Bipolar PI MD with GB and DD Coil

[AhmatAhmatov1959]

Hi Ahmat,
For equal positive and negative peek voltage, the sum of Rds of N-ch MOSFET + R34 have to be equal to the sum of Rds of P-ch MOSFET + R15.
What is this strange duration of 3us? What is the value of R57 when TX pulse =100us?

Hello, Detector #1. Please respond. There's a NULL mark next to trimpot R12. What does that mean?

[Detectorist#1]

Hello Ahmat,
The name of this trim-pot is RT2, not R12. With digital voltmeter on 200mV range, with this trim-pot the voltage on pin6 of U5 have to be set to 0V. For eliminating of the AC noise, the POT RP2 "GB" have to be removed during this action.

[AhmatAhmatov1959]

Привет, Ахмат!
Этот подстроечный резистор называется RT2, а не R12. При работе цифрового вольтметра на диапазоне 200 мВ напряжение на выводе 6 микросхемы U5 должно быть установлено на 0 В. Для устранения помех переменного тока необходимо снять потенциометр RP2 "GB" во время этой процедуры.

Привет, Detectorist#1 . Мои китайские микросхемы имеют чувствительность в воздухе к 5-граммовой медной монете на расстоянии 20 см. Это нормально, или её можно улучшить, повысив напряжение до 9 вольт? Когда я сделал первую плату, она реагировала на мою руку, а теперь нет.

[Qiaozhi]

Привет, Detectorist#1 . Мои китайские микросхемы имеют чувствительность в воздухе к 5-граммовой медной монете на расстоянии 20 см. Это нормально, или её можно улучшить, повысив напряжение до 9 вольт? Когда я сделал первую плату, она реагировала на мою руку, а теперь нет.

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[Detectorist#1]

Hi Ahmat,
This result is good but try to increase the distance by more exact set of the noise level on pin 6 of U5 (200mVpp) with trim-pot RT1.This have to be made with oscilloscope. Set him to 200ms/div and 50mV/div. Also, the distance depends from the size of the search coils. What is the exact type of used coil?

[AhmatAhmatov1959]

Hi Ahmat,
This result is good but try to increase the distance by more exact set of the noise level on pin 6 of U5 (200mVpp) with trim-pot RT1.This have to be made with oscilloscope. Set him to 200ms/div and 50mV/div. Also, the distance depends from the size of the search coils. What is the exact type of used coil?

Hello Detectorist#1. The coil is a 22 cm diameter ring. I accidentally connected the 12 V supply in reverse polarity, and everything went wrong. I'm starting over. Check the oscilloscope; I can't get the pulses to match. I've changed the microcircuits, capacitors, and resistors. The voltage on the power supply microcircuit is the same, between -9.4 V and +9.4 V.This is from pin 2 of the CD40106 microcircuit. Thanks for your help.

[AhmatAhmatov1959]

Hi Ahmat,
This result is good but try to increase the distance by more exact set of the noise level on pin 6 of U5 (200mVpp) with trim-pot RT1.This have to be made with oscilloscope. Set him to 200ms/div and 50mV/div. Also, the distance depends from the size of the search coils. What is the exact type of used coil?

Hello Detectorist#1 there seems to be an error in the circuit. Capacitor C41 is connected to -8 volts. I'll check this evening.

[Detectorist#1]

Hi Ahmat,
This is not error. All voltage threshold levels of 40106 IC are given as voltages between inputs and pin7 (Vss). No connection of the 40106 to GND. If you connect C41 to GND, will be big jitter in output signal of U9A. The source of this jitter will be all parasite AC signals on the GND traces of the board.