IDX-PRO+VDI

[Sergey_P]

Coil diameter = 20 cm, key saturation voltage = 0.6 V
Q - quality factor of the resonant circuit
F=6,5k
Q / U(L2)/ I*N / N /I, amp/ R3+R(L2)
5 / 21v / 5 / 242/ 0,02 / 204
5 / 21v / 10 / 121/ 0,08 / 51
5 / 21v / 20 / 61 / 0,33 / 13
5 / 21v / 40 / 30 / 1,32 / 3,2
10/ 42v / 5 /491 / 0,01 /419
10/ 42v / 10 /246/ 0,04 /105
10/ 42v / 20 /122/ 0,16 /26
10/ 42v / 40 / 61 / 0,65 / 6,5

[Orbit]

As Karl mentioned somewhere the results of increasing the vpp in tx give results in air, in the ground on some I noticed that the depth remains the same or is increased by a very small amount on others with other rx the sensitivity to both coins and large objects is increased. Depending on the type of soil, if the vpp is too high, it can dumb down the rx and where the mineralization is stronger it gives false signals, that's why I had in mind to put a switch for low vpp and high vpp in the tx. But I go back to what Karl said and the fact that the tx is drastically increased does not mean that the device will be special in the soil. Let's say on the admiral, I used this circuit and tested with standard power a silver coin buried at 20 cm Turkish aspra from the 19th century, the device does not detect it, but when I go with a higher vpp it detects the same coin without problems. I also did the test with 300 grams of bronze Roman coins placed in a ceramic dish at 60cm in the ground at a high vpp detection was excellent! I note that it was perhaps in conditions with very weak mineralization, in some other case the result would probably have been much less dramatic. Yes, the coils were 30cm and 42x36cm in diameter. But in any case it's not bad to have this circuit in a device with a switch so you can see the difference yourself, I forgot some things because these schematics are from 2017 and earlier! I did almost nothing with ib and did not specifically test it .In the last 9 yearsIf I remember this silver coin at 20cm and the size of the little finger nail, the test was with a 27cm coil and the test with 300 grams of bronze coins with 42x36cm. Idx seems to achieve the best results with 27cm and 32cm coils.

[h9361]

As Karl mentioned somewhere the results of increasing the vpp in tx give results in air, in the ground on some I noticed that the depth remains the same or is increased by a very small amount on others with other rx the sensitivity to both coins and large objects is increased. Depending on the type of soil, if the vpp is too high, it can dumb down the rx and where the mineralization is stronger it gives false signals, that's why I had in mind to put a switch for low vpp and high vpp in the tx. But I go back to what Karl said and the fact that the tx is drastically increased does not mean that the device will be special in the soil. Let's say on the admiral, I used this circuit and tested with standard power a silver coin buried at 20 cm Turkish aspra from the 19th century, the device does not detect it, but when I go with a higher vpp it detects the same coin without problems. I also did the test with 300 grams of bronze Roman coins placed in a ceramic dish at 60cm in the ground at a high vpp detection was excellent! I note that it was perhaps in conditions with very weak mineralization, in some other case the result would probably have been much less dramatic. Yes, the coils were 30cm and 42x36cm in diameter. But in any case it's not bad to have this circuit in a device with a switch so you can see the difference yourself, I forgot some things because these schematics are from 2017 and earlier! I did almost nothing with ib and did not specifically test it .In the last 9 yearsIf I remember this silver coin at 20cm and the size of the little finger nail, the test was with a 27cm coil and the test with 300 grams of bronze coins with 42x36cm. Idx seems to achieve the best results with 27cm and 32cm coils.

Thank you dear Orbit for your explanation.
You right, this option can help in some soils with low mineralization.
See attached, i added an extra step for more increasing (20V).
I simulated, no error. Do you see any error?

I want to test three voltages in my panel, 8, 15, 20V.

[h9361]

Yes, the shielded inductor in your link would be perfect.
Yes, look at the LTX waveform. I would put the circuit in LTSpice to figure out the component values.

Thanks.
Dear carl,
Is it possible to see schematic in post #4353?
I added an extra step for increasing voltage, do see any error?

[Carl-NC]

Is it possible to see schematic in post #4353?
I added an extra step for increasing voltage, do see any error?

Usually a charge pump is not a very good choice for the TX power supply, try adding a load and see what happens.

The White's V3 had a "transmit boost" option, which increased VTX from 10V to 30V. It added only 2-3cm of depth on typical coins. As you increase the TX field strength (using any method) the IB null becomes more critical, otherwise you will likely overload the preamp.

[Aleks85]

h9361, what's your goal? Why modify an already good metal detector?
What were the initial parameters of the sensor? Wire diameter? Transmitter amplitude?