Underwater detector - build suggestion

[CDI]

Thank you godigit1 and blobber. I will post my result next month, just ordered from China some parts and wait to come.

[Funfinder]

Underwater-Housings for Cameras:
https://www.amazon.com/Underwater-Ph...8&node=3350301

[6666]

Hi CDI
For the switch you can use a magnetic switch or make a diaphram for a rocker switch. The pots can be magnetically controlled, I used levers and roller bearings attached to knobs inside my case. Its not the prettyiest but it is fully functional and adjusts easily. Only thing is you need allot of room inside your case for this. I had to build my battery pack into the shaft. This was my first water proff detector and if I did it again I would use the magnetic switch instead of the diaphram beacuse you then only need two holes in your case for the coil and headphones.
The MPP I did this to is #11 on the MPP finished builds thread.

godigit1
Just watched your video I see you alter the delay and threshold , when you bring the detector out of the water is there any change ?


And when underwater once the controls are set is there any need to alter them ?

[6666]

The coil I have made from epoxy resin, fiberglass and cotton flakes.
First I laminated 2-3 layers fiberglass 165 g/qm on a flat surface, which is protected with PP-foil. The 20 turns of wire comes directly on the layers. With thickened resin with cotton flakes, in a consistence like butter, I filled all gaps, transitions and reinforcements. A piece of rubber ist placed for the rod holder. Than again comes two layers of fibre glass 165g/qm drapable twill fabric (Google translation, I don't know if this is correct). All layers are laminated wet on wet.
When all is dry and hard, you can cut the shape of your coil you want.

*

Thanks for the info.

[CDI]

I will use this pvc pipe for pcb housing...
http://www.forum-pn.rs/images/proizv..._1518_1518.jpg

[godigit1]

Hi 6666
I have only submerged the detector in a tub so far but I have been in and out of the surf with it. I have done several beach hunts with it and Im very happy . As far as the delay and threshold goes my threshold stays stable in and out of the water(using a TDI dual field coil) my delay I have to adjust. I run around 8us on the beach as I hunt for small jewelry I mostly find earrings. When moving to the wet sand and surf I have to adjust my delay to around 12 to 15 us as it gets a little chatty at 8us.
Also if I do have to adjust while in the water it is easily done with a rare earth magnet without opening the box.
I just yesterday received my new water sand scoop picked up my wetsuit from storage and I see a break coming in work soon.
Im back home in tahoe now so Im dying to do a water hunt asap.
I will post my results when I can get out and see if underwater changes anything for me.

[godigit1]

godigit1
Just watched your video I see you alter the delay and threshold , when you bring the detector out of the water is there any change ?


And when underwater once the controls are set is there any need to alter them ?

Hi 6666
Thinking about your post, in my video I dont alter the threshold?? I set my threshold to a tick tick instead of a low growl. its easier on my ears and any frequency change is very easy to hear. The threshold change in my video is the twelve inch nickel I burried. I really am not to good at videos as you can tell. Next time I will mount the camera on the detector or use a tripod.
Take it easy.
Digit

[6666]

Hi 6666
Thinking about your post, in my video I dont alter the threshold?? I set my threshold to a tick tick instead of a low growl. its easier on my ears and any frequency change is very easy to hear. The threshold change in my video is the twelve inch nickel I burried. I really am not to good at videos as you can tell. Next time I will mount the camera on the detector or use a tripod.
Take it easy.
Digit

Hi Godigit, thanks for the reply, I'm interested in how much variation you have with the threshold from when the machine is in sea water and when you take it out, you have a very clever method with the magnets, but once the machine is in the water , and setup do you have to readjust the settings,
a member here TEC has a very simple system for his pots.

He uses just a pvc tube to house the pcb with an end cap, he unscrews the end cap, and with the coil in the water adjusts the delay ,vol and threshold pots etc and screws on the cap and makes it water proof, in recent times I've been thinking that's all that's required to make a water proof machine if no adjustments are required in the water.

[godigit1]

Hi 6666,
I see what you are getting at now. Yes to make a detector water proff all you need is a case that is tight. But I think no matter how stable a machine you have your going to have to adjust on the fly in the water just as well as you do on land.
When I built my MPP I wanted a wader for Lake Tahoe. You would not think a fresh water lake could be that challenging ground wise, but there are beaches that a Vlf will barely operate without overloading. So for me it is more about having the ability to alter the delay for ground conditions.
But if you have consistant sand like some ocean beaches you should be able to get in the water make your adjustments when the electronics stabelize set it and forget it while your in the water.
I originally came up with the little roller bearing thing trying to think of a way to water proff my gold bug pro because I love it for jewelry hunting.
But that never happened at least not yet.

[reptooyep]

Thank you Eric for your information and suggestions.
While I was searching, I found the original files for Garrett XL-500 Pulse with Google. Is that correct?
Anyway, it seems for me the same function. Well, sensitivity with switch. Can you or someone explain the task of
LM358 or the other difference to the version, which I have made?

Fred


[ATTACH]36921[/ATTACH]

Hi Blobber (Fred),
Thanks for sharing your layout.
I'm making a waterproof detector to use it in salt water scubadiving.
I have few questions about the motion pi detector :

1st: Do you think IP67 pots would work in salt water ?
2nd: Can you explain few thing about tuning this unit ? I mean, adjust the trimmers on the board.
3rd: I have two coils waiting for a detector (see picture). Which one do you think is the best for this detector (maybe none ???) ?

I was puzzled the first time i saw the shematic cause the + power is generated by a charge pump on the negative power with NE555 ... It was strange for me, usually, it's the opposite way but waybe i did not see enough schematic ...
Your help would be appreciate.

[blobber]

Hi Blobber (Fred),
Thanks for sharing your layout.
I'm making a waterproof detector to use it in salt water scubadiving.
I have few questions about the motion pi detector :

1st: Do you think IP67 pots would work in salt water ?
2nd: Can you explain few thing about tuning this unit ? I mean, adjust the trimmers on the board.
3rd: I have two coils waiting for a detector (see picture). Which one do you think is the best for this detector (maybe none ???) ?
[ATTACH]37064[/ATTACH]
I was puzzled the first time i saw the shematic cause the + power is generated by a charge pump on the negative power with NE555 ... It was strange for me, usually, it's the opposite way but waybe i did not see enough schematic ...
Your help would be appreciate.

I think, I should answer in this thread here. Where I had posted my layout file.

http://www.geotech1.com/forums/showt...(pulse)-XL-500

[reptooyep]

Hi everyone,
I'm still having troubles making my xl200 working but i'm sure i'll find soon the solution.
I'm comibg back to the forum to share my work on the waterproof detector.
I made a wireless power supply with an broken archos battery, a charging board and a stepup board.
With this configuration, you can seal your box for many years without touching the battery.


The black box contain a home—made colpitts oscillator and a 10 turns 0.5mm coil. It's powered by a 12v, 1.25A block.
The receive board contain 4 diodes, a 7805 regulator, a 1000uf and 100uf caps, a stepup board (4v to 12v) and a tiny
Charging module.
To limit the Ic current, i put 3 4.7ohm 5W resistors and the box get realy hot ... but it works pretty well.
The best thing is to put a 10W 15 or 20ohm resistor.
Hope it can help.
The charging time is long but i don't care about that.

[blobber]

Yes it's looking very interesting. But more complex, as I expected.
I think, a similar system with the induction principle are used in electric toothbrush.
I wonder, could it be, that such devices are also usable for our units? What do you think about that?

I don't know this type of your battery, do you have a link?

[reptooyep]

The battery has been scavage from an archos tablet. This is a 5000mAh 4.1v lithium ion. With the stepup board, it gives about 12v 1500mAh. After 10 hours underwater, i think i'll get cold...
The toothbrush is a good idea but i'm not sure of the voltage. I have to check this ..

The simpliest way is to buy a QI circuit (2.5€ from china) and a QI charger (few € too). But if you use low voltage battery, you MUST use a stepup board (1€ from china).

[blobber]

Well, I was thinking about your power supply, because all 2-3 years I have to change the NiMH battery. The unit I only use in vacation, so the most time, it's waiting...
So today I've ordered some stepup boards, they are realy cheap 5 for 4€. I wonder and can't imagine, that such business, is a profitable business for the sellers. Generally I don't understand, why electronic components from China are almost free.
Anyway, I also ordered a slim powerbank with 5600mAh it's more than enough, but the size fits to my enclosure. I was thinking also about a new box, again made of acrylic glass.
Btw, for all my detectors I made the enclosure from acrylic glass or ABS plastic sheets. Because I realy like to do them, as small as possible.