Advice sought on snorkelling housing.

[Goaty]

With my Pickini up and running on the bench I have now started work on the waterproof housing for it.

My intention is to make a detector suitable for shallow water snorkelling, but since I have had no experience with this type of detecting I am seeking advice on what dimensions are the most practical.

This photo shows my housing to date -



At the moment the entire thing is just a press fit with no glueing or seals.

I would like advice on such things as -

best length for shaft (currently 50cm)
best angle for coil to shaft. (this angle will be fixed once completed)

My concern is that if the shaft is too short the electronics may interfere with the coil and if too long it will be difficult to swing under water

The housing is 20cm long 50mm diam pvc water pipe, the shaft is 50cm of 20mm pvc conduit and the coil housing is 16mm pvc conduit.

[Funfinder]

50cm is too long - with such a relative small coil you can use 30cm without significant interference-problems.
This is much better for sweeping and pinpointing while diving (also for scrubbing sand etc aside).

But the other question is how to receive the detection signals - by waterproof headphones or inbuilt vibration.

[Goaty]

Thanks for your input Funfinder.

I'm afraid I have already started the assembly of the housing and it may be difficult to alter, but if the housing is successful (and the Pickini works underwater!) I plan to build a modified Mk2 version.
At the moment my biggest hurdle to overcome is going to be in keeping the sea water separated from the electronics. Fortunately I have enough spare parts on hand to build several more Pickinis.

For a target indicator I plan to use a high brightness white LED inserted through the housing, sealed in and angled back towards the operator so it should be readily visible.
Ultimately I hope to use vibration as well but ,at the moment, am trying to adhere to the KISS principle (Keep It Simple Stupid ).

For retrieving finds I plan to make a short handled PVC sand scoop.

[Funfinder]

Mega stupid simple would be using some transparent small tupper-ware etc. box.
At one side you stick the coil-cable through, attach a short stem for the coil and
make the hole waterproof with epoxy etc.
On the inside the cable still needs to have some inches / cm for changing batteries etc.
After fixing a handle to the bottom of the box your pistol like "harpune" is ready to dive.

[F117]

This is the housing I used for the prototype of Pickini v4 for diving:

http://www.geotech1.com/forums/showt...708#post229708

It is a "tupperware-like" box. There are no external controls.
It needs to be opened before diving to switch it on and set the sensitivity.

In open water, the sensitivity can be cranked up quite a bit.
The first tests were in a 15m deep diving tank. The dive tank is an old metal fuel tank from a power plant : http://www.duiktank.be/

Needless to say that the detector kept beeping all the way down ( and up again ). There is an internal - very loud - piezo beeper inside the housing, that can be heard clearly underwater.

[Goaty]

I've manager to 'shoe-horn' the standard Pickini board and 3 X 18650 Li-ion batteries into the pvc pipe housing.
It was a tight fit getting the board in and I had to cut the excess fg from the sides of the board right back to the copper tracks.
The next task will be to get some o-ring grooves machined into the ends of the pipe to seal the end caps but still have them removable for battery charging and adjustments. I would have preferred threaded end caps but there does not seem to be anything available to suit the pvc pressure pipe.
The wall thickness is 3.3mm and I plan to use o-rings with either 2mm or 2.4mm c/s diam - the grooves will need to be very close tolerance!

@F117
I like your idea of using a loud piezo but wonder if it would be audible through my pvc housing.
Did you test your housing to the full 15m in the dive tank?

[F117]

I like your idea of using a loud piezo but wonder if it would be audible through my pvc housing.
Did you test your housing to the full 15m in the dive tank?

In the plexi housing I used, the piezo buzzer is glued to the top case. Sound is very loud and clearly audible.
This was my quick and dirty solution instead of waterproof headphones and an extra hole in the housing for the headphone cable.
I am in no way a mechanical wizard and I know my limits...

The first tests were with an on/off reed relay that could be activated through the housing by an external magnet.
But because the inrush current is too high, the reed contacts were welded together and the detector could not be switched off

If pressure is a concern, you could consider pouring liquid parrafin / wax into it.
I also did this with a first drain pipe housing and had to melt it down each time I suspected a leak in the tube.

And yes, we tested it all the way to the bottom of the dive tank, much to the surprise / displeasure of other divers ( the buzzer went off all the time ).

[bernte_one]

if you use transparent enclosure use the led Output from Controller

for double security again water leaks put an smaller tupper box into a bigger one

you can hardwire your coil cable direkt from coil through box and connected to pcb

but in other case that you wish to Change Setup use hexseal plug and socket with lockring

good luck