wheel would be 50mm and resulted in around 4-5mm circumference between settings. That's not much distance to transition the lever mechanism from one position to the other and I put the idea on hold.

      Someone else's bright idea

      A few days ago @Benchoff posted on the HAD blog about [sjm4306] using pager motors for a mechanical segment display (for a clock in this case). He encounters an issue of segments not being able to be arranged near each other without careful planning of the layout to ensure motors didn't end up being inserted and clashing. I immediately ordered some of the pager motors he used as I thought they could produce the magnet rotation that the lever of my first design provided.

      Then I couldn't wait. I have some small pager motors already but they are the flat round type which are fully enclosed: I decided to see if I could break out access to the rotor and using small pliers prised off the cover (the sides and top surface in the picture above). I forgot to take a picture of the inside before I glued stuff onto the rotor but there is a cam-shaped rotor (eccentric mass to produce vibration) with two tiny copper wire coils mounted in it. On the underside of the rotor there is a commutator with around 6 plates (looked like more than 4). A pair of "brushes" or spring contacts supports the rotor from the stator and there's a tiny pin of an axel that keeps the rotor in place. There...

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  • Some more videos

    Yann Guidon / YGDES06/05/2017 at 01:00 0 comments

    Flip dots are really a fun, useful, easy, simple technology that can get more people interested in electronics and electronic data processing :-)

    Now if anyone wanted to make a purely electromechanical TETRIS game ?....(I wish there was a way to read back the position of the flaps)

  • Dots from Hannio

    Yann Guidon / YGDES05/15/2017 at 22:51 5 comments

    See the latest updates at the bottom :-)

    The last log More on youtube introduced me to the tiny german webshop of

    I couldn't resist and bought two kinds items:

    The pros:

    • brand new, at least for the 1×7 modules, so unlike eBay you don't gamble...
    • The 1×7 can be organised at will for any geometry, with a pretty good price.
    • convenient payment with paypal
    • fast delivery (5 days from order to delivery in France) for reasonable price

    The cons:

    • packaging... 1/4 of the 1×7 were damaged. One of the flaps is missing from one 16×24 and I don't know how to repair it (no spare for this very unusual part). I don't blame the sender because the carboard box seems to have been crushed and/or "inspected". The crush has damaged the 16×24's connectors...
    • website only in German, not easy to contact the seller...

    some of the 1×7 needed repair but that was easy.

    Overall: very positive, good quality, good price/dot, I could easily repair most of the 10mm dots and the connectors of the 16×24 modules can be desoldered/replaced. And speaking German helped me again :-D

    And since my last order, there is a new model : 16×28 module with controller board ! Who wants to try it ?

    Update 20170516 :

    The coil resistance is measured at 19 Ohms. However some resistances have been measured as "infinite" and the thin, fragile wire was damaged during shipment. I'll have to check how many need repair and who many survive (anybody wants to help manually check 350 coils ?). The really broken ones will serve for surplus/replacement discs and will be cut in smaller lengths (because 7 is not a very convenient size to create 16 or 18-wide displays).

    The resistance of 19 ohms is a bit higher than the 16.6 ohms of the other german panel I have so I expect slightly different flipping characteristics, but not far from 130mA/2V : 100mA@2V is better, indeed (but quite slow). However, higher current in needed to overcome the hysteresis of the factory-set dots : 2.5V/125mA is a good bet. It works well and fast at 3V. Direct drive is easy with a 3.3V power supply. Adding the diodes' drop (2×0.8V), the dots are suitable for matrices running with 5V.

    I must still characterize the 16×24 array, which uses a single-coil structure...

    June 20, 2017:

    A new batch with mooooore flip dots ! I have accumulated about 1500 dots in original packaging. The shipping was a bit turbulent but less problems than before. The store owner will stuff the next packages with bubble wrap.

    Another 16×24 array completes the others, so I might be able to also create a 24×32 or even 24×47 display (the last column has a missing flap).

    And following my advice, the site is now available in english too !

    The stock of stripes is slowly running out so don't wait to get yours :-P

  • More on youtube

    Yann Guidon / YGDES05/10/2017 at 02:56 0 comments

    Dave Jones of EEVblog got some coiled dots :

    And this video made me discover where to buy these 7×1 modules and 16×24 modules :

    Now here is a very interesting store in Germany :

    7×1 FlipDots

    The 16×24 looks great !

    They also look smaller than the usual display, which is great for graphics displays...

    16×24 flip dots module

    Has anybody else seen this model before ?

  • 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!

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

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

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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

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