One more variant to create PI MD with reliable Fe reject

[pito]

Is there a video of it, that will help to make a decision to build it or not.

[Orbit]

Hi Orbit,
This unit works exactly at the same way - in the magnetometer's mode TX coils not work.
When you wаnt to know the material of the target - just click the switch to Fe mode.

I didn't understand right away ,that's the best way, although it can be done simultaneously, but it's not so good anymore, I used the coil of the pi detector as a sensor..

[Orbit]

Is there a video of it, that will help to make a decision to build it or not.

If I have a video somewhere of how it works, but it was recorded a bit out of context, I can send it to you privately if you are really interested...

[kt315]

The project is based on information from coil's guru Joseph Rogowski and the patent of Carl Nelson for gradiometer design of PI MD

can you call Joseph Rogowski in the forum? would be nice to read comments of the Guru how to do right balance of VLF coil. IMO.

[Detectorist#1]

Hi KT315,

This is forum for PI technology, maybe not right place to comment the topic of right balance of VLF coil.

[kt315]

hi Det#1

it was just a test from me. his nick is bbsailor.
ast PI coil by Joseph J. Rogowski a good choice for MiniPulse Plus? - Geotech Forums (geotech1.com)
BTW why you refuse to use Search engine of forum?
Help wanted to jog my memory - Geotech Forums (geotech1.com)

[Detectorist#1]

Hi KT315,
Let's to be serious, If you have some comments to my proposal, give them here!
The nick name of Joseph Rogowski is well known for MD enthusiasts from long time.

[Detectorist#1]

Hi all DIY designers,
This project is specially designed for easy repeating from wide detectorist. Don't warry - if you have some questions - ask now!

[Detectorist#1]

Hi all PI MD enthusiasts,

Now, I will change the Rx coils in this project. The SFR frequency is too high (2.55MHz) and this points that I have possibility to make two Rx coils with 24 turns instead of 12 turns. This will increase the inductance from 75uH to 300uH and will have to increase distance of recognizing of targets. The new SFR frequency will be reduced two times, but I hope - this will not affect the distance for small ( one grain size) targets. Tomorrow I will make new Rx coils and will test this idea. You will be informed for the results.

[Detectorist#1]

This change will increase the distance of sure Fe target recognize - this is one of aim of this middle complexity project for DIY people.

[Detectorist#1]

Now I change two Rx coils from 12tr. to 24tr. (75uH to 275uH) and I am supprized from very strong influece
from one round magnet from loudspeaker - very clear signal is recognized from 2.5meters! Now I will change the damping resistors on Tx and Rx coils for seting of new minimal delay in Rx part.

[Detectorist#1]

These days I finished experiments with new Rx coils in this project. The distance for Fe objects is increased two times. This is expected - the Rx coils have two times more turns.
But the serious improvement is the reducing of the number of ICs from 21 to 10. Also the power consumption is reduced and the project use only one PCB instead of two PCBs.
Attached is the new schematic of this project. This project use two RX coils in gradiometric connection - the way of search is different - no holes in the ground are OK. After a signal, you have to use pinpointer for find of exact place of the object!!!

[pito]

Page 3 schematic = consider replace transistors by MOSFET driver such as TC4404/TC4405

[Detectorist#1]

Hi pito,

Two reasons for using of discrete transistors instead of TC4404:
1. The price of TC4404CPA is 3.96USD in Digikey and Mouser. The price of BC337-40 (BC327-40) is 0.11USD (10pcs)
2. The first transistor have two functions - the driver and logical "AND" for the signals "Tx Pulse and Phase"

[Detectorist#1]

Hi all,
Sorry, the type of the diodes D1 and D6 on page 2 is HER208, not HER107. The mistake is a result of earliest tests.