The Mighty "Fisher CZ5 Quicksilver" and it's secrets

[Skippy]

"5kHz is just right for deep targets and 15kHz is enough good for smallest ones.
I would rather pick 7.7-8.3kHz (SMW&IGSL , Deus) and x3, so 23.1-24.9kHz."

On previous discussions about this, I suggested 13 kHz and 39 kHz ( or 12k / 36k ) , based on 12/13k being good all-round medium freqs for a single-freq machine, for European hunting. Example being the Tek T2 / Fisher F75 at 13 kHz. Decent on the small difficult stuff (15k - 25k targets ) but still competent enough on the milled copper/silver coins ( 3k - 10k ).
One thing that would have made this hard previously was the lack of commercial coils. Minelab's BBS/FBS coils are good to 25 kHz, possibly a bit more.
But now there are the Equinox coils, which we know can work fine at 5 kHz - 40 kHz. Enough is known about the integral electronics board to get the coil working without any issues.

What complicates the CZ machines is the option of saltwater beach settings, and soil (dirt) settings. If the re-design was simplified to just soil, it would help achieve a working design. One of the weak points of the CZ machines is the large number of preset pots that need accurately setting up ... many are 'salt mode' specific, many are 'soil mode' only. Unfortunately no-one except Fisher engineers and 'NASA-Tom' Dankowski know how the machine is supposed to be calibrated, which is a major hindrance to copying / re-purposing the design.

( I am an Equinox owner, so I now have little interest in self-designing / constructing this 'super-CZ' machine, but I thought my ideas may be worth considering for anyone prepared to take on this challenge. )

[Nandor]

Hello friends

The little bulb does not seem to light up when the TX is on. Interesting, i thought that it emmits a faint light. It seems that all the IC's are low power variants.
Some more pcb photos

[ivconic]

Excellent photos!

[ivconic]

Sprint Layout 6 file:

[Riss]

About 15 years ago with a lot of swearing I managed to tune one CZ -5 ( was damaged in the voltage stabilizer , and the owner was spinning trimmers in despair - probably after drinking half a bottle of rakia (brandy).Тhen they joked that you have to change expensive batteries every 100 steps . I keep notes of the instructions for setting up the countless trimmer potentiometers- about a dozen pages . Voltage ratios at control points. I used mineralized stone, a piece of brick, an aluminum lid from a compote jar (type ,, Omnia ??) and 2 Bulgarian coins that have already gone out of circulation .I used two-beam oscilloscope. Precisely because of these coins my setup instructions are useless to anyone who doesn't have these coins . I had another CZ , which worked flawlessly , otherwise I wouldn't be able to do it . Here is a good moment to create an international standard for replacement signals for coins (pieces of metal) - would be useful in many cases . I don't have American or English coins, for example , but each has pieces of copper and aluminum sheet, as well as pieces of lead .

[Skippy]

Riss:
Myself, Eric Foster and Mr. Green did a fair bit of work on targets and their characteristics in some previous threads on here. For unusual targets, such as large ones, you are going to have to create such targets, such as casting lead shapes. But the materials are not consistent, and are often not standardised, either. Alloys are unknown, and this is important, as electrical conductivity can be very dependant on the alloy.
But for small 'coin size' targets, the best targets are real coins. It's just not always possible to agree on which ones, of course. They need to be cheap, no gold stuff. US coins are easy to get in most parts of the world, but there's not much variety or range of metals/conductivities. Euro-zone coins also lack variety.
Here in the United Kingdom, we have a wide variety of metals/sizes, and many of them have identical equivalents used in our colonies, like South Africa, Australia and New Zealand.
Your Bulgarian coins may be easy to buy on eBay ? I have bought a few coins on eBay before, just for detector testing/experiments.

[Nandor]

Sprint Layout 6 file:

Must have been a hard work! I appreciate your help

Riss could you please share your work? I posted these pcb photos so people can see a standard position of the trimmer potentiometers. Did not measured any of them yet with a scope. Im mainly interested in the "Normal" mode, the "Salt" mode is not my priority.
First I have to make some better coils for it. A fellow hobby detectorist and electrician told me that the TX coil should be multicore as the original and also with less parasitic capacitance. Maybe a better TX would make some difference and my CZ5 would work as it should. Trying to document as much as I can. Will post some more scope screenshots also, that tells the most

About the targets, I think that here in Europe many of us are interested in old coins made of silver, bronze or even gold. Modern coins are mainly alloy coins with no real value. My test targets are silver hammered coins and also bronze coins from various centuries.

regards

[Skippy]

I think test targets need to be very repeatable and reproducible. This is where most real dug-up targets tend to fail. Silver hammered coins have the major variable of being made from inconsistent alloys, and varying degrees of corrosion. Bronze coins corrode badly, and not in a consistent way, and they all have much lower TID value compared to circulated but not dug-up examples of the same coin.
Milled silver coins tend to survive better in the ground, with dug-up and regular circulated examples being very similar. So I agree that using them as test targets is not such a bad idea. But the cost needs to be considered. For example the US guys have small silver 5 cent coins 'half dimes' , that would potentially be a useful test target, due to its size ... but they are scarce and collectible, and expensive. ( here in the U.K we have a very similar threepence coin, and they are cheap )
A standardised reproduction of a hammered coin ( or several different ones ) would be useful, it was one thing I was going to look into when I found time ..

Regarding gold coins: I did produce a reasonably good 'equivalent' to a US 1 Dollar gold coin ( 1850's ) a few years ago. 'NASA-Tom Dankowski' seems to think they are a good test target, apart from the obvious flaw that they are really expensive. So I used 'maths and science' to design the replicas, they seemed OK. I sent a couple to Tom D. , he declared them similar, but not close enough. Tilting the coin at an angle gave different results. Maybe the striking of the surface makes more difference than you might think?
Here's the thread:
http://www.dankowskidetectors.com/di...ad.php?2,27267

[Riss]

Skippy , I agree 100% with what you said . Fortunately in the flea markets Bulgarian coins can still be bought . and prices are not high . The coins from the period 1933 -1998 are quite interesting. For example, a 10 stotinki coin issued in 1962 and 1974 copper-nickel alloy has a time constant of less than 15 microseconds . BGN 5 since 1992 has a time constant of over 120 microseconds . Every dealer of metal detectors must have a coin of 50 stotinki -1937 . It has a diameter of 18 mm, a thickness of 1.2 mm, the alloy is aluminum-bronze . With such a coin you can sell even the worst detector - metal detectors "love" her a lot . In air tests, as well as in the soil, this coin registers surprisingly deeply for its small diameter . Years ago I dug one up and almost had a heart attack with joy - I thought it was a gold coin.Аnyone who finds such a coin jumps for joy, but that joy lasts as he looks at it carefully Here are links to this coin https://bg.ucoin.net/coin/bulgaria-5...937/?tid=31292
https://www.olx.bg/sport-knigi-hobi/...BA%D0%B8-1937/
Some coins from Romania are very interesting , because their oscillograms are unique - one would think that the discrimination of his detector was crazy .about 3 years ago Eric Foster bought Bulgarian coins on eBay , and now it shouldn't be a problem .

[Skippy]

HaHa, I too have had this experience - I dug this France '1 Franc' coin from 1922. Surely it must be gold, it's been in the ground 90 years and it's still shiny as anything? But then I felt the weight, very light, oh dear. Aluminium-bronze, similar to 10/20/50 Eurocent coins.
https://www.ma-shops.com/wallinmynt/item.php?id=15895

[Riss]

The simplest solution - small board with 4093 or 40106 - oscillator of 480 kHz , and 4024 - divider of 8. These resonators are cheap, have very good frequency stability, have a manufacturing frequency tolerance, and probably one of the 5 resonators will have the exact frequency of 60, 12 kHz ? Q3 ( pin 9 on 4024 ) . https://www.tme.eu/en/details/csb480...esonators/yic/ . This oscillator can be used (https://www.elprocus.com/crystal-osc...t-and-working/ ) - Colpitts Crystal Oscillator , but you need another transistor to boost the swing to the power rails for normal operation of 4024 .

Тhese wonderful detectors carrying the spirit of the 90 's - they should not collect dust .It is felt that in their development creative inspiration has been invested .The next step in this direction - the oscillogram of current through the transmitting coil of White's DFX ( 3 and 15 kHz ) is a very elegant technical solution .

[Skippy]

Based on the reverse-engineering of the 4.7 kHz / 14.2 kHz mode used on the Deus2 TX signal, I see that this waveform could be applied to the CZ, to create a viable hybrid.
The problems of generating the waveform for the Transmit, and the creation of I and Q demod triggers at both 4.7k and 14.2k ( or whatever) can all be solved neatly with more modern digital techniques.
Either dedicate a microcontroller to doing the signal generation ( lookup table, possibly 120 bytes, using 6 bits of data per byte ?)

Or use a PLD ( programmable logic device ), programmed to behave as a 120-state sequential counter, with 6 outputs used to drive TX and demods, and one master clock input. The clock is likely to be in the 500 kHz - 1.5 MHz range, so a simple common quartz crystal oscillator with 2, 3, 4 stages of binary division beforehand is all that is needed to make all the timing functions. 120 states means 7 bits, so I expect that the timing functions should fit inside a common ATF22V10 ( or equivalent ), or failing that the 'super-22V10' , the ATF750. ( this was a great device when Atmel created it as the ATV750, but it got obsoleted by massive CPLD's. When Microchip took over Atmel, they did a smart thing, and reintroduced it, in modern F Flash format ). these PLD's are 2 or 3 US dollars (unprogrammed ).

If a 5k / 15k TX is used, the Fisher CZ coils should be capable, they may work a bit higher. If you want a higher-freq operation ( 13k / 39 k for example, a good choice ) ,the Equinox coil is an obvious solution. And having the pre-amp internally means the first stage amp inside the 'control box' can be a modest low-noise differential amp, no need for expensive ultra-low noise parts, or discrete/opamp hybrids like in the CZ.

[Altra]

This was my attempt at multi-frequency. I lost interest when the Equinox was introduced and later the Vanquish. But now may revisit the project after a long rest.

It worked pretty good, but was weak on the low conductors. The gain in the harmonic channel needs to be increased to equalize the gain between high and low conductors.

I used the CZ timing as a model, 5khz & 15khz generated by a cheap pic18f1220. It uses a full bridge tx driver to gain the extra coil current. The tx driver is straight from the ML Sovereign. The the rest of the circuit is standard analog. It ignores salt water and has manual ground balance.

[Skippy]

That's a neat looking project, good work.
As you say, the commercial availability of machines like the Equinox/Vanquish ( ACE Apex, others ) make it easy to just go hunting.

Quote:"The gain in the harmonic channel needs to be increased to equalize the gain between high and low conductors."
That's the good thing about the Deus2 waveform - the third harmonic level is about the same as the fundamental, not one-third the level, that the plain square-wave gives.

I've had a look at PLD pricing in U.K. RS components, as an example have basic ( slower ) versions of the ATF22V10 from 56 pence, about 0.80 US dollars. I also found a UK distributor that will supply them programmed from about 4.00 GBP ( 6 US dollars ) in small quantities. The software ( CUPL ) for creating the program file is free, and does simulations/testing, etc, so there's a decent chance the programmed IC will do what it should ..

RS components PLD IC's :
https://uk.rs-online.com/web/c/semic...gic-ics/splds/

[ivconic]

This was my attempt at multi-frequency. I lost interest when the Equinox was introduced and later the Vanquish. But now may revisit the project after a long rest.
It worked pretty good, but was weak on the low conductors. The gain in the harmonic channel needs to be increased to equalize the gain between high and low conductors.
I used the CZ timing as a model, 5khz & 15khz generated by a cheap pic18f1220. It uses a full bridge tx driver to gain the extra coil current. The tx driver is straight from the ML Sovereign. The the rest of the circuit is standard analog. It ignores salt water and has manual ground balance.

Neat work and nice drawn schematic, easy to follow.
Two questions:
1) Why U7 at TX? I understand the role and what it is doing, yet i don't understand why is not used some more simple inverter solution? Cmos.. or two small mosfets... or similar?
2) U12? PIC is supplied with 15v than? Why? Since TX is supplied with 10v.