On Fri, Jun 15, 2018 at 11:46 PM Bill Dube via EV <[email protected]> wrote:
> One of the mistakes folks make it to attempt to make the box completely > sealed. You really can't seal a box effectively without going to extreme > measures. It gets expensive to do this. Because of changes in > temperature and atmospheric pressure, air will find some way to come it > and out, dragging humidity and perhaps water with it. It is, as you say, > best to accept the fact that a box will breathe and to deal effectively > with that breathing. > <snip> All true, which was an even bigger issue decades ago when I was packaging aircraft electronics. Throw big pressure changes due to altitude into the mix and a difficult problem gets much worse. But then a simple and effective solution became available and the whole issue disappeared. Gore, Donaldson and probably others make vent membranes from expanded Teflon (Goretex) that allow water vapor to pass but not liquid water. Donaldson has a version that does the same for oils. These vents are packaged in a variety of forms and sizes, including bare membrane dots with an adhesive ring. They're not widely available in onsey-twosy quantities, but they're out there. So just build your box, make it water-tight (not too big a deal), drill a hole somewhere and cover it with a vent membrane. You just solved the breathing problem, while keeping your electronical innards moisture-free. Temperature changes can still cause internal vapor to condense, but if there's even a little temp rise inside the box that generally goes away. Conformal coating is still a good idea. With that and an enclosure vent, reliability of out-in-the-wind electronic equipment is vastly improved. Chris -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.evdl.org/private.cgi/ev-evdl.org/attachments/20180616/8e1431fa/attachment.html> _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub http://lists.evdl.org/listinfo.cgi/ev-evdl.org Please discuss EV drag racing at NEDRA (http://groups.yahoo.com/group/NEDRA)
