Minipulse Plus Rev My time has come!

[green]

Tommorow I will paint and make the final mount the coil to the detector chassis...Still haven't figure out the battery compartment...
Anyway,I will take the outer wire insulation from an rg cable to insulate the "leads"coming out of the coil case.I will solder them to an rg62 cable,is it possible soldering affect the coil reading?Also i believe all parameters will change(coil leads+rgcable+rg connectors to MD)is there a way to measure capacitance from inside the detector?For sure I will connect a pot to check for critical damping..and at last is there any ideas how to make TP3 output waveform more stable ?

I would be interested in the final SRF reading of the completed coil with leads attached. Rin is R1. I would try a 4148 across R8 and maybe a 4148 in series with a 500 or 1k resistor across R8 with diode cathode to amp out end of R8. Need to adjusting for best signal at TP3.

[mushaba]

I would be interested in the final SRF reading of the completed coil with leads attached. Rin is R1. I would try a 4148 across R8 and maybe a 4148 in series with a 500 or 1k resistor across R8 with diode cathode to amp out end of R8. Need to adjusting for best signal at TP3.

Will do all first thing in the morning and report back measurements and scope readings...Aside fast coil,I want to make a coil at 300uH that damps with 300-400 resistor..then have it as standard I can go to next step I didn't yet,the coil shielding..I read that some people use kitchen aluminum foil as shield,it's cheap and I'm gonna try it because my order on scotch24 hasn't come in yet..The critical point as I understood is to have space between coil wire and shield right?Also I read that some people make the shield compact and leave a gap 3cm at the end of coil wire exit ,others say that they shield leaving 2cm gaps between each wrap of shield..I will try all of these methods..at the end the coil is the most significant part of a detector...As for the srf measurement green your way suits me fine,I saw a circuitwith two 9v batteries and some parts to get in circuit measurement on oscope..There is also Gary's circuit at the end of the great fast coil paper of bbsailor but I don't have a working function generator at the moment to test it..I wonder if I can simulate the generator pulses with a 555 ..

[mushaba]

1. Picture of two coils I posted awhile back. SRF measured the way I suggested with scope connected to amplifier out of operating PI. Lead wires used between coil and circuit that I have measured have a capacitance of a least 1pf/inch. A 3/4m lead would have 3times the capacitance of the coil. Don't know how fast a 20cm diameter 300uH coil could be made. I think anything around 3MHz SRF without the lead is fast enough. Interested in the specs of coils others have made. Repeated the tests today using procedure reply#110 with scope lead clipped to ground lead making a pickup loop. I've been shorting the not wanted coil when measuring SRF of IB coils(separate Tx and Rx). Tried again today wit the flat radial and flat basked overlapped. Reads close to single coil reading. Maybe there is a better way?

Wow!Great coils green,excellent srf...

[green]

Will do all first thing in the morning and report back measurements and scope readings...Aside fast coil,I want to make a coil at 300uH that damps with 300-400 resistor..then have it as standard I can go to next step I didn't yet,the coil shielding..I read that some people use kitchen aluminum foil as shield,it's cheap and I'm gonna try it because my order on scotch24 hasn't come in yet..The critical point as I understood is to have space between coil wire and shield right?Also I read that some people make the shield compact and leave a gap 3cm at the end of coil wire exit ,others say that they shield leaving 2cm gaps between each wrap of shield..I will try all of these methods..at the end the coil is the most significant part of a detector...As for the srf measurement green your way suits me fine,I saw a circuitwith two 9v batteries and some parts to get in circuit measurement on oscope..There is also Gary's circuit at the end of the great fast coil paper of bbsailor but I don't have a working function generator at the moment to test it..I wonder if I can simulate the generator pulses with a 555 ..

Connect a 500pf capacitor across one of your coils to make it damp with a 300-400 ohm resistor. Don't think a 555 would oscillate at 3MHz. The kitchen foil acts like a target and connecting a ground wire to it can be a problem. The foil can be cut so it wouldn't act like a target.

[waltr]

Waltr
"I said "smaller" gold nuggets. My HH2 will detect natural gold nuggets down to about 5 grams but none smaller."
Is that grains not grams? 5 grams that would be totally unaccpetable to me . stock Mpp revd 1 gram 4 to six inches 6x9 figure 8 coil.

My mistake, smallest gold nugget was 0.5 gram that I ran tests with.
This fits close to your 1 gram @ 4-6 inches.

[green]

Made an error measuring SRF with shield again. Did same thing awhile back, keep forgetting correct procedure. Connected shield lead of test coil to circuit common where it is normally connected. Should have connected it to one of the test coil leads. Flat radial_2.87MHz no shield, 2.475MHz shield to circuit common, 1.74MHz(2mm craft foam spacing each side between coil and graphite shield)1.9MHz(5mm spacing)with shield connected to one of the test coil leads.

[mushaba]

Loading 95% but still not finished...Remains coil critical damping on the detector and possibly another front panel i messed up..A little sneak peek please judge with generocity!



Battery compartment with 3 x 18650 batteries with charging connector...Want to put a BMS inside for correct charging



Didnt have in mind the OD of the pot knobs...I hope the designer doesnt mind putting his name on it..



The build so far. A headphone connector must be placed with a pot....I hope tommorow i will have my fisrt findings!!

[waltr]

Looks good.
Do post pic of your first find.

[mushaba]

Done some testing on my backyard,a very trashy environment due to lots of ironwork done there.I should get it out in to a "clean" environment for field testing..The detector is very sensitive and i believe thats because my 3dss coil is unshielded.Had to keep the coil at 10 cm above ground,gain at minimum threshold at almost minimum and delay early and narrow..The best delay with this setup is 8us (from end of tx pulse until negative curve comes to 0 at TP3). I attach 2 photos om my first find,i believe its a piece of rebar and the coil connector,a bnc T type were i can mount the damp resistor.
Your thoughts please

[waltr]

You found something. I just call this 'a rusty thing' and always finds lots of them.
With actual field testing you get to tweak settings to find what works best.
Then is learning what different targets sounds like for a better guess of what they might be.

Interesting way to do the damping R.

[mushaba]

What about the sensitivity issue?Should I go bigger on coil to reject smaller items since we cannot reject iron?Also is there a possibility EFE to not work as should because of higher operating frequency?

[godigit1]

Looking good Mushaba,

What kind of hunting do you actually want to do? Im getting mixed signals. Small iron will be unavoidable with most all coils. If you tune it out you will loose small gold as well. A fast coil is going to nail small iron all the harder.
The majority of my beach finds are in the sub 2 gram range. And I find allot of earings So many that I know what styles im not hitting due to detectability.
Where I can I hunt Beaches with a Higher Frequency (Gold Bug Pro Or G2 even a GM3). I can find earing backs and studs. With A Pi most of that is untouchable. But Im still hitting paper staples with a 12 inch dual field coil with stock MPP rev d Machine. Iron is very hard to get rid of and if you do you will surly loose small gold.

I will say this about the MPP that Ive used both it and my TDI on the beaches and I use the same dual field coil. That sure I punch way deeper with the Tdi but damn 3 feet for a can will wear you out after a while Plus The TDI is heavy. Hunts are 3 hours instead of 5 barely worth driving to the beach for. I love whites machines but why cant they get ergonimics right they just stay with that obnoxious box sticking out into your side forcing you to hold your arm at a funky angle to get the detector to not wear a hole in your side. Jusus Minelab is lightyears ahead just by turning the box verticle and rounding the corners. Pardon me square box fans .
The MPP hunts slower but is damn good at small targets within the first 1 foot of soil. And nickles at 12 + inches..
You dont have to keep remaking coils you can take a few wraps off one you allready made for experimenting. The other thing always over wrap and remove raps testing with your Lc meter you will probable see 15 to 25uh per wrap come off. You can dial your coil in to the inductance you want.

[Qiaozhi]

Done some testing on my backyard,a very trashy environment due to lots of ironwork done there.I should get it out in to a "clean" environment for field testing..The detector is very sensitive and i believe thats because my 3dss coil is unshielded.
Had to keep the coil at 10 cm above ground,gain at minimum threshold at almost minimum and delay early and narrow..The best delay with this setup is 8us (from end of tx pulse until negative curve comes to 0 at TP3). I attach 2 photos om my first find,i believe its a piece of rebar and the coil connector,a bnc T type were i can mount the damp resistor.
Your thoughts please

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It is more likely that your detector is reacting to the ground due to the 8us delay. The MPP does not have a ground balance control, so you should keep the delay above 10us, and will probably need to increase that to 15us for hunting in the surf on the beach.

[Qiaozhi]

I will say this about the MPP that Ive used both it and my TDI on the beaches and I use the same dual field coil. That sure I punch way deeper with the Tdi but damn 3 feet for a can will wear you out after a while Plus The TDI is heavy.

I'm not surprised that the TDI goes deeper than the MPP, as the TDI is a much more expensive commercial machine, and has a more powerful transmitter. However, the MPP REV-E should be deeper than the REV-D version when adjusted for the beach. In fact, it has comparable performance to Crossbow (an HH variant), which some people have claimed to be as deep as the TDI.

[mushaba]

Looking good Mushaba,

What kind of hunting do you actually want to do? Im getting mixed signals. Small iron will be unavoidable with most all coils. If you tune it out you will loose small gold as well. A fast coil is going to nail small iron all the harder.
The majority of my beach finds are in the sub 2 gram range. And I find allot of earings So many that I know what styles im not hitting due to detectability.
Where I can I hunt Beaches with a Higher Frequency (Gold Bug Pro Or G2 even a GM3). I can find earing backs and studs. With A Pi most of that is untouchable. But Im still hitting paper staples with a 12 inch dual field coil with stock MPP rev d Machine. Iron is very hard to get rid of and if you do you will surly loose small gold.

I will say this about the MPP that Ive used both it and my TDI on the beaches and I use the same dual field coil. That sure I punch way deeper with the Tdi but damn 3 feet for a can will wear you out after a while Plus The TDI is heavy. Hunts are 3 hours instead of 5 barely worth driving to the beach for. I love whites machines but why cant they get ergonimics right they just stay with that obnoxious box sticking out into your side forcing you to hold your arm at a funky angle to get the detector to not wear a hole in your side. Jusus Minelab is lightyears ahead just by turning the box verticle and rounding the corners. Pardon me square box fans .
The MPP hunts slower but is damn good at small targets within the first 1 foot of soil. And nickles at 12 + inches..
You dont have to keep remaking coils you can take a few wraps off one you allready made for experimenting. The other thing always over wrap and remove raps testing with your Lc meter you will probable see 15 to 25uh per wrap come off. You can dial your coil in to the inductance you want.

Hello godigit1.

Im not complaining about anything,my detector works GREAT,at this time the test made on my trashy iron-wise backyard as i say in previous post a lot of ironworks made here over the years leaving lots of iron of all sizes...Its detection range is exceptional (i will make a video with air tests) i say this because the same backyard i scanned with the gti2500 and lots of the small targets found with the MPP when the gti was allmost silent.Its a gold-coin machine and i like to keep it this way as it ment to be..Now about the kind of hunting,im new to all this,here all treasurehunters are looking for ww2 gold,gold coins etc.I will preffer a build in the future with ground balance and discrimination if possible..I just want my MPPtuned for small gold and to do that i should take it on a "clear" environment to test it and see its behavior...Also have Svens Mirage and KT's Delta Pulse Legend on hold..Also i ordered some CrossBow revC pcbs from jlpcb...

It is more likely that your detector is reacting to the ground due to the 8us delay. The MPP does not have a ground balance control, so you should keep the delay above 10us, and will probably need to increase that to 15us for hunting in the surf on the beach.

Hello George,at first thank you for designing a great detector and i dont know if you mind that i put your name on my MPPs front panel..I thought about the reaction with ground and i will follow ALL of your initial instructions about timmings.Also i should have started as the instructions said with a simple bundle mono coil but i didnt understand the hole shielding thing,so i tried the easiest,the 3dss that doesnt need shield.I will calibrate to the original timmings and i will get back with scope readings and photos.

Last to be said i know i was a GREAT GREAT pain in the *** for all of you and please accept my sincere apologies but believe it or not i've allready gained my piece of treasure and that is KNOLEDGE i did not have before,not saying now i have but im nothing like me on my first post..The MPP was a great school from me to begin working with detectors.I hope for all help and guidance from now on from all of you.

Feels like a "final" post but its not,i will try to make my MPP better,i will follow all advise and modifications made on site and im willing to help in anyway i can,only thing im asking is guidance because tons of great things are written in this forum but also imagine a rookie diggesting all this info,that is make my mind spinning like waltr said before.