flip-dot display driver

Hey all,

I've got a question about a circuit I want to design, I'll try to explain in short what I'm trying to accomplish.

I've acquired a nice amount of so called flip-dot strips, electromagnetic display units that contains dots with one side colored fluorescent yellow and the other side black.

You can change the state of the dots (and flip them), by applying a 6v pulse and changing the poles to do the opposite (each dot has two pins).

This technique was much applied in the past, for instance in (railway) stations and displays on buses.

Well, my question is, I want to be able to control 720 (90*8) of these dots individually with an arduino. I've read about the usage of shift-registers for controlling large arrays of led's, but in my case I would also need to be able to switch the polarity (+/-, -/+). I'm guessing this would require some kind of h-bridge (and ofcourse I'd rather use one than 720 h-bridges :))

Has anyone got an idea on how to approach this? Any insights are much appreciated!

Yep, do a normal matrix and make sure your row and column drivers are tristate. Row high / column low flip one way, row low / column high flip other way. How many milliamps will each pixel require? Obviously if it’s a few mA this gets easy. 100mA not so much.

I have to ask…WHERE did you get them?

Oh BTW those are 7 dots long, not 8.

I'd love to hear more about this project, as I've been flirting with the idea of using flip-dots in an interactive art installation. I think that the way they move sort of entrances viewers and there's a bit of a classic feel to the whole thing.

EDIT: I've been checking around on the net, and I'm afraid I must echo the poster above, where on earth are you buying the individual strips? I found the site that put up the image you used, but I can't seem to find anybody selling the individual strips. http://www.mckennabrothers.co.uk/flipdot.html

By the way, here's something I found in my searches, so pretty. http://www.youtube.com/watch?v=42hgPLL8IrA

yes, the ones in the image are 7 dots, the ones I have are octagonal shaped (the dots) and 8 long. i've bought them through a polish company called alfa-zeta, they sell lot's more nice electromagnetical goods. macegr, thanks for pointing me in the right direction! I'm not sure yet how much milliamps each pixel requires, I'll have to do some additional testing.

I tried making my own flip dots last year - from scratch - winding the coils, finding the right size magnets, etc. laser cut foamcore and matte board structure. I got 64 of these made before I ran out of steam- guess it was kind of crazy to try but...

I used H-bridges - and shift registers - but wanted to be able to flip more than one at a time so planned to use 8.

http://roypardi.com/flutter/flutter.html

What did those units cost, if I may ask?

Hi Roy,

Nice to see your selfmade flipdot(s)! I actually planned on doing this as well. Do you have some more images of your final application? And did your power supply then needed to be 64amps? (!) The units I bought cost me ? 2,50 a piece.

The photo above comes from a Polish vendor, as mentioned. They refer to a sister site, http://www.flipdots.com/ which is in English. They offer solo dots, strips and bricks, but they don't say how much they cost. They also mention 16x16 RGB LED matrix parts.

Oops, forgot to come back after I found this page. I place a request yesterday, no response yet.

http://www.flipdots.com/EN/contact.html

Nice to see your selfmade flipdot(s)! I actually planned on doing this as well. Do you have some more images of your final application? And did your power supply then needed to be 64amps? (!) The units I bought cost me ? 2,50 a piece.

Google tells me that ? 2.50 = 3.28925 U.S. dollars. Is that all they were?? Geez the hell I went through trying to make my own! (learned a lot though- about shift registers + H-Bridges). The project got side-tracked because I had a big installation exhibit that took all my attention. Still I felt bad about letting it slip away.

My final dots were big - like in the image/video - @ 3" diameter - and black + white, no florescent (big dot on one side, small dot on the other) No video but some stills of the production phase: http://roypardi.com/dots/IMG_2527.JPG http://roypardi.com/dots/IMG_2525.JPG

I couldn't flip them all at once so I planned to flip a row at a time- it fit with the installation idea: these were going to be on the floor and there were going to be two breath sensors (blow on it, etc.) and the dots would ripple to give the impression of wind blowing over water. I had planned to make 1024 of these things... insane... so that they filled a space.

It shouldn't take an amp to flip the ones you have - but I didn't know what I was doing - winding coils and trying to get the magnets right - so it took a lot more current to get them to flip than if someone who knew what they were doing designed them....

It's a cool technology - getting a mechanical/kinetic display result from an electrical/magnetic effect.

Have you taken apart one of the ones you have to see how they are made? I tried to buy some samples so I wasn't reinventing wheels but the company I wrote to never replied.

--Roy

yes, that's what they cost me (note that this was some old stock), but the new ones they offer shouldn't be that far off. did you self-wind all those coils? (some insulated with black tape?). hell of a job! I haven't taken one of my dot-strips apart so far, but the principle seems pretty straightforward, i can make some photo's sometime soon and post them if you'd like, there seem to be two small coils for each dot, and I think one of them attracts the dot (which has a tiny hole punched out on one side), anyway, photo's should be more clarifying.

HOOO!!! Three bucks each? I'll need to find some work under the table for what I'm planning. Has anybody thought of calling up a bus system, finding out where they send decommissioned buses? The lettering on the front saying where it's going is usually a flip-dot system, and it seems you could get three or four panels of the dots at a junkyard for about $50 or less. I'm already tracking down local bus lines and asking questions. Someone in a big city would have no problem finding these parts en masse, and might be so kind to resell them at cost + postage?

yes, that's what they cost me (note that this was some old stock), but the new ones they offer shouldn't be that far off. did you self-wind all those coils? (some insulated with black tape?). hell of a job! I haven't taken one of my dot-strips apart so far, but the principle seems pretty straightforward, i can make some photo's sometime soon and post them if you'd like, there seem to be two small coils for each dot, and I think one of them attracts the dot (which has a tiny hole punched out on one side), anyway, photo's should be more clarifying.

Would love to see some photos and/or a description (might be hard to photograph) of how they are constructed. I found a few things on the web when I was making mine - but nothing detailed or any close up views.

Yes I wound the coils - did a bunch of tests for size and number of layers, size of wire - but it was mostly trial and (mostly...) error since I don't have any sort of electrical engineering background. Tried a sewing machine first - winding the bobbin. That worked pretty great but the bobbin cores are pricey (when you need a lot). Ended up using 1/4" plastic tubing for cores and an electric drill with speed control. Was pretty easy to do- though a bit tedious. That's not black tape on them - it's heat shrink tubing like you would use for wires.

I'm good at fabrication, electrical engineering... not so much ;)

Oh - the bases were laser cut out of matte board and the dots out of foamcore. First time I had used a laser cutter - awesome!

--Roy

here's some more detailed photo's:

thanks for posting the pix. Two coils, eh? What part of the mechanism is magnetized? The dot itself?

yes, each dot has two coils, and the coils seem to be connected as well. Note that one of the two coils is longer on the top, the dots (while in ‘rest’) are always in a little angle. The dots do seem to be magnetized, if I remove some of them they do stick together or repel one another. I wouldn’t be able to explain though why that is, I have little electromagnetical knowledge. what do you think?

Here's a pretty impressive flip dot wall:

http://www.youtube.com/watch?v=LT7nj2Rl4kU

funny - there are a lot more google hits for flip dot suppliers than there were a year and a half ago when I was starting with my home made ones.

a flip dot watch!!: http://mechanicaldigital.com/mechanicaldigital/

You've probably already hit the Wikipedia entry: http://en.wikipedia.org/wiki/Flip-disc_display

I had an illustration that explained the several methods that are commonly used but I can't find it now.

--Roy

that's a real nice example (the wall). that illustration you mention would come in real handy for making your own, if you ever come across it, please post it. I have another flip-dot unit for evaluation, which has a 6cm diameter. before returning it to the company i'll make some photo's of it. the technique used in this one is actually quite similar to the ones you've made yourself.

I'll dig around for it. Will be interested to hear how you make out with driving these things. Maybe I'll get inspired to go back to my home brew project :)

Hi Everybody,

first of all I would like to say HELLO. I recently 'discovered' Arduino as a wonerful prototyping tool and since I was looking for flip-dots driver, I landed here.

I would like to check if there are any results of this discussion and also offer support inregards to flipdots. I have been working with this technology for more then 10 years and still using it in many projects. I will be happy to share experience here.

Hi! Welcome to the Arduino - it is fun and you'll find lots of support here.

I never got further with my DIY flip-dots than what I mentioned earlier in this thread. My problems were more with the electromagnet elements of the flipdot - my homemade ones were grossly inefficient and took a lot of power to run. I would imagine that commercial ones are much better - I just didn't have any and the ones I found for purchase were $$$.

Driver-wise, it isn't hard to multiplex outputs to control a bunch of dots but a lot depends on their current draw and how many are flipped at once.

What sort of project are you working on?

--Roy