Bipolar PI design

[Carl-NC]

I think the main problem on my detector is that I soldered all the resistors backwards!

That'll make all the currents go backwards. On the bright side, it will charge your battery.

[Detectorist#1]

Hi eduardo,
In the long discussion in bulgarian site "metaldetecting.eu" (from 2023), the author of "Micron Hybrid Smart Pulse" said that this project from the beginning is for middle size objects - preferably coins. He mention that if this project will be modified for small nuggets, the results will be not better than other good detectors.

[Detectorist#1]

Hi eduardo1979,
Maybe Carl will help to us to design hybrid PI detector with stable GB. In the meantime, we will work on this.

[Orbit]

Do you think of the Smart hybrid that often adjust the geb? I don't believe you can copy it, it's a flooded processor and lines to the demodulator. And the commercial detector that is still being sold would be theft, Mikron could sue you.

[eduardo1979]

I totally agree with you, Detectorist #1. My next project will be a hybrid detector with an IB DD coil. I'm about to buy a Hybrid Pulse from Mikron Bulgaria to see how it works and maybe improve it. I'm sure we could solve the ground balance issues with this detector together with an LM393 comparator. I have a friend here in Spain, in a city called Huelva, who has a detector like this, and he told me that it's practically impossible to search in real ground with this detector. The ground balance is impossible to adjust; you'd have to adjust the ground balance every step you take. Anyway... it's a long story, and I don't like to go into too much detail.

[Detectorist#1]

Now seriously,
Ivconic, for your dream for good MD, capable to finding small coins, with good GB possibilities, not with very deep possibilities, maybe mechanically stable coplanar PI-IB coil will do this work. All we, DIY peoples, have to make additional efforts for achieve this dream.

[Detectorist#1]

The solution - desolder all resistors and sold them in right direction! But not today. We have to believe in tomorrow's day!

[ivconic]

I think the main problem on my detector is that I soldered all the resistors backwards!

[eduardo1979]

This is the best way.
Detectorist 1 is right.
Plus, you'll avoid the glitches that occur in the demodulator.

[Detectorist#1]

Hi SHARK_MD,

The simplest way to replace the chip 74HCT4316 is to use CD4066 + additional voltage shifters with transistors as the schematic modified from eduardo1979.
Read this tread from beginning or see attached information.

[SHARK_MD]

Hello friends. I am from Ukraine, please tell me how to replace the chip 74HCT4316?

[Orbit]

I doubt it's the damping resistor. Even when badly damped the early-late sampling mechanics don't change. Go back to post 302. Are you getting correct polarity responses on each channel before the GB pot?

The problem not understanding how the balance of the land Geb actually works. I also don't think it has anything to do with the damper resistor...

[eduardo1979]

Examples.

[eduardo1979]

The main question at this moment is; how is this procedure done on a Bipolar PI detector?

Hello Ivconic.
I've attached a photo of my oscilloscope screen. You'll notice that my coil is well underdamped, as it didn't have a resistance less than 330 Ohms. In reality, I needed about 270 Ohms. I prefer a slightly underdamped coil to sample all the op-amp saturation points. You need to connect the channel 1 probe of your oscilloscope to the VOP output. It's not necessary to measure with both oscilloscope channels. Pay attention to the polarity of the VTXP to R8 and VTXN to R10 connections, as shown in the original schematic.
I hope your detector problem is resolved soon.

[Carl-NC]

I doubt it's the damping resistor. Even when badly damped the early-late sampling mechanics don't change. Go back to post 302. Are you getting correct polarity responses on each channel before the GB pot?