Experience with buttons inside potting material ? - Page 1
Forum section: electronics / projects

author: babysitter
author_rank: Frequent Contributor
timestamp: February 13, 2014, 09:06:27 am
content: Hi,I am thinking about a circuit which shall be completely potted in polyurethane, including a battery, intended for single shot use.To prevent the need to mix the potting material again every time and lose time before using, I plan to use a soft power switch cast in.Does anyone have experience with tactile switches cast in a soft potting material? I am thinking about Omron B3F which look somewhat tight to me, hopefully the PU doesn't enter into the inner room which might be prevented by the sealing mass sold for the material right on the switch . To prevent actuation by the (hopefully low) shrinking force, I would buy a high force type.As potting material I am going for a soft 2-component polyurethane,http://www.peters.de/en/products/casting-compounds/casting-compounds-opaque/254-wepuran-casting-compounds-on-polyurethane-resin-basis-pur/519-vu-4444-31-sb-wb-and-vu-4494-31-sb-wbMy trainee is already putting a few buttons on perfboard which we will pot with a slant angle so the height above the plunger is different, but it will take some time until we get the PU maaterial.Thanks in advanceBabysitter

author: enz
author_rank: Regular Contributor
timestamp: February 13, 2014, 10:09:31 am
content: Another idea:How about a reed switch? Can easily be activated by a magnet after potting.I used this a couple of times in hermetically sealed products. Workes well, if it fits your application.Martin

author: babysitter
author_rank: Frequent Contributor
timestamp: February 13, 2014, 10:21:49 am
content: I considered this also, even packing it all up with a magnet for those who use it.Now I am looking into "snap dishes" which might be sealed from the PU when I fix them to the PCB with some adhesive tape, and also rubber switches.

author: babysitter
author_rank: Frequent Contributor
timestamp: February 13, 2014, 11:04:23 am
content: Problem No. 1, drowning and isolating the contacts, should be took care of: one can buy waterproof tactile switches !

author: colotron
author_rank: Contributor
timestamp: February 13, 2014, 11:19:59 am
content: Quote from: babysitter on February 13, 2014, 11:04:23 amHow does it work?. I saw tact switches >IP65 in Digi-Key:http://www.digikey.com/product-search/en?pv69=3&pv69=951&pv69=352&pv697=7&pv697=11&pv697=10&FV=fff40011%2Cfff8005e&mnonly=0&newproducts=0&ColumnSort=0&page=1&stock=1&quantity=1&ptm=0&fid=0&pageSize=100But I initially thought it means that the switches can be assembled automatically because can be washed in the SMT assembly line after soldering.Does it mean also that can be used safely in outdoor environments exposed to water and moisture?

author: babysitter
author_rank: Frequent Contributor
timestamp: February 13, 2014, 11:24:14 am
content: Those that have a IP rating (see quite at the end of the filter lists, searchable attribute) should be!

author: lgbeno
author_rank: Frequent Contributor
timestamp: February 13, 2014, 01:11:03 pm
content: Reed switch sounds like the best idea that I've read on here. It is just fur testing, why experiment with all of this switch stuff

author: calexanian
author_rank: Super Contributor
timestamp: February 14, 2014, 06:03:38 am
content: I would use a membrane switch with an integral ribbon connector going down into the epoxy.