Lrl from Italy

[liudengyuand]

I successfully detected a copper coin with a diameter of 2 cm, buried for 6 years, at a distance of 4 meters, and a depth of 30 cm, but the output of lm358 is unstable. As time increases, the machine always automatically alarms to prove the sensor The output voltage is rising automatically, so I have to adjust the critical point of 358 frequently.

[tasmen]

I successfully detected a copper coin with a diameter of 2 cm, buried for 6 years, at a distance of 4 meters, and a depth of 30 cm, but the output of lm358 is unstable. As time increases, the machine always automatically alarms to prove the sensor The output voltage is rising automatically, so I have to adjust the critical point of 358 frequently.

https://www.longrangelocators.com/fo...postcount=2558

[brain]

I successfully detected a copper coin with a diameter of 2 cm, buried for 6 years, at a distance of 4 meters, and a depth of 30 cm, but the output of lm358 is unstable. As time increases, the machine always automatically alarms to prove the sensor The output voltage is rising automatically, so I have to adjust the critical point of 358 frequently.

Did you find it with the circuit diagram I sent?

[ERDOGAN37]

help !!!

hello,
can you give information about the coil value?
best regards...

[FrancoItaly]

This is not my lrl, you better open a new thread so as not to get confused.

[ERDOGAN37]

hii

Can you share a gold lrl project that you are 100% sure of.

[FrancoItaly]

Can you share a gold lrl project that you are 100% sure of.

I don't know of lrls that only work for gold.

[FrancoItaly]

I am working on the 100 Mhz version and I do not use a module but a transistor oscillator with frequency command with varicap diode, I do not use a coil printed on the pcb, but a flat coil placed horizontally, while on the sensor stage an equal coil but placed vertically , with the aim of minimizing the transmission of the signal from the oscillator to the sensor stage. In this way, a good result is obtained by keeping the oscillator about 7 cm from the sensor stage. As soon as I have finished drawing the scheme I will post it.

[liudengyuand]

At least you need to know the inductance value of L1 to roughly determine the resonance frequency with c10. This requires a high-precision inductance meter.

[FrancoItaly]

At least you need to know the inductance value of L1 to roughly determine the resonance frequency with c10. This requires a high-precision inductance meter.

There is a simpler system, just build the two coils, oscillator and sensor stage, the same and check the output of the sensor stage (DC voltage). When the maximum value is obtained, it means that L1 / C10 is in resonance with the oscillator.

[liudengyuand]

This is a good way

[liudengyuand]

I think your oscillator should be shielded by a tin box separately

[FrancoItaly]

I think your oscillator should be shielded by a tin box separately

Of course, but we must not forget that even the power must be decoupled.

[liudengyuand]

The biggest problem is that the specific frequency responds to the metal, or a certain frequency, or any frequency,

[FrancoItaly]

The biggest problem is that the specific frequency responds to the metal, or a certain frequency, or any frequency,

In my opinion there is no specific frequency for metals, the phenomenon exists in a wide range from Khz to infrared. All that remains is to experiment and it is very important to have a field where to do the tests, it is necessary to bury the metals, for example gold / silver and wait at least a few months or less, it depends on the type of soil.