Skip to main content
Topic: Flipdot fun (Read 7047 times) previous topic - next topic

Flipdot fun

Hi all,

I've been working on a flipdot project for the past 3 months and wanted to share some of the things completed so far. I think it looks quite good, if I may say so myself ;-)

For those of you who don't know flipdots, these are mechanical discs (black/white or black/color) that flip with a (semi-)permanent magnet which can be polarized in either direction. A large current must be applied to a coil to flip the magnetic field and the disc will flip. Flipdots are available in 1x7 strips and in different sizes and colors. The direction of the current through the coil depends on which direction you want to flip. The current must be kept at 350mA for at least 450 micro seconds for the permanent magnet to reverse polarity.

Preliminary testing is documented in more detail at http://http://www.vagrearg.org/content/fliptest.

The first project was a battery operated 1x7 flipdot strip that could flip at 1flip/s for some time.
[attachment=0]
[attachment=1]
Two AA batteries are used, each 2500mAh types. A small PIC16F1507 micro-controller controls the flip-program.

The hard part was to get the energy out if the batteries. To flip a flipdot, you need quite a bit of energy and some test showed that it needed at least 9V. The high voltage is generated with a step-up converter in current-mode. Step-up conversion using voltage-mode proved to be a very high drain on the batteries (>700mA for several ms) and would not perform well on old(er) batteries. The current mode charges 200microF of capacitance with a 20mA constant current up to 9.1V. This energy is then dumped into the flipdot-coil through a set of H-bridges to generate a characteristic LCR transient curve and that flips the dot. A second step-up converter is used to generate a stable Vcc for the micro-controller and ensures that no brown-out will occur with older batteries.

The system proved to be very robust and the first prototype device operated at 1.5flips/s for over 40 days (>5500000 flips in total).

At last call, I was asked if I could add a USB port on the device. I already had programmed a serial input on the PIC controller (the 16f1507 does not have a usart), so there was no great deal in doing so. An MCP2200 serial-to-USB converter with a mini-B connector was added and a couple of diodes to enable power from either batteries or USB. Finally, with my fingers itching, a PC control program (using QT) was created to control the device when connected via USB. That turned out to be a lot of fun with the ability to define a flip-sequence of choice at max. 40 flips/s.

The entire FlipDemo project is documented in more detail, including schematics and test data at http://http://www.vagrearg.org/content/flipdemo. Please feel free to comment on any part.

Next up will be to complete my 7x7 flipdot modules.

Re: Flipdot fun

Reply #1
I love those dots. Do you have a reliable source for these?

NIce project!

Re: Flipdot fun

Reply #2
[quote author="Sjaak"]I love those dots. Do you have a reliable source for these?[/quote]
Yes, very reliable; directly from the manufacturer of the flipdots. The battery operated device was made on request of the manufacturer :-)

Re: Flipdot fun

Reply #3
[quote author="Bertho"][quote author="Sjaak"]I love those dots. Do you have a reliable source for these?[/quote]
Yes, very reliable; directly from the manufacturer of the flipdots. The battery operated device was made on request of the manufacturer :-)[/quote]

any links to a shop or do they only business to business?

Re: Flipdot fun

Reply #4
[quote author="Sjaak"]any links to a shop or do they only business to business?[/quote]
The link is actually on the PCB as shown above: www.flipdots.com.

I do not know if they do private sales, but I guess they do. However, from what I know, it is quite expensive in low volumes. The other thing is that controlling the dots is easy on its face, but not as easy if you want to have good control and you want to flip them really fast (so that they stick).

The whole reason why I got involved was that our hackerspace (osaa.dk) got two old flipdot based bus-signs as a donation and we wanted to hack them. I've documented that part at http://www.vagrearg.org/content/dotflipctl and wrote a small game as a demo for it. The major drawback of those signs is that they are slow, really slow and effectively cannot do more than 500..1000 flips/s if you are lucky. I wanted to do 25 frames/s on the entire sign and that made me start on small 7x7 modules. See http://www.vagrearg.org/content/activeflipper for my progress so far (need yet to document prototype #2; see www.activeflipper.org for some info on them). My goal is to do a production run of the 7x7 modules if I can get enough people interested. The production costs would be too high if I cannot get up to a reasonable volume.

You are welcome to contact the manufacturer Alfa-Zeta (in Poland). These guys took over the production lines from F-P Electronics some time ago.

Re: Flipdot fun

Reply #5
This looks like a lot of fun Bertho - nice work!

Re: Flipdot fun

Reply #6
i thought i had seen something like this some time ago. they had commercial clock with dots, doing some r&d with the mechanics to make it less noise etc. i can't remember where i read that.

btw, i played the demo video, and i can not hear any noise from the dots flipping?

Re: Flipdot fun

Reply #7
[quote author="dion"]i thought i had seen something like this some time ago. they had commercial clock with dots, doing some r&d with the mechanics to make it less noise etc. i can't remember where i read that.[/quote]
I've seen some "old" stuff being reused, but I have not seen much new products. For that matter, most stuff I've seen is showing "it works", but no further details.

The whole point of these flipdots (IMO) is that they are supposed to make noise... That is one of the funny things. However, when you have a good case, the noise is damped quite well as long as you do not flip too many dots at the same time..

[quote author="dion"]btw, i played the demo video, and i can not hear any noise from the dots flipping?[/quote]

This one makes noise (quite a bit): http://www.youtube.com/watch?v=COwQp3L9IMs

The one with the game (http://www.youtube.com/watch?v=wYpIK0tRCjY) is much more quiet because it is encased and the video is taken from some distance. When we tested the sign we made http://www.youtube.com/watch?v=6AaE531IyeI and that is supposed to make some noise too.

If you do not have any sound, maybe you should turn it on/up? (sorry, couldn't resist)

Re: Flipdot fun

Reply #8
i don't understand. where is the art if you made it with noise? everybody can make that.

Re: Flipdot fun

Reply #9
[quote author="dion"]i don't understand. where is the art if you made it with noise? everybody can make that.[/quote]
The whole point, IMO, is that flipdots make a "flip-sound" and that is just a nice thing. If you want a silent sign, by all means, pack it into a case with dampening.

The "art" for what I made is two-fold. For one, the flipdots run off a battery for 5..6 weeks at 1.5 flips/s. Considering that you need 350mA and 9V, that is a challenge when you want to preserve battery life.

The second "art" part is that I have been designing a module (7x7) that can flip at >30 frames/s or about 1666 flips/s continuously. Furthermore, if you cascade multiple of the modules, each and every one of the can flip at the same rate. The old bus-sign can do (total) about 1000 flips/s. Making a sign out of 7x7 modules makes it flip at 85000 flips/s.

It is a combination of a challenge in design, pressing most out of your hardware and having a lot of fun in the process. Besides, I just like those flipdots ;-)

Re: Flipdot fun

Reply #10
I've been dying to get my hands on some of these. Thanks for the link to the manufacturer! Now to find out if they're in any way affordable.

 

Re: Flipdot fun

Reply #11
[quote author="nickjohnson"]Now to find out if they're in any way affordable.[/quote]
Don't get your hopes up. They are expensive.