New Project - MPS PI - Iron discriminating metal detector.

[dbanner]

Another successful build (for his son) by CBS, who did a lot of the board design for this project. This will be the 7th or 8th successful build of the MPS PI. We have been favoring the Hammond aluminum enclosures for this project.

A question for the Geotech community.. What would make this project more attractive or increase interest? What might impede hobbiests from undertaking this project?
Don..

Nice project. For me, I'd prefer a bright LED to indicate non-ferrous. A plug-in option on the PCB for an LED which can be mounted on a front panel. Sort of like the 1280x aquanaut.
So just a mono tone to indicate the presence of a target and a mono tone + LED to indicate non ferrous. A switch for switching between high tone\ high tone low tone or mono tone + LED.

Also, you might consider an SMD PCB with components as a complete kit along with a ready made search coil and build documents.

[6666]

Hello dfbowers, great project, thanks

[dfbowers]

Sharing the latest component values. Changes here include efforts to closer match the frequency response of the the All Metal and iron Disc channels. The original 1.09 build posted is a bit hotter, more like the Baracuda project with a longer transmit pulse and longer sample. This version is more tame but handles mineralized ground better I think. This version has been tested quite a few hours by C.B. Smith.

Don..

[Detectorist#1]

Hi dfbowers,
Thank you for the further support of your very good idea for hybrid PI-IB detector!!!

[Detectorist#1]

This design crashes the statement for not possible good discrimination in PI detectors!

[GeoMax]

Hi,

for what reason is there a separate power supply for the disc channel?
And what purpose has the bucking coil?

I'm curious what software was used to draw the schematic and PCB. Does someone knows it?
The silkscreen of the previously posted PCB looks also a bit odd, like it was retouched by hand.

[dfbowers]

GeoMax.
The second power supply is not really needed. It just provides some headroom.
As for the bucking coil, it creates an induction balance coil, just like a "DD" coil. A concentric design works much better with this design though. There is no other way to reliably discriminate iron with a pulse induction machine that I know of. It just happens to work well!
As far as the PCBs go, I dont know.. the gerber files are provided if you want to make your own board or modify them.

The schematic is drawn using "Paint" , standard with Windows.
I just Draw basic components, then copy, duplicate and paste.

What city do you live? I was in Germay last week.
Don..

[GeoMax]

Hi Don,

so you use Paint to draw schematics. If you want to draw circuits in the future, you should look at either KiCad or Diptrace. Kicad is a free EDA software. Another good EDA package is Diptrace, which I use. I like Diptrace because it is easy to learn and has all the features to create good PCBs. There is also a free version with some limitations.

[Detectorist#1]

Hi GeoMax,
Your remarks for the type of the program used for drawing of the schematic is not essential (sorry). In this case, the value of the idea is essential!

[GeoMax]

Hi GeoMax,
Your remarks for the type of the program used for drawing of the schematic is not essential (sorry). In this case, the value of the idea is essential!

Hi Detectorist#1

I just gave some recommendations. But it seems like you have never drawn a schematic or made a PCB from a schematic. If you had, you would write differently.

[Orbit]

I don't understand the point of the story at all, whether he has to draw in Dip Trace or specifically some program in order for the project to be good.. A bit funny story.. The brain is important, there is no program that can brain!

[dfbowers]

Howdy folks!
I have been doing a bit of work lately on getting DD coils to work correctly on this design and have met with a bit of success. I see advantages with the DD coil configuration on ground rejection, slightly faster sampling capability, noise reduction and ground coverage and I can run a higher gain as compared to a concentric design. Plus, by sharing the RX coil between the PI and iron disc channels, the DD will pinpoint right down the center of the coil. I still must stay that DIY concentric coils are easier to get to work correctly though. (I guess I just like concentric designs) A 7" concentric is still my favorite!


Note the modification in red on the schematic needed to get the DD coil to work correctly (centerline pinpointing).


My coil values are:
TX - 300uH
RX - 450uH

Coil diameter - 10"
Coil shielding was done with graphite paint applied to the inside of the shell, joined with drain wires to the RX cable shield. I don't know why.. It just works best when wired that way..

Both windings are made from 24 AWG magnet wire for simplicity, just glued to a round sheet of 1/8" hobby plywood, installed in the top half of the shell.
Coil leads are a pair of high quality audio cables.

I have included a pic of a test coil and my completed coil.

Also, note a screenshot of what a correctly nulled coil will look like. If the null is not correct, the iron DISC channel audio with sound raspy or may not work at all.
Channel #1 is the iron DISC channel sample window (DT1) .. and the Channel #2 is the output of the iron DISC channel preamp (DT2).

Anyway, maybe this will encourage others to consider this project. If nothing else, it's a good learning platform for experimenting with the DISC SAMPLE WHILE TX ON method of iron discrimination.

Don.

[phred01]

Is a Gerber files for the PCB available?

[Op04]

Is a Gerber files for the PCB available?

It's already here on this thread. This is a beautiful project..
Many Thanks dfbowers

[h9361]

Howdy folks!
I have been doing a bit of work lately on getting DD coils to work correctly on this design and have met with a bit of success. I see advantages with the DD coil configuration on ground rejection, slightly faster sampling capability, noise reduction and ground coverage and I can run a higher gain as compared to a concentric design. Plus, by sharing the RX coil between the PI and iron disc channels, the DD will pinpoint right down the center of the coil. I still must stay that DIY concentric coils are easier to get to work correctly though. (I guess I just like concentric designs) A 7" concentric is still my favorite!


Note the modification in red on the schematic needed to get the DD coil to work correctly (centerline pinpointing).


My coil values are:
TX - 300uH
RX - 450uH

Coil diameter - 10"
Coil shielding was done with graphite paint applied to the inside of the shell, joined with drain wires to the RX cable shield. I don't know why.. It just works best when wired that way..

Both windings are made from 24 AWG magnet wire for simplicity, just glued to a round sheet of 1/8" hobby plywood, installed in the top half of the shell.
Coil leads are a pair of high quality audio cables.

I have included a pic of a test coil and my completed coil.

Also, note a screenshot of what a correctly nulled coil will look like. If the null is not correct, the iron DISC channel audio with sound raspy or may not work at all.
Channel #1 is the iron DISC channel sample window (DT1) .. and the Channel #2 is the output of the iron DISC channel preamp (DT2).

Anyway, maybe this will encourage others to consider this project. If nothing else, it's a good learning platform for experimenting with the DISC SAMPLE WHILE TX ON method of iron discrimination.

Don.

Thank you dear dfbowers for your project.
I have a question about TL072 (DT2), can i use 5534 instead of it? I know its pins is different, i will change it.