How to do this kind of button and where to source ? - Page 1
Forum section: electronics / beginners

author: vibram
author_rank: Newbie
timestamp: August 29, 2018, 12:39:26 pm
content: Hi everyone,First post: i did my homework but was note successful at all.I would like to do my own keyboard such as following picturesI think this is a matricial keyboard, isn't it?But I don't find a tutorial to explain how to make it and where to source this kind of flat button.And same thing for the plastic cover, i find nothing about it. Maybe I'm not looking correctly but it doesn't seem to be widely spread in the DIY community.Any help appreciatedThank you

author: Ian.M
author_rank: Super Contributor
timestamp: August 29, 2018, 01:18:25 pm
content: Google:metal tactile click domeThere are plenty of sources including major component distributors. Look for manufacturers' design guides (once you've found a supplier, as they are specific to an individual product) to get implementation details like recommended PCB footprint and finish, surface membrane material and thickness, and separator thickness and hole size.

author: vibram
author_rank: Newbie
timestamp: August 29, 2018, 01:32:58 pm
content: THank you IAn, this is exactly what I needUnfortunately, it doesn't seem to be wide spread for one time project (obviously due to cost and quantity...) but i will think about it

author: mleyden
author_rank: Contributor
timestamp: August 29, 2018, 02:05:40 pm
content: Matrix keypad, membrane keypad...Membrane keypads need tooling and are printed, requiring the manufacture of a number of layers. Getting one will be expensive unless you can buy an existing one and alter your housing? If you don't need the toughness of a membrane keypad, think about a matrix of push switches. If you do need to operate in a harsh environment, think about capacitive keypads:www.ti.com/lit/ug/tiduaz5/tiduaz5.pdf

author: vibram
author_rank: Newbie
timestamp: August 30, 2018, 06:51:02 am
content: Quote from: mleyden on August 29, 2018, 02:05:40 pmTHank youI need to see how I can interact with my STM32 and more important, which surface I can put on

author: Zero999
author_rank: Super Contributor
timestamp: August 30, 2018, 09:34:55 pm
content: Quote from: mleyden on August 29, 2018, 02:05:40 pmCapacitive keypads very robust and have a theoretically infinite life, but moisture, even very sweaty, damp fingers can interfere with their operation. Another downside, compared to mechanical switches is they lack tactile feedback, the feel of the switch being pressed and the click sound which lets the user know they've pushed a button.

author: GeorgeOfTheJungle
author_rank: Super Contributor
timestamp: August 30, 2018, 10:00:54 pm
content: Those are ~ like the hp calculator tactile feedback style keys, the best ever.https://www.keesvandersanden.nl/calculators/patents/US3941953.pdfhttps://www.keesvandersanden.nl/calculators/patents.phphttps://patents.google.com/patent/US3941953

author: Mr. Scram
author_rank: Super Contributor
timestamp: August 30, 2018, 10:11:42 pm
content: I think one of the usual Chinese suspects makes these in prototype quantities for not stupid money. Let me see whether I can dig up which one.

author: Mr. Scram
author_rank: Super Contributor
timestamp: August 30, 2018, 10:34:14 pm
content: Here we go. That page doesn't seem accessible from their current website, so I'm not sure they still do it.https://www.allpcb.com/membrane_switch_quote.html

author: Ian.M
author_rank: Super Contributor
timestamp: August 30, 2018, 11:24:44 pm
content: Quote from: Ian.M on August 29, 2018, 01:18:25 pmQuote from: vibram on August 29, 2018, 01:32:58 pmIf you don't need the top layer with the printed keys to be vacuum formed so each key is actually a raised dome, and are prepared to settle for a flat surface, its entirely DIYable. The click domes themselves can be bought in small quantities: 50 off for a few bucks on AliExpress, or right down to one-off quantities from Mouser and Digikey. The separator layer can be constructed from just about any sort of rubber sheet of the right thickness to match the click dome height once its stuck down, and the holes punched with a home made hardened steel tube punch, sharpened from the inside, with a concentric protruding coil spring inside it to eject the punchings, working on a hard plastic chopping board as an anvil, punching through a paper layout taped to the top of the rubber sheet. The top membrane can be printed for you by just about any sign shop that does self-adhesive exterior printed vinyl signs.I also *think* you could get close to the original domed surface keys if you made a vacuum forming mould, got the vinyl without an adhesive backing and with a clear top layer protecting the print, and after tape sealing the oversize edges to your mould, carefully applied vacuum and heat, but I'd bet you'd ruin quite a few figuring out the process parameters even if you initially did partial sheet test runs to get more attempts per printed vinyl sheet.Once its figured out, punch a double sided adhesive film with its backing papers still on, make a jig with magnets under the PCB to hold each dome in place, and apply the punched adhesive film and the formed vinyl, then press with a matching punched rubber sheet (reusable) on top to avoid pressure on the domes to get good adhesion.It would probably be somewhere around $50 in materials and printing (+ a lot of labour) to DIY a flat surface reproduction of the keypad you showed above as a one-off, and a lot cheaper per unit (again ignoring labour) in 10 off quantities. Above that, talk to a custom keypad manufacturer or set up a sweatshop!