underwater detector tips in construction

[bklein]

I'd like to make an underwater detector based on the surfmaster discussions here. Please advise as to some of the basics involved in making such an underwater unit -
1. what to use for the enclosure
2. what type of potentiometers are used
3. how do underwater headphones or speakers work?

I don't have a physical sample of a surfmaster to go by. I will only be going as deep as snorkeling equipment will allow....

[ApBerg]

Hello
If you go not to deep then the pressure is not a big problem, but to make things real waterproof is not really easy. Keep the most adjustments on the pcb, so you do not need to make to many passing’s in you UW housing. Best … only for the coil and headphone cable .
In the past I used led’s, but they can only be used if there is no bright day light. Audio sound works best.
Use a reed contact for switching the detector on/off.
As speaker use a piezo element that you can make waterproof in a headphone ( hearing protecting ) look at the Fisher UW detector.
What tools you have to make things.. a lathe ?, can you get pressure pvc pipe, 40 mm inside, and solid round pvc for making end caps with o-rings and cable passing’s in it ?
Regards.

Ap

[bklein]

I have a fairly good selection of tools except no lathe or mill.
I have seen an instructables article on making a waterproof enclosure using a plastic box and plexiglass cover with hot melt glue and vinyl repair glue. There are also some boxes available at retail I just haven't found em yet. But what about the controls? Are there pots that have waterproof shafts or are these really more accurately described as water-resistant rather than waterproof and the pots rather standard? Or is it the kind of situation where you can pretty much set everything up before going into the water anyway? I'm not going to be doing a lot of underwater searching, just want to check a boat ramp that I visit a few times a year.
I am also near the beach so it would be nice to have it for that too.

[grungymike]

waterproof

I'm going to be facing a similar challenge when I build my 2nd detector.

Take a look at the Pelican cases, they've got some dandy waterproof stuff with a latching cover that makes getting inside pretty easy (as opposed to screws). They've got a website.

As for pots, I think you want stuff rated IP68 (30m deep). If you go to Wikipedia you can download an excellent explanation of how the IP rating system works. Then it's a matter of going through the catalogs, Mouser and Digikey are both really good. Precision Potentiometers carries pots that are hermetically sealed, again the've got a website.

Also, as for waterproof connectors, check out the Bulgin Buccaneer series, they're rated IP68, multiple conductors and power ratings.

As for switches, Alcoswitch makes full boots that completely cover the switch toggle, effectively waterproofing the switch. I haven't yet found a switch, toggle or rocker, that really meets an IP68 rating without using a boot. Some switches use an internal O-ring on the toggle ball, but I don't think they intended any more than protection from rain.

A final thought, I remember reading in a White's manual (I think it was an early surmaster manual) that they recommend a bag of silica dessicant gel in the control box. It helps protect against minor humidity that will eventually get in there...

gm

[bklein]

wow, great stuff! Great help. Thanks!