Waterproofing

Before you decide to waterproof something, make sure that it really needs to be waterproofed. It was sure a surprised me, but most DC motors will run just fine completely flooded with water, even salt water.  All sorts of DC electronics will work without any protection, including solenoids, linier actuators, reed switches, and toggle switches.  Now if you can protect these things from water then they will certainly last longer, but it good to know that water does fine its way end the it is not going necessarily cause an immediate failure.

(1) Epoxy, talc, RTV, modeling clay, mixing cups and zip lock bags also for mixing.

Waterproofing Electronics

(1) There are three ways I waterproof electronics and all involve encasing the electronics in waterproof coating of epoxy, RTV Silicone or wax.  The process is called potting.  You can buy real potting compound for around $50 a pint., but common stuff works great and it is much cheaper and easier to find.

Epoxy Potting

Many of the components on circuit boards will not survive even moderate pressure changes.  Harbor Branch Oceanographic actually did test on components in the hopes of avoiding the need for pressure resistant housings or entombing a board in epoxy.  Epoxy comes in two parts and it starts hardening once they are mixed.

(2) I have pumps on the containers so mixing up a small batch is as easy as 1 pump from the catalyst jug for every 2 pumps from the larger resin jug. That goes into a zip lock bag and is squishing it around until it is mixed and then it is poured out.

(2) Epoxy kit with pumps from www.jgreer.com    (3) 5 minute epoxy for small jobs (4) Potting a circuit board   (5) The display is protected with a 1/4 inch piece of acrylic. (6) First coat of epoxy and talc is allowed to dry in order to prevent damage from shrinkage.               Completed Photo   (7) Potting is completed and the plastic mold is removed. (8) Modeling clay used to make a mold for epoxy around wire terminals on a relay. (9) A 100 amp solenoid relay potted in epoxy.  A plastic bag and clay were used make molds for the epoxy.

I often use modeling clay to make a temporary mold around the part I want to encase. A 1 1/2 gallon kit of epoxy and pumps cost about $80 from www.jgreer.com  (3) For smaller parts I also keep on hand some 5 minute epoxy.

(4) (5) To water and pressure proof my "Watt's Up" amp hour meter I cut a piece of 1/4 inch thick acrylic for the face plate, and glued it to the frame of the LCD display with RTV Sealant from the auto parts store.  RTV is also used to temporarily hold more acrylic pieces in place that form a mold.  Once the RTV is dry the mold is filled with epoxy and allowed to set. I made a clay dike around the negative wires used to measure the amps and the shunt they are soldered to. 

You can also add  talc to epoxy in order to stiffen the mix of even make the mix as thick as a paste. Adding talc also stretches your epoxy and saves you money. Wood flower, aka: fine saw dust also works as well as talc.  If your belt sander has a collection bag then you already have a ready source for wood flower.

(6) When potting larger parts like the speed controllers for the trolling motors, it is a good idea to add talc or wood flower because it will also reduce the amount of shrinkage as the epoxy hardens because too much shrinkage might crush a component.  If the epoxy will be more that 3/4 inch thick then it is also a good idea to completely cover the part with a first layer and allow that to harden.  (7) Then the mold can be completely filled with a second batch.

(8) Plastic bags and clay from the craft store are easy ways to make a quick mold around a part that you want to pot.  To pot a 100 amp solenoid relay I first sealed any small holes with RTV gasket sealer, then I put the solenoid end down in a zip lock bag and warped it with tape to keep it somewhat conformed to the shape of the solenoid.  I filed the bag with epoxy and set it aside to dry. Once dry the tape and plastic bag peal off.  It's easiest to do this when the epoxy is still soft because you can use a box knife to trim off the bulges that are not needed and make it look a little less like Frankenstein.  The next step was to roll out some clay and make a mold around the wire terminals on one side and then fill that with a second batch of epoxy. (8) Finally as show in the photo a clay mold was fashioned for the other side of the terminals and that was filled. (9) The completed part is ugly, but it is very waterproof.

(1) RTV Silicon.  Mixed from 2 solutions, it dries in hours and remains flexible.   (2) RTV Silicone gasket sealer is available an auto part stores. (4) Blue RTV gasket sealer used to seal around the wires before 2 part RTV was poured into place. (5) RTV seals the helm control box from water and provides a strain relief for the wires.

RTV Silicone Sealant

(1) If pressure is not and issue then RTV Silicon is a good choice. It dries in hours is a great shock absorber and stain relief for wiring. And unlike epoxy, it can also be easily cut away if a change or repair is needed.  You can buy RTV silicone from www.jgreer.com for about $60 for 1/2 gallon. It comes in two parts, that are mixed together like epoxy.

(2) For small jobs you can also buy RTV silicone gasket sealer in a tube from the auto parts stores for about $5.  

(4) (5) I used RTV to seal the wires going into the helm control box.  This box will be exposed to water but not routinely submerged. wires entering the box were first sealed with RTV Silicon gasket sealer just to plug the hole so that the two-part RTV would not leak out.  The RTV in a tube is more like tooth paste and the two part RTV is like pancake syrup.

I used a piece of duct tape to close up the side and make a mold that could contain the two part RTV which if very fluid when first mixed.  With the mold filled it was just left to dry overnight.

Machineable Wax

Sometimes epoxy is no good because you want to be able to replace a part and RTV is no good because the pressure it high or the part is so large that you don't want to spend that much money.  That is when candle wax is a good choice. The only real problem with wax is that a hot day can turn it turn it back to a liquid.

(1) Machineable wax (2) DIY machineable wax is 1 part polyethylene to 4 parts wax. (3) The mixture will be dangerously hot in order to melt the plastic so wear gloves. Do not follow my example. :) (4) Winch power relay box.   (5) Filled with molten machineable wax.   (6) Having machineable wax around is also nice for its intended purpose for making prototype parts.

 (1) However machineable wax that is designed for prototype work with a mill or lathe softens around 230 degrees and it is much harder the regular candle wax.  You can get machineable wax from www.machinablewax.com or www.freemansupply.com.  A 2 in. x 6 in. x 18 piece is about $50.

(2) I you want to save some money, you can make your own machineable wax by melting polyethylene plastic into candle wax. Since cheep is my middle name I came home from Home Depot with a role of plastic and chunk of wax from Hobby Lobby.  I also pilfered some of Kay's candles that were almost at the end of their life.  

I am certain it will depend on the actual type of polyethylene plastic you use, but a mixture of 1 part plastic to 4 parts wax and by weight was enough to raise the melting point to 170 degrees, an 80 degree increase.  It also makes the wax much harder.. 

Do be careful. If you think hot wax is painful, just wait until you get some molten plastic on you. Also candle wax becomes very flammable when it is hot enough to melt the polyethylene plastic, so do this outdoors with a lid to cover the pot when it burst into flames. 

(4) I used my first batch of machineable wax to waterproof a box that contains power relays which control the winch.  (5) A little duct tape was used to seal around the power cables and then the box was filled with molten machineable wax.

If needed the mixture can be removed by patiently melting it with a torch.  It takes about 3 hours to remove 3 pints.  I know this because I failed to sufficiently tighten the ground wire screw and before I poured the wax into the box.  And the wax managed to isolated the wire and stop it the wench from working! 

(6) You can also use machineable wax for it's intended purpose which is making prototype parts or in my case making a model of a part the will be cast in aluminum.