Magnum on steroids!

[ivconic]

It all started with this:

Magnum Metal Locator

by Andy Flind

This project was published in the August & September, 1980 issues of Practical Electronics. An add-on board for modifying the mode switch function was published in 1981. The Magnum is a VLF design with ground balance and a TR discriminate mode, but lacks a motion ground balance/discriminate mode. Thus far it is the most advanced hobbyist metal detector project I've come across, amazing considering the date of publication. In 1980 the Magnum would have been a fairly advanced metal detector, just one step behind the motion discriminators that were introduced only 2 years prior...........

[ivconic]

... and than ended with: "Wave", "Golden Mask", "Pirate", "Blisstool", "Admiral", etc...etc....
This is the end of days for analogue metal detectors.
All what could be done; is done already.
World moved to DSP almost two decades before (probably even more earlier).
As these forums are mainly oriented to hobby side of this story; so far we did dozen pretty interesting projects on this and similar subjects.
Maybe it is time to end up with probably most interesting analogue design so far?
It is based on Magnum.
It is versatile and tolerant on numerous mods.
It can work on wide frequency range.
It can be adapted for wide range of coils.
It's performances are competitive with most modern market hits.
People are loving it.
It is made and sold in many variants and versions.
It is not simple to made but also not that hard too.
A bit skilled hobbyist can make it with medium effort.
It belongs to nobody and everybody actually, lot of people added own contribution to its final design.
It is about the time to be published here...

[ivconic]

[ivconic]

a bit more simplified version:

[ivconic]

I made "mag_redu_pcb" version, which is SMT (Surface Mounting Technology) or SMD (Surface Mounting Device) version.
But unlike the "mag_compl_pcb" version; here at "mag_redu_pcb" version: i used 1206 sized SMD components.
I did that for one simple reason; to be able to solder them manually.
1206 sized SMD components are just about "human" enough to be manipulated and soldered by a common hobbyists.
For those with much better sight and more calmer nerves: the fist one; the "mag_compl_pcb" version will be also alright.

[ivconic]

And than... just when you think is over... it is NOT!
I also made a TH (Through Hole) version too!
Most of the hobbyists will like it!
But PAY ATTENTION ON THIS:
as always; during the pcb drawing i was exhausted and therefore i made several mistakes!
Don't panic! I just missed to place and trace few components!
PCB can be done the way it is and later those components may be easily added, with no problems at all... the same way i did it.
So... this TH pcb is made and those missing components are later added over and the "thing" is working just alright!
I marked on schematic those missing components within circles...

[ivconic]

So i made one TH device and right now i am uploading demo video on Youtube, later on i will post it here.
...
Than month later i made second one TH... and guess what?
I made mistake; i made it "mirror"-ed!
Not the first time in my life to do such thing.
But "show must go on", so despite that it was "mirror"-ed; i finished it!
And of course it is working just nice too!
I am explaining this in advance, to avoid any confusion when you see the photo:

[ivconic]

[ivconic]

Last winter a friend from this forum, Eclipse; gave me pretty useful information about cheap and HQ pcb manufacturer!
THANKS AGAIN Eclipse, you were right about them!
So they made two batches of pcb's, one for the mag_redu and another for the SMW_SMT (another story for another topic... maybe).
Those guys indeed did the SPLENDID job !
Here is the photo and bellow is the link:




http://www.elecrow.com/services-pcb-...-c-73_116.html

[Geo]

Hi Ivica.


How is the performance of these detectors???
I have construct both of them before years but i was not so pleased
Magnum was a little unstable and SMW had not good discrimination.

Regards

[ivconic]

A few words on coils...
Those who already made attempt on "Wave" and "Admiral"; may not need additional infos on coil making.
Pretty much the same story here... you may use the same coil data.
Magnum TX&RX front ends are pretty tolerant and you may achieve nice results with variety of coils...
But on Golden Mask version of coils there is pretty nice little thing that author of Golden Mask did!
My hat down to that!
There is additional winding or few, continuing from TX coil (over the TX coil too) and later fed up to sync demodulator.
Depending on size of a coil; additional resistor maybe presented to.
It's all about to trim a bit more precisely the phase and current for sync demodulator.
So... you may wire up your coil either ways; the "traditional" one and the "Golden Mask" one.
In second case you will achieve more precise and more stable Disc&GEB ranges, so i will rather suggest the second one, the way it was done at Golden Mask coils.
Detector can run equally nice in frequency range; 8-18kHz (probably even a bit wider) with the same setup and the very same coil!
Only thing what you have to do is to change the TX LC tank capacitor.
Most common data for the coil are:
- RX = 5mH - 7mH, 18 ohms - 30 ohms
- TX = 0.6mH - 0.8mH, 2ohms - 4 ohms
- TX capacitor = 100nF - 470nF

[ivconic]

Hi Ivica.


How is the performance of these detectors???
I have construct both of them before years but i was not so pleased
Magnum was a little unstable and SMW had not good discrimination.

Regards

You are correct about both you mentioned; Magnum indeed needed an improvements and SMW is pretty "thin" with discrimination (though it can be improved too).
But this version of Magnum which i am presenting here is much much better in all the aspects!
As i said before; most probably this is by far the best complete analogue VLF I/B hobby metal detector project ever posted on Geotech forums.
It is very deep. It has SPLENDID recovery speed. It has excellent GEB behavior.
And last but not least; the DISC is pretty alright.
Disc is not pretty "stiff" and "hard" as maybe on Tesoro's, but than again there is a major advantage in that; it is complete immune on "masking" problem and very effective on smallest targets.
With 2 tone feature turned ON, you don't even need a DISC to be "stiff" at all.
Two tone option is done very good! And i mean it!
Far better than any other "2 tone" design that we've seen so far on these forums, trust me on this!
This "thing" works indeed very good on real soil and under the real natural conditions.

[Geo]

Believe me i tired to construct and try MDs....
But if winter is heavy then maybe to give it a try....
Every time i say .... this is the last construction.... but always coming something new...

Regards

[ivconic]

Believe me i tired to construct and try MDs....
But if winter is heavy then maybe to give it a try....
Every time i say .... this is the last construction.... but always coming something new...

Regards

Same situation with me!
I guess it's been too long in my blood and now there is no cure from it.
I did this last winter.
But i let the things "sleep over night" and much later i am ready to share them in public.
Usually when i lose "the focus" and interest for it.
And besides; these forums "died" again... every once in a while forums simply dies!?
Low activity, lot of annoyance, lot of repeatings. No fresh projects.
I guess it is time to shake it a bit with something interesting... apart from usual spitting disputes.
For long time i was persistently against SMD hobby works. Way too long, i guess.
This was just an attempt to overcome that situation and try to do something fully SMD on my own.
I discovered that i can live with SMD 1206 ...

[ivconic]

So... while i am still in a good mood to spill the treats all over the place... here is another one: