I've decided to build a simple shallow water metal detector. There are a few freshwater beaches where I live that need searching. I've used land-based detectors on a float years ago, but why not make a water-proof one. I've adapted the basic Bandido circuitry for this. I eliminated the non-motion pinpoint mode. All I need is a good motion discriminator with decent depth. I don't have a lot of room in my enclosure so it's good this circuit will work with only one 9V battery.
The enclosure I chose is from a nearby sporting goods store. It's a small bright orange (goldfish colored) water-proof storage container. I plan on mounting all controls directly on the PCB so there will only be a need for 2 holes in the case; one for the coil cable and one for the headset. I have watertight strain reliefs for those two. Also, I have some small T-nuts that I will glue or caulk to the bottom of the case. This will give me something to mount the PCB to without drilling any holes.
The sensitivity and discrimination pots will mount where the 2 circles are marked on PCB. I won't be able to adjust discrimination once I'm in the water, but I find I don't seem to ever do that anyway. I run with very low disc because of thin gold rings and just scoop up everything. I eliminated the threshold control and made the ground balance a PCB mounted trimmer.
The layout is nearly complete. As you can see, even the 9V battery will mount on the PCB. I have some nylon strap that I will loop though the loops on the top and bottom of the case so I can wear it across my chest and wade with it.
Here is a picture of the case and a 3D rendering of the PCB. I'll post more as I progress. I hope to finish by September because that's when many of the local beaches close to swimmers and metal detecting is allowed.
Merc
The enclosure I chose is from a nearby sporting goods store. It's a small bright orange (goldfish colored) water-proof storage container. I plan on mounting all controls directly on the PCB so there will only be a need for 2 holes in the case; one for the coil cable and one for the headset. I have watertight strain reliefs for those two. Also, I have some small T-nuts that I will glue or caulk to the bottom of the case. This will give me something to mount the PCB to without drilling any holes.
The sensitivity and discrimination pots will mount where the 2 circles are marked on PCB. I won't be able to adjust discrimination once I'm in the water, but I find I don't seem to ever do that anyway. I run with very low disc because of thin gold rings and just scoop up everything. I eliminated the threshold control and made the ground balance a PCB mounted trimmer.
The layout is nearly complete. As you can see, even the 9V battery will mount on the PCB. I have some nylon strap that I will loop though the loops on the top and bottom of the case so I can wear it across my chest and wade with it.
Here is a picture of the case and a 3D rendering of the PCB. I'll post more as I progress. I hope to finish by September because that's when many of the local beaches close to swimmers and metal detecting is allowed.
Merc
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