Thanks Bruce for all the tips! Will take it into account.. 2015-07-14 19:26 GMT+02:00 Bruce Boyes <[email protected]>:
> Look into conformal coatings such as Miller Stephenson MS-460H > <http://www.miller-stephenson.com/products/detail.aspx?ItemId=56> or MG > Chemicals. Sealing all the connectors and sockets will be a problem, but > you can get a silicone paste used in sealing connectors such as in > irrigation systems. Check out the 3M Scotchlok connectors > <https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=4&cad=rja&uact=8&ved=0CE0QFjADahUKEwjLx8WkjNvGAhVNoogKHfGRCK4&url=http%3A%2F%2Fsolutions.3m.com%2F3MContentRetrievalAPI%2FBlobServlet%3Flmd%3D1413989307000%26locale%3Dpt_PT%26assetType%3DMMM_Image%26assetId%3D1361822756031%26blobAttribute%3DImageFile&ei=DEClVcuRKc3EogTxo6LwCg&usg=AFQjCNGRv6hQtATKwOJJQKu4-Gx-sFpcTw&sig2=6bALbBmsLoRqH9wSS-57jw> > which we are testing now in fresh- and salt- water aquatic environments. I > like the suggestion of immersing the whole board in some nonconductive, > preferably hydrophobic fluid, maybe something on this list > <http://www.electronics-cooling.com/2006/05/an-overview-of-liquid-coolants-for-electronics-cooling/> > ? > > Lightning may be an issue. There are various ESD protective devices. We > have used them on Ethernet connections and had good survivability of our > (now obsolete) systems used in weather stations where a competitor's > (without such precautions) got taken out repeatedly. So consider where any > wires enter the enclosure, protect them from ESD and surges, and make your > enclosure a Faraday cage. > > We've have systems we designed in field for more than ten years and still > working. Some are used on thruway systems (I'm not sure exactly how), some > are in dairy plants, etc. We got back one system a while ago - it had been > (accidentally filled with milk which over time curdled and rotted and > became conductive and eventually 120V in the system (we voted against > having any mains power in the enclosure but were overruled) arced through > the milk pudding and killed everything. This system had red 7-seg LED > displays which must have been observed to get cloudy as this situation > developed but no one did anything until it died. It was a stinky charred > mess when we opened it up. They asked if it could be repaired... but I > digress. > > Heat is the enemy, any liquid paste electrolyte caps or batteries will > die. You want all solid caps. Redundancy is good. Look at the aging data > for components and don't push their operation to the edge of voltage or > temp and design to the worst limits of aging, temperature, power supply, > etc. > > Over the years I'd say 90% of system failures we see are the power > supplies (usually customer-supplied for one reason or another), so if they > are solid you should be good. We typically design local on-board regulators > and fuses (sometimes sacrificial PC board traces feeding a heavy zener > diode) and have lost very few systems even when power supplies have failed. > Then we feed a group of boards with a higher voltage (12V or 24V more > recently) DC supply which is locally down-converted where used. The raw > supply can fade or misbehave a lot and still not take out the local boards. > > On a good day you get what you pay for, so use good quality components > designed for the task and you'll be happy later when your phone doesn't > ring with in-field problems. > > best regards > Bruce Boyes > -- For more options, visit http://beagleboard.org/discuss --- You received this message because you are subscribed to the Google Groups "BeagleBoard" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/d/optout.
