Tact-switch splash-proofing - Page 1
Forum section: electronics / projects

author: colotron
author_rank: Contributor
timestamp: February 12, 2014, 09:46:15 pm
content: I'm working on a project using an enclosure similar to an usb-stick, intended to be water-splash resistant (IP54 or better).I need to include a tactile switch in the pcb, hence I have to make an opening in the enclosure to use the switch. There isn't any other openings in the enclosure.Is there any way to cover the enclosure hole with a flexible membrane/film to block water entry and still being able to push the switch?.I saw this:Also this:http://www.zago.com/products/crystal-switch-seals/tactile-and-dip-switch-seals/but the available space is constrained and can't use seals that big.Have to choose the tactile switch yet, but I need to know how to solve the water proofing first.I have 5mmx5mm on the PCB to use a surface mount-top actuated switch, maybe something like:http://www.digikey.com/product-detail/en/KMR231NG%20LFS/CKN10246CT-ND/2176497http://www.digikey.com/product-detail/en/PTS820%20J20M%20SMTR%20LFS/CKN10505CT-ND/4176679Don't know if using plunger/cap/other accessories is recommendable.Any suggestions?

author: Corporate666
author_rank: Unknown
timestamp: February 12, 2014, 10:35:13 pm
content: I've solved waterproofing problems in various ways with various levels of success.In your case what about a small square of thin (and therefore flexible) silicone or rubber sheet applied to the underside of the housing before assembly - such that when you put it together, the plunger of the switch pushes up into the membrane and can be pressed through it.

author: colotron
author_rank: Contributor
timestamp: February 13, 2014, 12:15:03 am
content: Thanks Corporate666.Yes, I think that can be easy and cheap to do, but I'm not sure about the commercial products available.Maybe something like this?:(Fromhttp://www.rollsheetrubber.com/html_l.aspx?id=789)What adhesive/sealant can I use to glue it to the enclosure (ABS plastic)?: silicone?, some of this?:http://solutions.3m.com/wps/portal/3M/en_US/Adhesives/Tapes/Products/~/Industrial-Adhesives-Tapes/Adhesive-Sealants?N=5510818&rt=r3Maybe some glue used in aeromodeling?

author: NiHaoMike
author_rank: Super Contributor
timestamp: February 13, 2014, 05:03:44 am
content: Rather than cut a hole in the casing, make the casing out of a somewhat flexible material so that applying pressure activates the button. Or if it's plastic or some other nonconductive material, use capacitance sensing instead of a mechanical button.

author: babysitter
author_rank: Frequent Contributor
timestamp: February 13, 2014, 09:24:00 am
content: If it is for a single-shot hobby project, drill a hole about 2x diameter of the plunger, plunger front just below the outer edge, stick a paper label on your device and wrap it in the kind of self-adhesive foil used to protect books.For a commercial device, consider a membrane made of lexan with a "dome" shaped stamped on it made by a electronics fabbing house, or go for a membrane keyboard, or a rubber membrane (in that case I might be able to help you get something interesting...)Edit: People that know might also have a look at my thread herehttps://www.eevblog.com/forum/projects/experience-with-buttons-inside-potting-material/new/#new

author: colotron
author_rank: Contributor
timestamp: February 13, 2014, 10:28:22 am
content: NiHaoMikeAlready buy the enclosure, I'm afraid I can't use another one.Initially thought to implement the button using capacitive-sensing. But then a tact switch seems to be better:the microcontroller doesn't have capacitive sense I/O hardware, and will be necessary to wake-up the micro every second to scan the key; also (and more important) there is the possibility of accidental touch detection by splashing water/unintended touch (just by grabbing the thing).With the tact switch I don't have to wake the micro to read the switch, the switch will wake the micro; and there is no possibility of accidental button activation.The change in mind is not final, depends on how hard is to do the tact-switch stuff.BabySitterIt's not for a single-shot home project, but neither for a thousand units product, lets say a few tens per year. Doesn't have to be consumer-grade nice looking quality neither. A few dodginess is allowedreliability is more important.I will dismantle some membrane keypad laying around and see if I can use the key-membrane.

author: HSPalm
author_rank: Regular Contributor
timestamp: February 13, 2014, 12:42:59 pm
content: Place a small mic inside and you can simply shout your commands at it.

author: lgbeno
author_rank: Frequent Contributor
timestamp: February 13, 2014, 12:57:22 pm
content: Post a link to you enc drawing

author: colotron
author_rank: Contributor
timestamp: February 13, 2014, 01:13:57 pm
content: HSPalm, already considered a mic, but the unintended activation still being a problem.lgbeno, here it ishttp://www.mouser.com/ds/2/290/260906_r4_5-13573.pdfLooking athttps://www.eevblog.com/forum/projects/experience-with-buttons-inside-potting-material/msg386748/Make me consider using some IP67 tact-switch and sealing the switch metal body to the enclosure, leaving the plunger exposed to the outside free to be pushed (didn't know about IP67 switch existence). They are a little bigger than I wanted (5x5mm vs 6x6mm), but I can make a little more roomCandidate switches:http://www.digikey.com/product-search/en?FV=fff40011%2Cfff8005e%2C1140003%2C1140160%2C11403b7%2C4080043%2C4080075%2C8dc0013%2C8dc0019%2C8dc0048%2Cae40007%2Cae4000a%2Cae4000b%2C182c0016%2C182c002a&mnonly=0&newproducts=0&ColumnSort=1000006&page=1&stock=1&pbfree=0&rohs=0&quantity=1&ptm=0&fid=0&pageSize=100]http://www.digikey.com/product-search/en?FV=fff40011%2Cfff8005e%2C1140003%2C1140160%2C11403b7%2C4080043%2C4080075%2C8dc0013%2C8dc0019%2C8dc0048%2Cae40007%2Cae4000a%2Cae4000b%2C182c0016%2C182c002a&mnonly=0&newproducts=0&ColumnSort=1000006&page=1&stock=1&pbfree=0&rohs=0&quantity=1&ptm=0&fid=0&pageSize=100]http://www.digikey.com/product-search/en?FV=fff40011%2Cfff8005e%2C1140003%2C1140160%2C11403b7%2C4080043%2C4080075%2C8dc0013%2C8dc0019%2C8dc0048%2Cae40007%2Cae4000a%2Cae4000b%2C182c0016%2C182c002a&mnonly=0&newproducts=0&ColumnSort=1000006&page=1&stock=1&pbfree=0&rohs=0&quantity=1&ptm=0&fid=0&pageSize=100Edit after reading the other post: damn... reed switches... why I don't think that before....