enter image description here I want to use a pulse width modulator to replace the on- off switch on my modified electric trolling motors. (I take disabled vets out on motorized kayaks). The modulator works great but, I need to water proof it somehow. What's the best way to do this? What material should I use ? How do I apply it and what should I not apply it to? From my research, I understand some of the issues such as using an epoxy for instance that is thermally but not electrically conductive and that has minimal shrinkage when it dries.

  • \$\begingroup\$ Can you give us some information on the "phase width modulator"? - like if it dissipates any heat, and if is it a part you bought, or made yourself. Have you considered a water-tight enclosure with appropriate cable glands? \$\endgroup\$ Commented Dec 6, 2015 at 19:17
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    \$\begingroup\$ It's a VERY good idea to have a physical on-off switch in series with the electronic one. | Heat and power dissipation need considering but you probably want a substance known as a "conformal coating" that is specified for the sort of environment involved. I could give specific types BUT there are many brands and a quality/reputable manufacturer is often the best choice. Dow Corning is one such (many products) but there are many others. \$\endgroup\$
    – Russell McMahon
    Commented Dec 6, 2015 at 19:20
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    \$\begingroup\$ If heat isn't a big issue, I would personally put it in an IP67 rated enclosure with appropriate cable glands to pass wiring in and out. If you want to be extra paranoid, spray some conformal coating on the PCB for added moisture protection. \$\endgroup\$ Commented Dec 6, 2015 at 19:21
  • \$\begingroup\$ I attached a pic of the pwm to my original post. I have reviewed the different types of coatings. What should not be coated on the board? Thanks for the comments everyone. \$\endgroup\$ Commented Dec 6, 2015 at 20:04
  • \$\begingroup\$ Well the potentiometer is going to be an issue. There are many openings for moisture. Perhaps use hot-melt glue to seal the openings, but the underside of it looks tricky. On second thought, I concur with the IP67+ enclosure. \$\endgroup\$
    – rdtsc
    Commented Dec 7, 2015 at 1:43

1 Answer 1


Consider one of 3M's Novec coatings. Ive used them before they do a good job of protecting the electronics. After all that's what it is designed to do and it does not hurt heat dissipation much. The hardest part will be getting a good enough coating on the potentiometer.

Be sure to research which coating works best for you


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