Bipolar PI MD with GB and DD Coil

[pechkata]

In my opinion, both Detectorist#1 and Geomex are excellent people who have shared their work and effort over the past year and a half with other forum users. Detectorist#1 is a brilliant electronics engineer who has been posting his projects on this forum for quite some time.

I didn't see any like that.

He is an engineer—but not in metal detecting.


You need a bit of practice, too.

[Detectorist#1]

Yes, this is the raw true, we all continue to learn. Just pechkata knows all for metal detecting.

[algan]

Hi algan,
Read please again #189 and the information for the sensitivity. The PI detectors for 80-90cm depth use other size and type of search coils - this have to be known from you as you are on GURU level.

I have a friend who owns a GPX 5000, so I have no problem testing it with different search coils, but I want to see your ground test first. .The GPX 5000 has quite impressive results, so I can gauge what the difference is compared to your detector.

[Detectorist#1]

Hi algan,
As I wrote in #189 and in remarks on the schematic, this project work with ready-made 15x12" SEF DD coil from Bulgarian DETECH company for MINELAB GPX,GP &SD PI detectors. This project NOT work with different type of coils. It is not correct to compared two detectors, one for 500USD and the other for 5000USD.

[algan]

I meant that there are coils of different sizes, for MINELAB GPX there is also one that should work https://www.thrace-detectors.com/nf-mono-25-bg I am looking forward to the video you promised. Thanks.

[moodz]

Very good project. I recommend that we don't compare apples to oranges in the fruit shop if you are looking for bananas.

[boilcoil]

I meant that there are coils of different sizes, for MINELAB GPX there is also one that should work https://www.thrace-detectors.com/nf-mono-25-bg ...

This is a monocoil. The project in this thread works with inductively balanced coils.

[algan]

This is a monocoil. The project in this thread works with inductively balanced coils.

Yes, this will work for this project https://www.thrace-detectors.com/en-...%20finder%20dd

[pechkata]

Yes, this is the raw true, we all continue to learn. Just pechkata knows all for metal detecting.

Metal detecting and a metal detector are two different concepts.

Two different sciences.

[Detectorist#1]

Hi algan,
Have only two problems to use this DD coil: now this product is "out of stock" and the price is 740 Euro. But no problem if you check the possibility to be used with "Dual Tone Pulse Detector".

[GeoMax]

Hello,

if anyone is interested in a Detech 15x12-inch SEF DD coil for this project and doesn't know where to get one: take a look here at eBay. The price of €170 is reasonable, the quality is really sollid and good. Shipping from Bulgaria was also fast, though it may depend on your location.

[Detectorist#1]

Hello,
This is video with "Air Test 1" of "Dual Tone Pulse Detector". The targets are 1x1inch Al piece from beer can, two types of coins and some Fe targets.
Next video will be with targets in the ground.
https://youtu.be/gE5glKX-htQ

[Op04]

Hello,
This is video with "Air Test 1" of "Dual Tone Pulse Detector". The targets are 1x1inch Al piece from beer can, two types of coins and some Fe targets.
Next video will be with targets in the ground.
https://youtu.be/gE5glKX-htQ

Hi Detectorist#1,

Thank's for the update, a powerful machine!
I have some question, since I need a high power version of this (big and deep target)
1. By using GPX5K DD coil, for both R32/63 to get more coil current using S mode, what is the lowest R possible?
2. To increase tx pulse above 70us (at 140us) will std GPX coil survive, assuming I use lower freq to 1.5khz
3. I can't find at local shop 500V P channel, can I use lower breakdown like IXTP26P20P pair with IRFB4227?
I can't help myself not to ask, I'm sorry if this too early.

[Detectorist#1]

Hi Op04,
This project uses ready DD coil, ready S-stick from Minelab and ready metal case from HAMMOND. All this is pointed to easy repeating of the project from people with relatively low experience in MD.
You want to design a detector for bigger and deeper targets. The DD coils aren't suitable for deep targets. They are more suitable for harsh environments. But you may use bigger DD coil with 18x15" size instead of 15x12" size. You may to buy 18x15" SEF DD coil for Minelab GPX/GP/SD and White's TDI detectors for only 183Euro from detechdetect.com from England.
R32 and R63 not limit the TX power in this project. The average current thru these resistors is only 60mA and the voltage drops are only 0.06A x 3.3R = 0.198V. For the increasing of the TX power you wants to increase the duration of the TX pulse from 70us to 140us. This will increase the max TX current appr. two times and will increase the max Drain voltage appr. two times. For reducing of the peek Drain voltage to 450V, you need to reduce the values of the R31 and R35 (the replacing of MOS transistors with parts with lower max Drain voltage isn't good idea). Lower values of R31 & R35 have as result increasing of the min DELAY time and loose of the possibilities to see some low size targets. This project not use heatsinks on the two power MOS transistors and for avoid of overheating you have to reduce the frequency of the oscillator from 2KHz to 1KHz or lower. This is not so dangerous in PI detectors (especially in bipolar TX designs). Some PI detectors works at 100/120Hz.
All semiconductor parts I buy from mouser.com, digikey.com or uk.farnell.com. This helps to avoid the problems with fake parts. Local shops aren't enough.

[Op04]

Hi Op04,
This project uses ready DD coil, ready S-stick from Minelab and ready metal case from HAMMOND. All this is pointed to easy repeating of the project from people with relatively low experience in MD.
You want to design a detector for bigger and deeper targets. The DD coils aren't suitable for deep targets. They are more suitable for harsh environments. But you may use bigger DD coil with 18x15" size instead of 15x12" size. You may to buy 18x15" SEF DD coil for Minelab GPX/GP/SD and White's TDI detectors for only 183Euro from detechdetect.com from England.
R32 and R63 not limit the TX power in this project. The average current thru these resistors is only 60mA and the voltage drops are only 0.06A x 3.3R = 0.198V. For the increasing of the TX power you wants to increase the duration of the TX pulse from 70us to 140us. This will increase the max TX current appr. two times and will increase the max Drain voltage appr. two times. For reducing of the peek Drain voltage to 450V, you need to reduce the values of the R31 and R35 (the replacing of MOS transistors with parts with lower max Drain voltage isn't good idea). Lower values of R31 & R35 have as result increasing of the min DELAY time and loose of the possibilities to see some low size targets. This project not use heatsinks on the two power MOS transistors and for avoid of overheating you have to reduce the frequency of the oscillator from 2KHz to 1KHz or lower. This is not so dangerous in PI detectors (especially in bipolar TX designs). Some PI detectors works at 100/120Hz.
All semiconductor parts I buy from mouser.com, digikey.com or uk.farnell.com. This helps to avoid the problems with fake parts. Local shops aren't enough.

Thank you for explaining in such informative way...wish you always in good health