Moodz' Awesome Gold Pulse Induction Version 3 - MAGPI V3 Project

[AhmatAhmatov1959]

Slow drift can be a symptom of two things.

The differential amp is overloaded / railed .... the voltage at the oupuf of the differential amplifier U1 should be fairly constant at around 1 to 1.5 volts. If it is closer to 0 or 2.8 volts then the amplifier is seeing an offset current due to ..

1. Leaky input capacitors ... the DC blocking caps must be high quality film caps C6 and C7. Even a very small leakage current will cause an offset DC votage that will rail the output. The integrator caps need to high quality too. Ceramic caps are way too leaky.

2. Overload input ... the samples from the integrators R13, R14, C4, C5 are overloading the input to the amplifier. If the difference between voltage inputs exceeds 150 microvolt approx then the diff amp will overload. Bad sampling windows will do this.

Hello. I assembled Magpi 3. The speaker produces a constant sound that disappears when the target is brought closer. If anyone has encountered something similar, please help. Sorry for my English

[moodz]

Hello. I assembled Magpi 3. The speaker produces a constant sound that disappears when the target is brought closer. If anyone has encountered something similar, please help. Sorry for my English

Please post some photos of the board top and bottom and we will try to assist.

[AhmatAhmatov1959]

Please post some photos of the board top and bottom and we will try to assist.

Hello. Thank you for your reply. I replaced INA125 and it worked. I buy all the parts from ALI. The metal detector has a sensitivity of 20 cm on the hand. On ferrite 15 cm. On copper getinax 50-60 cm. The gold in the photo is compressed foil, it is not an ingot. 3-4 cm. The coil is homemade with a diameter of 20 cm. I made a rope from 44 insulated wires 24 meters long and 0.17 mm in diameter wound 26 turns, left 1 meter at the beginning and 1 meter at the end. The initial meter was wrapped with 10 layers of Teflon tape and put into a heat pipe, and on top I made a screen from the last meter, additionally added 5 wires to the screen for connection to the graphite screen. The Chinese tester showed 280 mcg, 0.4 Ohm and 850 kHz together with the cable, I thought that this was a good result. If of course the tester is not lying. I have several questions for you. 1 What to do with the voltage on the coil. 2 What transistor can replace the BSP230 for higher voltage. 3 How to reduce the influence of ferrite.
I soldered a 120 pf capacitor parallel to the coil but did not notice any changes. Thank you very much for the provided project. I enjoyed making it. Before that I made a Tecoro Lobo, but after 3 unsuccessful coils I decided to do only pulse metal detectors.

[AhmatAhmatov1959]

Please post some photos of the board top and bottom and we will try to assist.

Hello. Please help. The metal detector is very sensitive, it reacts to a hand, a wooden ruler, a plastic ruler at a distance of 20-30 cm. Which screen for the coil would be better, aluminum foil or graphite. If graphite, what resistance should be at a distance of 1 centimeter. The only change I made was the use of LM7171. Thank you

[moodz]

Hello. Please help. The metal detector is very sensitive, it reacts to a hand, a wooden ruler, a plastic ruler at a distance of 20-30 cm. Which screen for the coil would be better, aluminum foil or graphite. If graphite, what resistance should be at a distance of 1 centimeter. The only change I made was the use of LM7171. Thank you

If the coil is picking up your hand then most likely there is no faraday shielding on the coil.

You can use graphite paint ( make your own out of a few drops of varnish mixed with acetone and large spoonful of graphite powder in a glass jar.)
Lay down a very very thin copper wire connected to ground of the coil cable along the coil circumferance ( however do not connect the ends of the copper wire to form a loop !! )
Paint the graphite mixture onto the coil in a thin continous coat ... but leave a gap ( eg 5 mm ) so no loop is formed.

test and reapply graphite if necessary.

[AhmatAhmatov1959]

If the coil is picking up your hand then most likely there is no faraday shielding on the coil.

You can use graphite paint ( make your own out of a few drops of varnish mixed with acetone and large spoonful of graphite powder in a glass jar.)
Lay down a very very thin copper wire connected to ground of the coil cable along the coil circumferance ( however do not connect the ends of the copper wire to form a loop !! )
Paint the graphite mixture onto the coil in a thin continous coat ... but leave a gap ( eg 5 mm ) so no loop is formed.

test and reapply graphite if necessary.

Hello. Is it possible to connect a DD coil? There were no modifications for two years of the project? Thanks for the answer. Sorry for the English

[AhmatAhmatov1959]

Hi Moodz, what is the latest version for LCD display ? If there is, any chance of a copy please ? I'm currently using 1.5 with non working volume.
Thanks

Hello. Please answer. Is it possible to connect a DD coil to this metal detector? If so, how. Thank you

[moodz]

Hello. Please answer. Is it possible to connect a DD coil to this metal detector? If so, how. Thank you

Hi ... The MAGPI is a monocoil detector. Unfortunately you cannot connect a DD coil to the detector without modifying the code and a few hardware changes.
I am not saying its impossible but you would need to separate the RX circuit from the TX circuit and modify the timings.

[AhmatAhmatov1959]

Hi ... The MAGPI is a monocoil detector. Unfortunately you cannot connect a DD coil to the detector without modifying the code and a few hardware changes.
I am not saying its impossible but you would need to separate the RX circuit from the TX circuit and modify the timings.

Thanks for answering. I don't have enough brains to change the timings.

[moodz]

Thanks for answering. I don't have enough brains to change the timings.

well I have an idea in the works .... it will improve things and you will be able to reuse the MAGPI circuit.
Might take a little while .... ( couple of months maybe or sooner if things work out ).

[geoscash1]

Any new info/updates for this project? Is the v3 still the current one being used or?

Is the 1.4 software/source code still the last version with LCD and audio update?

Took a while to find the right thread for this, so many cross ref links all over the forum so sent a pm but found it, I think.

Would like to try this out since Im in Nor Cal and have some pretty hot ground and loads of hot rocks here.

[Technologyh]

I think that. We are waiting and we want to participate

[AhmatAhmatov1959]

Any new info/updates for this project? Is the v3 still the current one being used or?

Is the 1.4 software/source code still the last version with LCD and audio update?

Took a while to find the right thread for this, so many cross ref links all over the forum so sent a pm but found it, I think.

Would like to try this out since Im in Nor Cal and have some pretty hot ground and loads of hot rocks here.

Hello, I ask those who made this project to respond. Are there any mods? Thank you.

[moodz]

It takes a long time to properly test new things in this technology. There are lots of projects which are YAPID ( Yet Another Pulse Induction Detector )...based on established ideas. MAGPI 3 is not a YAPID detector but also is not my day job ... I do work on it when I can but I currently have 4 other projects in hand. Presently I am working on testing MAGPI 4. MAGPI 4 is much improved over version 3 ... For instance it offers full depth discrimination and full auto continuous ground balance. I have spent 6 months converting the 3 model to an ideal mathematical detector in software only. There are no analog processing elements in the detector
..eg amplifiers etc

Unfortunately it is not a built with 555 and 4066 circuits ... My next challenge is to extract precision from simple but elegant strategies that will not require expensive / hard to get components ... Eg high speed precision ADC.

Moodz

[van0014]

I've been exited to make this for a few weeks now. And am taking time to select components. In a spreadsheet I have components, their numbers and their function. I'm hoping to place an order soon

There is only one component I had trouble finding, the BSP230. I want to try SIHFR9310TRL-GE3. I'm not sure if it's suitable and if circuit changes are needed. I noticed some differences (aside from DPAK TO-252AA).

It has higher input capacitance (BSP230: 90pf. SIH: 270 pF).
Drain to source voltage is higher (BSP: 200v. SIH: 300v)
Gate charge (BSP: ~1nC. SIH: 13nC @ 10V.)

In total, parts will be about $185 AUD. I've opted for resistors and capacitors with lower temperature drift. I'm looking forward to trying this out and getting into the field again. After trying detecting for about a year, with GM1000 and the Spectra V3, i'd given up and gradually sold them.

Now with this brilliant machine, leveraging the skills of Moodz' engineering and innovation, I will be more enthusiastic than last time. Knowing that it's no longer the detector that's holding me back. It's my mind, my patience, my inner voice..

Last time it was saying: 'don't dig, it's trash!'. 'Give up!'. 'You could be doing something useful'. 'It's all been found!'.

This time it'll be saying:
'GM1000 has limited settings. This machine has a few settings. I like settings.'.
'There's more to be found. Now you can see'.
'You've got a good detector. Can't blame the machine anymore!'.
'I wonder what's happening in the PCB. Electricity. Capacitor. Resistor. Diode. Pulse. 50Hz, no, stay away from my coil. It's everywhere!'
'Dig it and learn what different targets sound like'

Edit:
I can buy a BSP230 for $40 but am hoping for an alternative with similar performance. BSP225 may be the closest I can get. Hopefully the 50v drop in Vds doesn't affect the circui much