Ring Terminal Connections for Harsh Environments

[opmal7]

I'm working on a project that uses solenoids for mechanical activation. The solenoids have lugs for the + and - electrical connections. I am connecting my wires to the lugs with ring terminals.

The problem I have is that the product will be subject to outdoor, harsh environmental conditions. I'm looking for a way to connect to the lugs and protect the connections from the environmental conditions. Once the ring terminals are attached, the only reason to disconnect them would be if the solenoid breaks and you have to replace it.

I've thought about just connecting the ring terminals and putting heat shrink wrap around the terminal and lug, but that seems like a "DIY" or hobbiest solution. I was wondering if anybody might have any advice on a more professional looking solution. If anything is unclear, feel free to ask questions.

Thanks in advance.

 

[dlgoff]

The environmental conditions would determine what I would do. Around here, I probably would just leave the lugs to the elements. What are your conditions? What voltage does the solenoids require? Could they fit into an outdoor box?

 

[jim hardy]

I see heatshrink as okay provided it won't trap water...

perhaps a conformal coating

but if you're after that elegant touch, i'd think your solenoids are probably available with leadwires to which you could affix a connector. Look under your automobile hood at the robust connectors on the engine sensors...

old jim

 

[AlephZero]

I would forget about the heatshrink, and just use a good thick layer of grease. That's assuming the components are sheltered from direct rain and snow that would wash the grease off over time.

It could be hard to apply heatshrink properly around something as "lumpy" as a ring terminal connection. If it's not completely sealed, narrow gaps will tend to draw water in by capillary action instead of keeping it out.

 

[the_emi_guy]

Pay close attention to the types of metals and their plating.

Look up "galvanic table" for metals on the Internet. You do not want current flowing across the boundary between dissimilar metals. Lugs and terminals are available in a variety of metals. Definitely do not crimp copper wire into aluminum or steel terminals, or mount a nickel plated l terminal onto a tin plated lug.

Give us some idea how much current you are talking about. A considerable amount of electronics makes use of gold plating on contacts because it resists corrosion naturally. Small gold plated spade lugs are available from Pomona.

The next thing you want is a "gas tight" connection. It is not enough to prevent liquid water from creeping in between contacts, blocking water vapor infiltration is also necessary. Gas tight connections are achieved by using soft metals with high contact pressure so that the metals bite or deform into each other rather than just resting on top of each other. There are special tools used to crimp stranded wire to terminals which enforce the necessary pressures. If you can, you may be better off using solder terminals.

Finally, you will want to coat the whole thing with something that resists moisture. Plain ol Vaseline (petroleum jelly) is a popular way to protect car battery terminals. Or purchase some dielectric grease (as AlephZero suggested).

There are other reliability nuances: you do not want to crimp solid wire, whereas compression or clamping can be used on either solid or stranded.

Hope this isn't more than what you were looking for.