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

[darov922]

darov922 or open to forum,

On this forum is a whole bunch of ideas what to use and not use in building a Minelab coils of any size. Plenty info for what type of litz or stranded tin wire and shielding. The big issue is the cable to the box. You loose all that you gain with perfect coil
if the cable has high resistance and capacitance. One says that he had the cable specially made litz 9 type cable. I have use Mogami cables with my PI coils in the past. This will not work with Minelab coils. The cost is one of the problems. Buying a spool litz 9 is cost prohibitive.
I wish I had the answer. Still looking. Anyone on the forum that has good info that can pin point exactly what to use for coil, shielding and cable to box for Minelab required numbers. Going to China is not the best because you have no idea of quality, fraud and time line. I guess
this is the problem in building your own coils. Minelab 10" mono coil starts at $250 and from there as much $1500 for a coil besides the detector $5000 to $8000. Moodz is attacking the box issue I think. Easy build for his MAGPI V3. More to come with V4.

Hi Rick, thank you very much for your advice, I am aware of the problem with the cable. I want to get a low capacitance wire and place the box as close to the coil as possible. Now I understand why MOODZ uses a built-in coil: it wants to focus on the V3 circuit and not so much on the coil... The cost information is very useful to me, since I have experience building litz wire and 1 meter of the most expensive wire in my country it will never reach 250 dollars... your PCB board looks great... the impedance of your speaker is 32 Ohm? For my version that will have headphones I will have to adapt the filter for 64 Ohm since I will have to place both speakers of the headphone in series...

Dario

[IBGold]

Moodz,

All is now up and running encoder in correct orientation and audio as I like it I finally got the required plugs and sockets and now all wired up I have been playing with it in the workshop and find the encoder locks up now and again and the screen also sometime locks up my impressions are the audio is a bit chattery but this is in the workshop when it stops B----- raining here I will take it down to the beach and around one of the salt lakes and see what happens I have had the other device on those areas so know what to expect.

Regards, Ian.

[IBGold]

darov922 or open to forum,

On this forum is a whole bunch of ideas what to use and not use in building a Minelab coils of any size. Plenty info for what type of litz or stranded tin wire and shielding. The big issue is the cable to the box. You loose all that you gain with perfect coil
if the cable has high resistance and capacitance. One says that he had the cable specially made litz 9 type cable. I have use Mogami cables with my PI coils in the past. This will not work with Minelab coils. The cost is one of the problems. Buying a spool litz 9 is cost prohibitive.
I wish I had the answer. Still looking. Anyone on the forum that has good info that can pin point exactly what to use for coil, shielding and cable to box for Minelab required numbers. Going to China is not the best because you have no idea of quality, fraud and time line. I guess
this is the problem in building your own coils. Minelab 10" mono coil starts at $250 and from there as much $1500 for a coil besides the detector $5000 to $8000. Moodz is attacking the box issue I think. Easy build for his MAGPI V3. More to come with V4.

Rick S,

I have used most of the available Litz wires and found that they all work all I can say on the strand thicknesses is most of the after market manufacturers use 32AWG or .2mm and when I was winding my own Litz I found that was what gave me the best outcomes I have even used the the coil wire to make the coax but it is very time consuming and fiddly at 76 my coil building days have come to a close especially as materials are almost impossible to source in Australia now I have used the red 7mm low capacitance Soundlink Microphone coax its not perfect the strands not being enamelled and slightly more resistive than the OEM cable but it does work in a pinch I will get the cable designation for you when I go out into the workshop tomorrow.

Regards, Ian.

[IBGold]

IAN: really thank you for the information you have given...i plan to make the coil and also the litz wire...although i want to know how many strands of AWG 32 does the 10" ML coil have? i did a quick calculation and to reach the 0.4 Ohms I need 20 wires. Can you guide me a bit, Thank you very much again.

Dario

Hi Dario,

By my calculations you would need around 24turns to achieve around 300 uh and if you are making your own Litz then I would use 33 strands of 32 AWG of solder through enamelled wire I usually wind the the Litz onto the former and add a turn then check with the LCR meter then trim the Litz to achieve the required inductance but remember that when you lace up the coil bundle so that the strands can not move the inductance will rise it is a balancing act.

[Rick S]

darov922 or open to forum,

On this forum is a whole bunch of ideas what to use and not use in building a Minelab coils of any size. Plenty info for what type of litz or stranded tin wire and shielding. The big issue is the cable to the box. You loose all that you gain with perfect coil
if the cable has high resistance and capacitance. One says that he had the cable specially made litz 9 type cable. I have use Mogami cables with my PI coils in the past. This will not work with Minelab coils. The cost is one of the problems. Buying a spool litz 9 is cost prohibitive.
I wish I had the answer. Still looking. Anyone on the forum that has good info that can pin point exactly what to use for coil, shielding and cable to box for Minelab required numbers. Going to China is not the best because you have no idea of quality, fraud and time line. I guess
this is the problem in building your own coils. Minelab 10" mono coil starts at $250 and from there as much $1500 for a coil besides the detector $5000 to $8000. Moodz is attacking the box issue I think. Easy build for his MAGPI V3. More to come with V4.

[darov922]

Rick for your 10" coil try 32/.2 Litz that will do the job for you for larger coils 36/.2 is good. 300 uh and 0.4 ohms are the actual Mindlab specifications any where from .35 to .5 is OK.

Regards, Ian.

IAN: really thank you for the information you have given...i plan to make the coil and also the litz wire...although i want to know how many strands of AWG 32 does the 10" ML coil have? i did a quick calculation and to reach the 0.4 Ohms I need 20 wires. Can you guide me a bit, Thank you very much again.

Dario

[Rick S]

IBGold,

Thanks for the info on ML coils. Greatly appreciated.

[Rick S]

Moodz,
I just realized that I will have to deal with the damping resistor R1 to get proper coil response. I have done the upgrades and the damping option 1. What other
adjustments are there that can be made?
Resistors down on the coil or at the plug where the coax connects to the Pcb? Making a coil close to ML will help a lot tuning the coil to the front end. That is why you are using a 10" mono ML coil.
Still looking at the two loops and how they function together. Still thinking TDI, CS6, Hammer Head and Gold Max.

RickS

[IBGold]

Moodz or anyone else,
I am going down the hard road making a circuit and coil. I will have to try -7v on the -9v regulator (Moodz). I have some left over coils from past PI projects to see what I
have put together works. I have sound coming out of the speaker which is good.
The coil needs to be like ML 300 uh @ 0.5 ohms with at Q of about 2.5? The coil I tried was 301 uh @ 1.89 ohms, Q = 1.00 and shielding 83pf all tested at 1khz. It appears it doesn't work because all
was herd was load noise and no sound difference when metal was moved across the coil. The coil pulled down the 5v and -9v voltage supply by about half. I have read that coil resistance under 1 ohm should work.
I am now under way to make a coil with ML numbers in mind. I am using litz wire 65/36 awg(.125mm) to make a 10" coil. The
Litz wire that ML uses is 72/ .125mm(36 awg)? I am still waiting for my LCD in L.A. distribution center, California. I live in Wyoming, USA.


RickS

Rick for your 10" coil try 32/.2 Litz that will do the job for you for larger coils 36/.2 is good. 300 uh and 0.4 ohms are the actual Mindlab specifications any where from .35 to .5 is OK.

Regards, Ian.

[Rick S]

Moodz or anyone else,
I am going down the hard road making a circuit and coil. I will have to try -7v on the -9v regulator (Moodz). I have some left over coils from past PI projects to see what I
have put together works. I have sound coming out of the speaker which is good.
The coil needs to be like ML 300 uh @ 0.5 ohms with at Q of about 2.5? The coil I tried was 301 uh @ 1.89 ohms, Q = 1.00 and shielding 83pf all tested at 1khz. It appears it doesn't work because all
was herd was load noise and no sound difference when metal was moved across the coil. The coil pulled down the 5v and -9v voltage supply by about half. I have read that coil resistance under 1 ohm should work.
I am now under way to make a coil with ML numbers in mind. I am using litz wire 65/36 awg(.125mm) to make a 10" coil. The
Litz wire that ML uses is 72/ .125mm(36 awg)? I am still waiting for my LCD in L.A. distribution center, California. I live in Wyoming, USA.


RickS

[moodz]

Moodz,
I am using 3 diodes as mentioned. I up the voltage to 12v and -9v issue has been solved. Reading is -8.9v. Thanks for the direction.


Ricks

hmm ... mine works OK on 7 volts.

[Rick S]

Moodz,
I am using 3 diodes as mentioned. I up the voltage to 12v and -9v issue has been solved. Reading is -8.9v. Thanks for the direction.


Ricks

[moodz]

Moodz,
Working with U6 TC4428CPA that generates the -9v supply. I am only coming up with -5.1v on the output of L79L09. My understanding that voltage regulator feeding voltage needs to be at least a few volts above the require voltage.
-9v it would require -10v to -11v volts to keep a steady output voltage. So far the output is -5.1v. U6 pins 5 and 7 outputs are +4.01v. I don't see the necessary voltage for the -9v regulator. Max voltage to the whole pcb is +8.4v(2 li-ion batteries). Checked the orientation and values of diodes, caps many times.
All the other voltages are working fine, +5.0v, +3.2v. Any pointers would be helpful.

Hi Rick ... you probably have the diodes in the inverter configuration ( 12 volt operation ) instead of the double inverter configuration ( 7.4 volt lithium operation ). See post #23 https://www.geotech1.com/forums/foru...820#post409820. The same PCB layout still works. ( 3 diodes only required )
moodz

[Rick S]

Moodz,
Working with U6 TC4428CPA that generates the -9v supply. I am only coming up with -5.1v on the output of L79L09. My understanding that voltage regulator feeding voltage needs to be at least a few volts above the require voltage.
-9v it would require -10v to -11v volts to keep a steady output voltage. So far the output is -5.1v. U6 pins 5 and 7 outputs are +4.01v. I don't see the necessary voltage for the -9v regulator. Max voltage to the whole pcb is +8.4v(2 li-ion batteries). Checked the orientation and values of diodes, caps many times.
All the other voltages are working fine, +5.0v, +3.2v. Any pointers would be helpful.

[jeep6789]

Can anyone upload the test mp4 of this machine?