Metal detector for medium-large objects

[Ssoufian]

First thank you Eduardo for that detector I building at home is work well

[Ssoufian]

This one layer

[Ssoufian]

[haylaz0036]

I wonder if it distinguishes between metals?

[tuntunlin]

Greetings, my friend. I would like to know: after you ground-balance your GS5 Lite, does the audio remain stable? And are you using the original LT1114 IC as specified?

[haylaz0036]

The LT1114 IC is very hard to find; I wonder what I can use as a substitute.

[Ruben2000]

The LT1114 IC is very hard to find; I wonder what I can use as a substitute.

You can use the TL084.

[dbanner]

This one layer

Can you share the schematic for this layout? Where can I find it?

[dbanner]

Ok, I think I found it.

[tuntunlin]

Greetings, respected teachers.

I have now reached the stage where my GS5 Lite is assembled and in use. I am not using a factory-made coil but a self-made one. The coil is 300µH with 0.7Ω resistance, and I am using RG-59 cable for the coil cable.

The problem I am facing is that when I use a delay of 10µs or 15µs, the detector sounds off (chatters) when I swing the coil in the air, even before it touches the ground. However, when I set the delay around 22µs, it is stable both in the air and on the ground. The ground balance also works well at that setting.

However, at that setting it no longer detects small gold nuggets.

Earlier, when I had the delay set at 10/15µs, it did detect small gold nuggets. My coil is shielded with 15mm-wide foil tape. Previously I had used graphite shielding, but I did not like it very much, so I changed it.

So my question is: why is it unstable in the air when tested at 10/15µs delay?

Please kindly answer. Thank you.

[tuntunlin]

The LT1114 IC is very hard to find; I wonder what I can use as a substitute.

Please substitute the LT1114 with the TL064. It also works well.
When buying the TL064, be careful if it is a Chinese-made version.

[dbanner]

Greetings, respected teachers.

I have now reached the stage where my GS5 Lite is assembled and in use. I am not using a factory-made coil but a self-made one. The coil is 300µH with 0.7Ω resistance, and I am using RG-59 cable for the coil cable.

The problem I am facing is that when I use a delay of 10µs or 15µs, the detector sounds off (chatters) when I swing the coil in the air, even before it touches the ground. However, when I set the delay around 22µs, it is stable both in the air and on the ground. The ground balance also works well at that setting.

However, at that setting it no longer detects small gold nuggets.

Earlier, when I had the delay set at 10/15µs, it did detect small gold nuggets. My coil is shielded with 15mm-wide foil tape. Previously I had used graphite shielding, but I did not like it very much, so I changed it.

So my question is: why is it unstable in the air when tested at 10/15µs delay?

Please kindly answer. Thank you.

Possible fix:

Changing your coil cable to RG-59 and replacing the shield with aluminum tape alters the electrical properties of your system so significantly that your previous damping resistor value is no longer correct. Leaving the old resistor in place is exactly why your early 10µs/15µs sampling windows are failing.
To fix the chatter and restore your detector's sensitivity to fine gold, you need to recalibrate the damping resistor to match these structural changes.

Replace the RG-59 with a low-capacitance shielded twisted pair cable (microphone or high-quality audio cable)

Re-check the Foil Shield Gap, and make sure it is properly grounded.(Ensure that your foil shield is connected to the audio/signal ground at only one physical point (usually at the control box connector or where the cable enters the coil shell).

Integrator parts:

• Manually Match Resistors: Ensure input and feedback resistors on the stages are matched to within 0.1% of one another.
• Upgrade Capacitors: Ensure the integration loop caps are premium 1% Polypropylene film types.

Maybe these suggestion will help.

[haylaz0036]

This one layer

Hello there; I’ve decided I want to build the single-layer PCB version. I’ve examined the board, but I’m wondering what the potentiometers on it do, and I couldn't find the parts list. Also, does the device have a discrimination feature, and if so, how is it set up? I watched the video and would like to give it a try. Best regards.

[GeoMax]

Hi haylaz0036,

If you want to make a single-layer PCB, be aware that it will either be impractical or end up the size of a dining table. Why do you want to make a single-layer board? I used to etch and assemble almost all my PCB projects in two layers at the kitchen table. By the way, the PCB for the GS5 Lite is already available.

[tuntunlin]

Possible fix:

Changing your coil cable to RG-59 and replacing the shield with aluminum tape alters the electrical properties of your system so significantly that your previous damping resistor value is no longer correct. Leaving the old resistor in place is exactly why your early 10µs/15µs sampling windows are failing.
To fix the chatter and restore your detector's sensitivity to fine gold, you need to recalibrate the damping resistor to match these structural changes.

Replace the RG-59 with a low-capacitance shielded twisted pair cable (microphone or high-quality audio cable)

Re-check the Foil Shield Gap, and make sure it is properly grounded.(Ensure that your foil shield is connected to the audio/signal ground at only one physical point (usually at the control box connector or where the cable enters the coil shell).

Integrator parts:

• Manually Match Resistors: Ensure input and feedback resistors on the stages are matched to within 0.1% of one another.
• Upgrade Capacitors: Ensure the integration loop caps are premium 1% Polypropylene film types.

Maybe these suggestion will help.

Yes, thank you very much for answering my questions. I will go ahead and make the necessary adjustments.