Until today I had only discovered two manufacturers of the split-flap displays of days passed, Solari and Krone. Today I have another, Omega, the departure boards and track signage for Grand Central station has recently been overhalled by a restoration firm called Olek Lejbzon & Co. this firm replaced the old split-flap displays with new LCD units while refurbishing the existing (listed) housings.
The firm have been gracious enough to send me a bunch of photos of these split-flaps and I am in the process of negotiating the purchase of one or two of the units. They are very old by the looks, the design is much more rudimentary than the Krone split-flap displays featured in my post about Jave.de’s project.
So for the past couple week’s I have been working on building up the circuitry, previously I designed, ordered and built up the RS485 board as shown on the right.
The board worked first time thanks to my careful testing and after some debugging of my own stupid mistake which I made not once but twice it worked like a charm.
To test it I hooked up three Arduino’s in a daisy chain with the three identical RS485 boards in Receive mode, and hooked up a USB to RS485 adaptor I bought on eBay, the code was simple, if it gets a 0x00 byte it turns off a LED, if it gets 0x01 it turns on the LED, and surprisingly it worked!
You can see in this diagram how the process worked, and the above image shows the CAT5 cable passthrough connection which means the devices daisy chain easily.
The interesting part of RS-485 is that it uses differential signalling, put basically as you can see on the right the two signals are opposites of each other, which means that the signal is more resilient to noise as the idea is that the two cables are twisted pair (like CAT5) and so they both experience the same noise but are polar opposite signals so the binary output can be determined by looking at the difference between both, this eradicates noise issues.
The board I have been working on this week and a bit of last is the standalone Arduino circuitry. As I am not a micro controller or electronics guru, I want to stick with what I know which is Arduino, however these boards are quite expensive and offer more than I need. My intention is to build a basic Arduino into the circuitry of my project. To do this I needed to do a lot of research and understand what parts are essential.
I have designed and tested on a breadboard the schematic for a basic Arduino and today sent it to be manufactured like the last, I hope it works as well as the last PCB I made so I don’t have to wait another two weeks to get it back, however the idea of making multiple smaller boards that are modular is I will combine them together in one design at the end to make one unit which means it should just work rather than having to mix multiple parts together that might make it harder to debug.
Today I got two sample packs, one from VitasheetGroup which had the wrong stuff in, it was two sheets of the stuff I bought from Pullengers Epsom, and two sheets of white 0.5mm PP with the G01 finish, it’s great because I have something to check the finish is right against, however it’s no good from the perspective of thickness, additionally I can’t really order it because no one sells small quantities anyway.
The other sample was from Saffron Plastics but turned out to be a plain finish i.e. no finish, which was no good and it was 1mm which just seems a bit too thick.
Stephen Webster didn’t answer my email so I called them and a nice chap gave me some quotes for what I want which is ViPrint G01 Black 0.8mm, MOQ was 1775 sheets at 880x440mm, the price per sheet was 84p which is adds up to £1,491 + VAT & Shipping, this would be about a 500 KG of material!
On the plus side he did say they have 950 sheets of ViPrint White G01 0.8mm in stock at 1100x650mm for £1 per sheet which means I can get the right material in the wrong colour and go with that. He also sent a price guide for their stocked material which is all in the infamously crap G02 finish, page from the price list is here: Price List.
I’ve emailed them to see if there is a possibility of piggy backing on another customer who does make large enough order, and about getting 5 sheets of the white as it’s a good price even if it is the wrong colour.
Now that I am not at the Royal College of Art anymore, at least until the new academic year, and with a light schedule of work until graduation next year. I am getting geared up a bit better, my house mate and his girlfriend encouraged me to bring my main computer into the living room where he has his desk, we’ve created a floatilla of jubilee proportions in desk formation.
Luke’s desk, behind mine is a long piece of discovered kitchen work surface stretched across two builders benches. My desk as shown below docks into his desk but has a bit of a raised edge that leans on his. At the left of frame is the kitchen table and that completes the flotilla. This enables me to work in an office situation away from my bedroom which is all the rage in the so-called ‘real world’ and apparently better for sleeping patterns.
With the space left over I have reinstalled my original (came with the house) desk which is basically two battens across the wall, another spare piece of kitchen work surface and a corner support post. This is strangely too high to sit at but too low to stand at, must be an Olympic standard kitchen surface? Anyway I have reinstated it to make a space for my electronic’s and projects area. I will need to get a piece of wood to protect the surface when soldering but otherwise I think it will be a good solution for the foreseeable future.
Note the letter ‘T’ peeking over, this is the V2 prototype that I have yet to photograph, sitting on top of the larger V3 prototype (hidden by my fancy new, second-hand Phillips analog scope).
I called Vitasheet Group again and spoke to one of the staff there, she has gotten me an email address for the UK distribution manager and someone who can provide samples for checking which finish of 0.8mm black polypropylene I would like, the UK distribution manager is the previously mentioned Jed Brooks (firstname.lastname@example.org) and the sample person is Stephanie Penin (email@example.com).
The person I spoke to on the phone suggested a few possible suppliers although she admitted she wasn’t involved with the PP side of things any more, all are new to my search so I will be investigating.
I will be getting in touch with these companies to see what they offer, hopefully I can get some of the G01 (smooth/smooth) finish rather than the G02 (smooth/textured) finish I have been able to find thus far.
One of the issues I have been facing is that the laser cut flaps cut quite well but the black finish is damaged by the high temprature gases that are formed under the cut material.
When the laser point hits the polypropylene it rapidly heats and vaporises the plastic, creating hot gas which pools under the material in the honey comb grill. This leaves a white smokey debris that can be cleaned off but also leaves heat damage.
For many materials this isn’t really a problem because the melting temperature is higher and many materials come with protective plastic stops scratching but also offers protection against this gas. Polypropylene however doesn’t come with this protection as 0.8mm thicknesses, additionally polypropylene has a particularly low melting temperature of only 150ºC which means at anything over 100ºC it can easily begin to effect the finish of the plastic.
The solution to this is to use die cutting, which would have been the method of choice for Solari, Kone and other manufacturers as it allows hundreds of flaps to be produced per minute and the cost of tooling a cutting die reduced the more you use it, while the laser cutter costs remain constant.
With this in mind I asked around some graphic designer friends who they used for die cutting and one came back and suggested Medway Cutters I asked them for a quote for a die cutter for personal use with my design as well as some small runs having them do the work, prices include VAT, exclude postage:
The flap design is probably going to remain the same now so here is the pattern:
The following is a shopping list of items that I am currently planning to use for the split-flap control module controller PCB, it will be responsible for controlling the stepper, sensing it’s current position and receiving commands.
It’s a funny thing that everytime I blog I get one or two people emailing for help, is it that blogging makes Google rate me higher and there are just vast swathes of people looking for someone making these split-flaps or simply coincidence, perhaps I am a fashion leader (who am I kidding?).
Anyways two companies are expressing interest in my work, neither sound like paid jobs but I guess if their experties can help me make my project a reality that would be cool…
I won’t name them this time but one is an another agency who want a reception centre piece, the other is an agency wanting to use it for an exciting client project. The latter project sounds more like it’s going somewhere as they have an actual budget for it and sound like they have experience making other cool projects too!
I am hopeful that my work might finally lead somewhere. What I often wonder is how I am going to make money in this field of work, I would love to do projects like this full time but with the benefit of an electronics engineer to speed up the projects.
If you wish to employ me please email me and that would be awesome.
I am not one for analog printing processes or indeed digital ones, come to think of it I am not one for print processes at all. But making this split-flap display requires a good chunk of knowledge in this area, as the flaps need to be printed onto and the traditional process has been to use screen printing with oil-based inks.
I am very luck to be in a position where I can easily do screen printing with professional facilities, free of charge, however they don’t really allow the use of oil based inks, which are apparently a dying art, primarily because of genuine health and safety concerns in the fumes associated with them and their related cleaning, thinning and retarding chemicals. Oil based inks work best because they are hard wearing and permeate into plastic like polypropylene better.
Trip to the printers!
On Tuesday I went to use the above facilities to do some tests with the kind help of a colleague who runs the facilities called Liz Wilson. She mixed up a bunch of potion inks using her screen printing mojo, and our first ink was to the following recipe:
This potion worked very poorly unfortunately, it was too think and so stuck to the screen leaving a horrible mess as you can see on the right. Also you will note it scratches very easily and is not opaque enough to look really white.
Undisparaged we pressed on and then added 3 tbsp of binder to the mix, and then mixed it in with what was on the screen creating a probably about a 1.5 tbsp mix of binder. The results were again not great, but certainly looked better. At this stage we went for a new idea, we decided to use normal inks but try heat curing them, this is tricky as the melting point of PP is only 150ºC and the ideal curing temperature was some 280ºC!
The first mix was a 50/50 between System 3 white acrylic ink and System 3 textile glue/binder stuff. This was much more opaque and seemed to be better instantly, we tried a high temprature cure without putting the heat press onto the plastic and nothing much happened, instead we dropped the temprature to a boiling 100ºC and used silicone release paper to stop it sticking, the results were good and the flaps were quite resistant to scratching too. I did a few test strips on real flaps to see if the heat press would smoosh the flaps out and cause them to become bigger, this didn’t happen however to get the scratch resistant finish desired I had to put it in for more than 90 seconds and they began to warp:
The final result of the tests with Liz were that I wasn’t happy with water based screen printing and the oil seems off the books for now, I had spoken to a chap called Chris Ratcliffe who advised using Apollo Inks or Screen Colours but it is all getting confusing and I think I need more help from Liz and others than I can really ask of them right now.
I am going back to my old system for now which is using vinyl stickers cut using a craft robo cnc cutter. The next thing is to get the beast back up and running as it’s been abused by students for 2 years and needs new blades and more no doubt!
UPDATE: Just remember that Liz suggested using Fujifilm Sericol Polydyne YD inks which I would have to buy, again like the others I don’t feel confident using them right now so I will hold off on screen printing as it’s just one more problem on the list of things in this project.