[HN Gopher] Open source "split-flap" mechanical display
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Open source "split-flap" mechanical display
Author : deeyago
Score : 277 points
Date : 2021-04-19 03:02 UTC (20 hours ago)
(HTM) web link (github.com)
(TXT) w3m dump (github.com)
| mhb wrote:
| See also: https://125.stanford.edu/monument-to-change-as-it-
| changes/
| sva_ wrote:
| Frankfurt airport has a huge split-flap display to show
| departures[0]. I love looking at it changing the data, and hope
| they'll never replace it with a digital one.
|
| [0] https://www.youtube.com/watch?v=cj32w5z81Ak
| rjsw wrote:
| The sound it makes lets you know when something has changed,
| you don't need to keep looking up from whatever else you are
| doing.
| axolttl88 wrote:
| They were installed as useful & beautiful features in the
| Qantas First Class lounge at Sydney International Airport, and
| are much loved:
|
| https://theluxurytraveller.com/2019/03/review-qantas-first-c...
| jcadam wrote:
| Still? Good to know :) Last time I went through Frankfurt was
| back in '06.
| gorgoiler wrote:
| Fantastic.
|
| Glyphs can be loaded in an arbitrary order. For a given corpus
| (e.g. city names, American English digraphs) how does glyph order
| affect the time taken to update the display? Is there an optimal
| ordering?
|
| If your display could accommodate 5% more glyphs, which would you
| add and why?
|
| _(With apologies to anyone revising for an exam this summer.)_
| grishka wrote:
| You can only flip in one direction, so the time taken to update
| is entirely dependent on the previous state. Worst case you'd
| need to display the previous character (B -> A for alphabetical
| order) and would have to flip through the entire alphabet to
| get to it.
| nine_k wrote:
| > You can only flip in one direction, so the time taken to
| update is entirely dependent on the previous state. Worst
| case you'd need to display the previous character (B -> A for
| alphabetical order) and would have to flip through the entire
| alphabet to get to it.
|
| This only applies if you have only one copy of each letter.
|
| You can consider having more copies of frequent letters mixed
| into the stack, if the stack's thickness allows.
| eurleif wrote:
| Wouldn't that only help with the average case, not the
| worst case? Either you have multiple copies of every
| character (in which case you're still flipping through the
| same number of characters as the original stack), or some
| characters don't have duplicates.
| danohuiginn wrote:
| Suppose you are optimizing for the fastest average time
| to display a complete word/phrase. That means you will be
| limited by the slowest letter in each word. But the
| letters are flipping in parallel, which means you can use
| the time waiting for the slowest letter to move the other
| letters to an optimal display.
|
| So have the alphabet ordered in descending frequency. But
| put a second block of the most common characters half-way
| through. For each word you first calculate the slowest
| letter, which gives you a 'budget' of how many flips you
| will take. Then each letter uses that budget to get to
| the optimal location of the character it needs to
| display, probably as early in the alphabet as possible.
|
| If you know which word is being displayed _next_, you can
| also try to get into the best position to move to in
| preparation.
|
| The ideal alphabet ordering might be different depending
| on position in the word -- for instance, some letters are
| more common at the start of a word. And you could think
| about digraphs, taking advantage of Q usually being
| followed by U.
| agys wrote:
| We made a small project with all the 6 letter words from the
| Italian dictionary (as an homage to the inventor and producer
| of the split flap display: Solari from Udine) ordered in a way
| to produce "the least effort".
|
| https://vimeo.com/250121964
| adkadskhj wrote:
| I wonder how easy and cheap i could make these? Would be neat to
| slowly grow a stack of these on the wall with some Pi controller
| and feed Wifi messages to it.
|
| Not sure why i like it, but i do.
| huhtenberg wrote:
| > _laser cut enclosure_
|
| Had a quick look and the cheapest laser cutter appears to be
| around $400. The next one is $1500 and then the price just keeps
| on climbing.
|
| Any first-hand experiences with laser cutters? An option suitable
| for an (occasional) hobbyist use, but not a total junk either.
| pault wrote:
| You can send your designs to ponoko for small batches. Much
| cheaper than buying a laser cutter unless you plan to scale up.
| theodric wrote:
| I bought a 50*70cm "60"-watt unit online for about EUR2000
| shipped. It is the size of a chest freezer. It works reliably,
| except that if you don't power it up with the laser armed, and
| instead flip the safety switch after power up, it will not fire
| the laser. I had one Hall effect endstop fail, but everything
| apart from the enclosure itself is COTS commodity stuff, so I
| just got a pack of new endstops on eBay and fixed it. Cooling
| with an Ikea tub full of water, vent with a hose out the
| window.
| fortran77 wrote:
| We need to vent our laser cutter to the outside. There's also
| considerable danger that what you're cutting catches on fire,
| so they need to be supervised. It's not just the cost of the
| machine--they're not just "plug and go"
| unionpivo wrote:
| Stay away from anything cheaper that 1k at the moment.
|
| Generally speaking, for cutting anything above paper or balsa
| wood, you will need module that costs around $500, higher power
| modules need decent power supply.
|
| There are some laser cutters from china that claim to have such
| power for less, but there is not jet "consensus" on any of DYI
| forums/reddit's that any of them are good jet.
| [deleted]
| leoedin wrote:
| My local makerspace has a really good laser cutter which
| members can use. It works well for that kind of usage as
| there's not too many ways you can kill it or yourself.
|
| Generally cheap machines have compromises which mean more work
| for you - less reliable, less accurate, weaker laser, worse
| software - all of that means a lot more trial and error, a lot
| more burnt material and a lot more stuff you just can't do.
|
| If you want to laser cut thicker materials, but only
| occasionally, you'd probably find it much more cost effective
| (and low effort) to either outsource or find a makerspace which
| has a decent machine. Laser cutting is quite easy to outsource
| as it is very easy to fully specify what you want (2D drawing +
| material specification is all you need).
| thechao wrote:
| Do you have a suggestion? I feel like the last time I looked
| into laser cutting, it was either SEOd hits that were _crazy_
| expensive or shops that looked dodgy. Nothing in-between.
| NathanielK wrote:
| For home gamers, keep in mind the price of the machine is only
| one part. Large laser cutters are expensive to ship (from
| china), and take up a big space. Most materials will also
| require adequate ventilation.
|
| As others have suggested, jobbing it out or joining a
| makerspace is often the best choice for occasional use.
| anonu wrote:
| I've looked into buying ready-made solutions. Vintage split-flap
| mechanisms go for close to $1000 per character on eBay. There is
| a company I found in China that manufactures these, but its still
| around $300 or so per character. Displaying a tweet would cost
| close to $100k after shipping, etc...
| pg_bot wrote:
| https://shop.vestaboard.com/products/vestaboard?hsCtaTrackin...
| aliljet wrote:
| I've long hunted for split flap modules on aliexpress and I know
| folks who buy old train boards to get these modules. I wonder if
| there's someone out there scaling up the manufacturing? I'd love
| to buy modules at under the DIY ~$50 mark and build cool stuff at
| home!
| raverbashing wrote:
| Airports in the 80s/90s were all about those displays
|
| The sound of Flap flap flap flap flap still in my memory
| singularity2001 wrote:
| someone make an ebook reader of this (miniaturized of cause)
| tartoran wrote:
| The randomness factor is quite mesmerizing, each flap search
| ending at a different timing along with the mechanical aspect
| make this a very fun thing to watch. Old tech was so cool..
| abetusk wrote:
| Scott Bezek has a great video on "How a Split Flap Display Works"
| [0].
|
| He also sells blank "flaps" on Tindie [1].
|
| The documentation on how to build the Split Flap is also really
| awesome [2], including how to cut your own flaps [3].
|
| I've been following this project for a while. It's pretty
| awesome. I estimate about $10 per character (as opposed to the
| $180/character (!!) another poster mentioned through Alibaba),
| with a large portion of the cost being the custom cut "flaps" (in
| small quantities). It seems like the cost could get in the $2-$4
| range per character but I couldn't figure out how to do it
| without a significant amount of labor involved in cutting the
| flaps.
|
| FYI, there's also a company called Oat Foundry that sells large
| split-flap displays [4]. I seem to remember the cost being in the
| $10k+ region but I don't see a price and I could be way off base.
|
| Oh, interesting, I see Vestaboard also has a (smaller) one for
| around $3k [5].
|
| [0] https://youtu.be/UAQJJAQSg_g
|
| [1] https://www.tindie.com/products/scottbez1/blank-split-
| flap-d...
|
| [2] https://github.com/scottbez1/splitflap/wiki
|
| [3] https://github.com/scottbez1/splitflap/wiki/Cut-flaps
|
| [4] https://www.oatfoundry.com/split-flap/
|
| [5] https://shop.vestaboard.com/products/vestaboard
| murderfs wrote:
| > I've been following this project for a while. It's pretty
| awesome. I estimate about $10 per character (as opposed to the
| $180/character (!!) another poster mentioned through Alibaba),
| with a large portion of the cost being the custom cut "flaps"
| (in small quantities). It seems like the cost could get in the
| $2-$4 range per character but I couldn't figure out how to do
| it without a significant amount of labor involved in cutting
| the flaps.
|
| Laser cutting a bunch of sheets at once could be one option,
| but material selection might be a problem: PVC releases
| chlorine when laser cut, which will do all sorts of horrible
| things to optics/the meatbag operating the machine. Maybe a
| cutting plotter will work, since you're using really thin
| sheets?
| abetusk wrote:
| Laser cutting is straight out for the hobbyist, because of
| the chlorine, as you correctly point out. I think the way to
| do this is either with a CNC or with some die punch solution.
|
| Doing a single cutout of PVC with a CNC would be fine, but
| doing 40x23x7 is probably not.
|
| Doing a die punch is maybe possible but I don't really know
| how to create a custom punch and what tooling to use.
| jiveturkey wrote:
| > Laser cutting is straight out for the hobbyist, because
| of the chlorine
|
| Just don't use PVC blanks.
| atrus wrote:
| It's too bad there isn't a bigger market for this, steel
| rule dies aren't too expensive to get made. And used
| clickers are pretty cheap too.
|
| But only if you were doing a bunch of signs!
| mschuster91 wrote:
| > Laser cutting a bunch of sheets at once could be one option
|
| Use a waterjet cutter instead. You'll have some issues with
| microplastics in the water, but these can be filtered.
| abetusk wrote:
| Show me a water jet cutter that's priced at the hobbyist
| level (and isn't a full time job to upkeep) and I'm there.
| jiveturkey wrote:
| I don't understand. Just send it to a service. You don't
| make your own PCBs do you? There's lots of things a
| hobbyist cannot do in-house, and even if you can just
| make far more sense (at hobbyist scale) to contract out.
|
| There is the wazer, but it doesn't live up to its hype.
| mschuster91 wrote:
| A lot of hacker spaces have waterjet cutters, they're not
| _that_ expensive if you 're a collective pooling together
| funds.
| techdragon wrote:
| This is just awesome on so many fronts. I love the automatic
| update of the BOM using GitHub actions, it's such a nice touch.
| nonninz wrote:
| A nice coincidence, this was on my homepage of Reddit this
| morning: Smart flip clock with weather tutorial [1], [2]
|
| It looks like in this other project they just 3D print
| everything?
|
| [1]
| https://old.reddit.com/r/functionalprint/comments/mtq0k8/sma...
| [2] https://github.com/barlowtj48/flipclock
| argvargc wrote:
| Genuine question: what are some practical advantages of a split-
| flap display over, well... any other kind of dynamic character
| display?
|
| The only two I could think of are:
|
| - they don't emit light, so maybe there could be some kind of
| light-sensitive situation where this would be required (though in
| that case e-ink would surely surpass it).
|
| - the sound passively-alerting those present to updates. It's not
| obtrusive or attention-getting like a bell or spoken
| announcement, so only those wishing to notice the updates can
| listen for the sound, while others can go about their business
| unperturbed.
|
| Anyone know of, or could imagine any others?
| aubergene wrote:
| The contrast is very high, so easy to read in bright sunlight
| agys wrote:
| Readability and ultra low energy consumption (plus: they are
| awesome and produce a soft sound like a distant waterfall).
|
| Also, contrary on what I have seen on LED matrices or other
| RGB/pixel based displays: they won't display advertisement
| which otherwise manages to sneak in - too close to information.
| 0xffff2 wrote:
| I wonder how their energy consumption actually compares.
| Electric motors moving relatively heavy physical cards is far
| from free. I wouldn't be surprised at all to find that an
| eink display beats the pants of of a split flap display in
| terms of energy consumption, but I don't have the necessary
| equipment to test it.
| prennert wrote:
| There is the advantage of extremely high resolution and crisp
| contrast. The digits can be printed in any colour and on (kind
| of) any texture you like. It scales also very well to very
| large displays.
| numpad0 wrote:
| They offer high resolution full color semi-dynamic display
| without needing any semiconductor circuitries.
|
| You can simply fabricate the flap by cutting the flap to
| dimensions and affixing letterings onto them. That's not
| possible with LCDs or LED arrays.
| michaelt wrote:
| The traditional uses of split-flap displays were sports arena
| scoreboards, airports and train stations.
|
| i.e. places where you want a very large display that's readable
| in direct sunlight.
|
| If you were equipping a train station or airport in the 1980s,
| your options were split-flap displays, CRTs with sunshades over
| them (maximum size ~20 inches), a multi-CRT video wall
| ($$$$$$$$), a vane display (numbers only) or a flip-dot
| display. And a lot of places that were equipped with them in
| the 1980s still had them in the late 1990s.
|
| These days you'd use an LED display, or a sunlight-readable
| TFT.
| mastax wrote:
| I had never realized that the original Sony Jumbotrons were
| CRT (one CRT per pixel) https://youtu.be/AclwH64eAkU
| vidarh wrote:
| When I was a kid our hifi-system had a split-flap clock built
| in (around 1980 or so)
| tyingq wrote:
| Worth noting not all LED displays are sunlight readable.
| Typically, outdoor requires old fashioned through-hole,
| separate LEDS, and at least 1/4 duty pwm refresh.
| dspillett wrote:
| _> And a lot of places that were equipped with them in the
| 1980s still had them in the late 1990s_
|
| Many UK rail stations had them into the early to mid 00s. If
| I'm not misremembering, the boards at London Kings Cross were
| not moved to different tech until at least 2005. Manchester
| Piccadilly had them replaced around 2001 (at the time I was
| passing through there a fair bit, travelling between York &
| North Wales).
| gattilorenz wrote:
| similarly to an e-ink display, it doesn't take energy to show
| the current/last status, it's required only for transitions. If
| there's a blackout, the display is still visible.
| goodpoint wrote:
| > If there's a blackout, the display is still visible
|
| And dangerously out of date in airports and train stations.
|
| When they break down they had to be covered to prevent
| misleading passengers.
| [deleted]
| wayoutthere wrote:
| As someone who used to travel a lot by rail in the not so
| distant past, every station that replaced one of these boards
| was a downgrade. Most stations had maybe 1 or 2 of these signs
| with the rest of the smaller ones already LCDs, so it's not
| like there weren't already places to get the info you couldn't
| show on a sign like this.
|
| Part of the problem with the LCD signs is they show _too much_
| information. It's not really an advantage to show the next 30
| trains incoming on the big board when only the closest 2 or 3
| have gates assigned. They also tend to be themed in colors that
| are harder to read (Amtrak does blue on white, which is harder
| to read than white on black). Some stations tried replacing the
| split flaps with single-character LCD displays to mimic, but
| they always ended up breaking faster (and never getting fixed)
| for some reason.
|
| From what I recall in an article about these signs, industrial
| versions were ungodly expensive to begin with, but the real
| reason they're being replaced is that the companies that
| originally made them are all out of business and you simply
| can't get parts for them. It's cheaper to replace an entire LCD
| panel than it is to fix one of the mechanical signs once and
| you don't have to wait 6 weeks with a broken sign for parts to
| be manufactured.
| theodric wrote:
| Zero power needed to retain image, not encumbered by e-ink
| patent and manufacturing monopoly, simple and repairable, and
| you can build it yourself at home
| goodpoint wrote:
| - Visibility angle is much better than any other alternative.
| This is crucial when one big display is used in a very large
| room instead of many small displays.
|
| - Image sharpness and contrast is excellent. You can read text
| on an old flip display far away that you would struggle to read
| on a modern LCD if you have mild astigmatism.
|
| - Perfectly readable on a sunny day.
|
| - They can show colored logos and symbols (e.g. train type,
| airline, highlight warnings)
|
| - Better failure mode than LCD: single digits fail
| independently from each other and can be replaced. But it's
| less likely that the entire display fails.
|
| - They are either working or stuck - no fading out like CRTs.
| protomyth wrote:
| - oddly pleasant sound indicates change in data
| mschuster91 wrote:
| - they don't require energy to maintain their state - a
| property which they share with eInk displays, but a split-flap
| display is unrestricted in size.
|
| - assuming a fixed output selection, a split-flap display can
| also achieve far greater visual quality than other competitors
| like flip-dot displays
|
| - defective units can be automatically detected (by comparing
| the position of the indicator magnet), whereas stuck pixels in
| flip-dot, matrix or LC displays require a human to spot them
| CyanDeparture wrote:
| To me it's as simple as they look really cool and satisfying.
| danohuiginn wrote:
| Nostalgia, really -- I have fond associations of these with
| childhood train journeys.
|
| I could just about imagine a genuine use case in some kind of
| hostile environment. You could probably make one of these very
| resistant to water/temperature/radiation, with the controller
| kept safely out of the way.
| mjhagen wrote:
| I used to have one of these, but left it above the radiator.
| All flaps warped beyond repair :( So if you're going for
| resistance to harsh environments you'd have to source a
| better material for the flaps, at least.
| grishka wrote:
| Hm, after watching and listening to videos of these
| displays at airports and train stations (don't think I've
| ever seen one in person), I thought the flaps in the
| commercial ones were made of thin sheet metal because the
| flipping sound was somewhat sharper than the OP version.
| argvargc wrote:
| That sparked an interesting idea: would these work in a zero-
| gravity situation (mechanically I mean), and if not, how to
| adapt them so they would?
|
| (And agree with the nostalgia - I'm sure for many the sound
| is associated with a quiet anticipation or excitement of
| embarking on a journey.)
| martin_a wrote:
| They probably won't.
|
| After a flap has passed the upper lip, which is kind of
| holding it back to have a precise "flipping point", gravity
| will take care of moving it down.
|
| No gravity, no flap. ;-)
| amelius wrote:
| You could use suction or flow of air to overcome this. Or
| perhaps even a spring.
| ridaj wrote:
| I think they'll work... Somewhat? As the card is pushed
| through the face, there's a small amount of spring energy
| that it stores by bending, which gets released when it
| makes it through the opening and propels it forward +
| downwards. Normal gravity just adds to that motion and
| keeps the flap moving down. Zero g doesn't help as much but
| the card should already have momentum out of the gate. In
| zero g the problem may be more dealing with the rebound as
| the flap hits the bottom of the frame - it may bounce back
| up and float. May need some dampening or magnetic trick to
| keep it down...
|
| In any case they probably won't work upside down.
| grishka wrote:
| > how to adapt them so they would?
|
| Add rotary springs (is this a valid term?) to the flap
| hinges so they're forced down once released from the top
| edge of the frame.
| fossuser wrote:
| I've always loved these - this company makes one that looks
| great, but isn't open source (there is an API that has yet to be
| released): https://www.vestaboard.com
|
| It's also quite expensive, but has a clever design where the
| individual split-flap modules can be replaced.
|
| There are also custom ones you can have made (probably even more
| expensive), but they're mostly targeting enterprise:
| https://www.oatfoundry.com/split-flap/
|
| It'd be neat to have one you could hook up to some market API to
| make a little stock ticker.
|
| Very cool to see work an open source design.
| chrisdalke wrote:
| This is great! Love seeing hardware hacks like this on HN :)
|
| Beyond just being a cool project, the detail in the README on
| Github is really amazing and I've bookmarked this as a great
| reference for releasing open-source hardware as a git repository.
| CAD files, a bill of materials, detailed usage instructions, etc.
| Animats wrote:
| Moving parts made of acrylic, though. Will not wear well.
|
| Delrin, maybe?
|
| It's now possible to buy commercial split-flap displays from
| China. $180/char.[1]
|
| [1] https://splitflap.en.alibaba.com/
| jiveturkey wrote:
| eh? It's DIY. Make them out of whatever you like.
| Animats wrote:
| They're intended to be laser-cut, which limits the materials.
|
| Those flaps and wheels really want to be injection-moulded
| from ABS, with round pins at the flap ends. That would be
| cheap if you were making enough of them.
|
| (I miss TechShop. They even had an injection molding machine
| good enough to do this.)
| michaelt wrote:
| For some applications you wouldn't worry too much.
|
| A score display for a sports team might only do one or two
| rotations per week.
|
| Of course, for a clock or airport flight display, it'd be a
| different matter!
| oxplot wrote:
| These screens are awesome. I did a design a few years ago, aiming
| for super low cost and easy build. Made a few units but it needs
| more refinement: https://splapr.com/
| amelius wrote:
| I'd buy a watch with this type of display.
| dole wrote:
| How about an NFT watch with a split-flap that displays crypto?
|
| https://robbreport.com/style/watch-collector/jacob-and-co-nf...
| gibolt wrote:
| Related video on Flip Clocks from Technology Connections:
| https://youtu.be/ZArBfxaPzD8
| s0rce wrote:
| After watching this video I feel like every website is showing
| me flip flap displays.
| teh_klev wrote:
| I watched that last night. Alec's a tremendous educator and
| come a long way since his early videos (which are also still
| good). I really enjoyed his deep dive into how dishwashers work
| :)
| smnscu wrote:
| I really enjoy Alec's videos and quirky humour. Beware though,
| this kind of channel is a massive, addicting time sink. Other
| similar channels that HN might appreciate (the first two are
| quite well-known, the last one I found recently and is
| definitely bingeworthy):
|
| - Smarter Every Day
| https://www.youtube.com/channel/UC6107grRI4m0o2-emgoDnAA
|
| - Tom Scott https://www.youtube.com/user/enyay
|
| - Practical Engineering
| https://www.youtube.com/user/gradyhillhouse
| TonyTrapp wrote:
| > Beware though, this kind of channel is a massive, addicting
| time sink
|
| Luckily he only posts new videos every few weeks. ;) And
| almost every one of them is time well spent.
| jedimastert wrote:
| Stuff like this is why I have difficulty giving up YouTube.
| I've given up basically every other algorithmic feed (except
| for HN, I suppose) but the amount of passionate and engaging
| education and curiosity content on YT will have me hooked for
| a while I suppose...
| jamestenglish wrote:
| Subscribed to all 3 of those, one of my new fav's
|
| Stuff Made Here:
| https://www.youtube.com/channel/UCj1VqrHhDte54oLgPG4xpuQ
| Benlights wrote:
| I've found that watching Alec's videos at 1.25X speed made
| them more enjoyable and listenable.
| ziml77 wrote:
| Tech Ingredients is another good one with nice, long videos:
| https://www.youtube.com/user/TechIngredients
| mastax wrote:
| - Marco Reps - Electronics, Metrology, Machining, etc. With a
| dry German sense of humor. Like electric This Old Tony
| https://youtube.com/c/MarcoReps
| iCarrot wrote:
| Also check Ben Eater's for computer stuff
| https://www.youtube.com/c/BenEater/videos
| Gary21857 wrote:
| I must say you have written a great article. The way you have
| described everything is phenomenal.
|
| https://www.mygiftcardsite.one/
| greenyoda wrote:
| Spam link.
| aliswe wrote:
| Id like to make these in arabic ... Would deffo be a big
| challenge with all the shapes though.
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(page generated 2021-04-19 23:02 UTC)