Getting ready to build the MPP

[KRinAZ]

Hey all, this will be my first PI (or any) self built detector project, also first coil build. Looking forward to it! My oscilloscope and multimeter are ready and waiting, ordered the pots I don't have, and waiting on my kit from silverdog - coming via Royal Airmail (now doesn't that sound cool).
I'm currently scrounging around trying to find bad donor PI coils that I can use for parts, & thought I'd use bbsailor's coil build guide, probably a 9 or 10" version as I usually search for smaller gold (but maybe that will change when I start using a PI), my current detector is a White's GMT - excellent detector for VLF! I like how I can tweek sensitivity & SAT speed on it, & turn off GEB, & so why the MPP caught my attention - as I plan to have those (except sensitivity) in my final build, & volume control on the box instead of on each of my headphones (L&R).
One criteria for success for me is to be able to get target response at or especially below 10us delay. I plan to use it for gold prospecting only, already have enough found iron lol - with that in mind I'm sure down the road I will want to take a shot at building a DD coil.

Been lurking and reading the heck out of the MPP Responses forum, think most all of you are light years ahead of me as EE's but I'll try to not ask dumb questions. & yes I'll follow the manual & steps...looking over it the kit itself seems like an easy project (except the coil build) but we'll see how I do. I have more experience with digital circuits than analog...
I'll build the kit as is first and the coil and get it all working, then I want to have mod's fun with; varying the SAT speed, adding GEB, who knows what else.

[WM6]

MPP is a good project, wish you good look with it.

[Silver Dollar]

Well it looks like you are getting the "Royal" treatment!

PI coils are "easy as PI" to make. Look here for a few I've made reciently;
http://www.geotech1.com/forums/showt...f-New-PI-Coils

Making a fast one is a little tougher. I'm not sure if the one shots used on MP will allow
very short delay times?

I bought a board but haven't started acquiring parts yet. I have some stuff but I like to
install all the parts I have then see what I need. On this project you really should build
sections at a time and I ran into not having the LT1054 I have 1044's 1045's 7660's
866's but not 1054's...

Well good luck on the build. I might scrounge up some parts and build it along with you!

[Chet]

Hi KRinAZ,
I have completed the Minipulse Plus (rev C) kit. I am very pleased with the kit and the results.
Follow the build procedures which are very good.
Do not proceed to the next step without successful test results on the previous steps.
A few minor suggested changes; these may have already been updated in your build procedures.
Include the following parts into Step 3, Q2 (2N3904), R9 (10k) and R5 (20k)
Add to Step 7; for testing short PL3 again
Add to Step 8; for testing connect 50k Reject pot to PL3.


I built the coil described in the Coils Forum _ under Chance PI around Posts #110 -----126. It is a very good coil. And the 7.5-8” coil size is a good way to start, it is quieter, gets into smaller places, stays closer to the ground, and still has good depth on larger nuggets. Later I recommend that you not go above 10”, it will miss many small nuggets and is nosier and loses the other advantages of a small coil.
After you have it working read through the Replies to Minipulse Plus forum and try some of the recommended modifications.

[KRinAZ]

MPP is a good project, wish you good look with it.

Thx WM6! I know I'll enjoy this project.

[KRinAZ]

Well it looks like you are getting the "Royal" treatment!
haha ;^>


PI coils are "easy as PI" to make. Look here for a few I've made reciently;
http://www.geotech1.com/forums/showt...f-New-PI-Coils
Oh man, those are some cool coils - if I may ask - are the coil shells still available or did you get them from Hays? & the center tapped coil - is that an approach to have tx & rx coils? I'm familiar with center tapped transformers but those are a different beast...

Making a fast one is a little tougher. I'm not sure if the one shots used on MP will allow
very short delay times?
Not sure what this means - one shots?

I bought a board but haven't started acquiring parts yet. I have some stuff but I like to
install all the parts I have then see what I need. On this project you really should build
sections at a time and I ran into not having the LT1054 I have 1044's 1045's 7660's
866's but not 1054's...
Thx, I definitely will follow the manual and steps exactly, much easier to catch a goof or bad component right then...& I ordered silverdog's kit so will build it with all the spec'd parts in the kit and get it all working before playing with any mods. I'm a big believer in "change one thing at a time and evaluate". I did request the TL071/2 instead of the TL061/2 for better noise specs - maybe at the expense of higher power demand.

Well good luck on the build. I might scrounge up some parts and build it along with you!
Well cool Silver Dollar! I'll let you know when I've got everything together and ready to begin. I think I may get some 28AWG ETFE coated wire (Tefzel wire wrap wire) and mash up a coil so I can at least use it for the build and start practicing on coil builds. The Tefzel is pretty close to teflon for dielectric constant (2.6, vs Teflon's 2.1, so capacitance is fairly low) and 1/2 the price, maybe a good place to start before buying higher $ wire. I'm trying to get some bad Coiltek's to use wire from but don't know if I will land them...

.

[KRinAZ]

Hi KRinAZ,
I have completed the Minipulse Plus (rev C) kit. I am very pleased with the kit and the results.
Follow the build procedures which are very good.
Do not proceed to the next step without successful test results on the previous steps.
A few minor suggested changes; these may have already been updated in your build procedures.
Include the following parts into Step 3, Q2 (2N3904), R9 (10k) and R5 (20k)
Add to Step 7; for testing short PL3 again
Add to Step 8; for testing connect 50k Reject pot to PL3.
Thx Chet, will do on following the steps and testing/verifying each before continuing, & thx on those last 3 tips. Congrats on your MPP build!

I built the coil described in the Coils Forum _ under Chance PI around Posts #110 -----126. It is a very good coil. And the 7.5-8” coil size is a good way to start, it is quieter, gets into smaller places, stays closer to the ground, and still has good depth on larger nuggets. Later I recommend that you not go above 10”, it will miss many small nuggets and is nosier and loses the other advantages of a small coil.
Hmmm, I like the 8" coil idea - if I can get one built nice and fast I could just stick with it. Most folks I know really go for the big coils, but I seem to always like using smaller ones to get in tight spots. My bigger coils get me frustrated when I can't swing for all the rocks I bump into. My hunting grounds usually have lots of bigger rocks & boulders as well as seriously mineralized (of course lots of iron also) ground, took me a while to figure out how to run my GMT nice and smooth and quiet on this ground. & guess I'm not one who covers miles per day with their detector... I'll check out the Chance PI forum on that coil build info...

After you have it working read through the Replies to Minipulse Plus forum and try some of the recommended modifications.
Definitely will do!

.

[KRinAZ]

...I built the coil described in the Coils Forum _ under Chance PI around Posts #110 -----126. It is a very good coil. And the 7.5-8” coil size is a good way to start, it is quieter, gets into smaller places, stays closer to the ground, and still has good depth on larger nuggets. Later I recommend that you not go above 10”, it will miss many small nuggets and is nosier and loses the other advantages of a small coil...
Hey Chet, OK, I've been reading that Chance PI coil post - I'm a bit overwhelmed at the moment, but that's a very interesting coil build (the basket weave thing) and it has the specs I will seek! I don't have the machining tools they are talking about for making the forms and such. Are they available somewhere, or did you make/machine one? Did you fiberglass yours like in the photos? I've never done fiberglass but could give it a try I guess, at least it would solve the problem of finding/making the coil housing...

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[Silver Dollar]

Those housings came from Ebay, there was a guy from Bulgaria selling them there.
They were from this guy, I don't see them listed anymore though...
http://www.ebay.com/sch/mikronbg/m.h...p2047675.l2562

The center tapped coil allows a fast TX (as you drive only one side) and low noise on the RX
(as you use a differential preamp).

You can make an easy basket coil using a jig saw to cut the circle and then just drill holes.
I made this one;


The one shots I was talking about are the 4538's on some PI's they used 74HC221's which had
a minimum pulse width;

[Silver Dollar]

I just remembered DBFlowers sells housings too. I got a couple 9" with covers off of him.
https://sites.google.com/site/dbcoil...10-inch-shells

This is one of his housings;

[KRinAZ]

I just remembered DBFlowers sells housings too. I got a couple 9" with covers off of him.https://sites.google.com/site/dbcoil...10-inch-shellsThis is one of his housings;[ATTACH]31437[/ATTACH][ATTACH]31438[/ATTACH]

Thx! - these are nice, now I know where to get one, I think the 9" would be the first one I would try

[KRinAZ]

You can make an easy basket coil using a jig saw to cut the circle and then just drill holes.
I made this one;
[ATTACH]31435[/ATTACH]

OK, I'm in! I want to make one of these, might as well go for the "gold" and take a shot at building a nice fast self shielding coil right off!

If you have any sources of specific instructions, patterns, howto's that would be great - from what I could tell from the coil building posts, they seemed to assume someone already knows the basics of building these and knows how the form should be made, what materials are used, how to actually correctly wind it, etc.

It appears this coil is too big to fit in one of the pre-made DD coil shells, am I right on that? If so I'm guessing the most popular way to enclose it is via fiberglass work.

I did read that if someone is going to enclose it in fiberglass they use lexan for the form. I would really like to find the specifics on how to make the form, how to wind it, how to fiberglass it and include the pole mounts, etc.

I will continue searching for all this as well...

.

[KRinAZ]

OK, update on the basket weave coil build info - I am becoming obsessed with building one of these LOL so I am putting together specific info and specifically for the MPP - when done I will put in a PDF complete with test results, measurements, etc.

I have found fragmented info on the form build and fiberglassing it. I believe I will be able to put together a layman's howto to build this for the MPP project.

The one thing that still eludes me is how specifically to wrap the wire on the form. I have found where folks have wound it wrong and had bad results, but have not found step by step of how to wind it correctly, could use some help on this...

[Silver Dollar]

Have a look in this thread on how to make the form and how to wind it (look around #111);
http://www.geotech1.com/forums/showt...-PI-coil/page5

That's the easy part, I still haven't figured out how to package it. I saw someone
who packed foam tubes around it then taped and glassed it to male a big donut
type housing. I cannot find the thread just now...

[KRinAZ]

Have a look in this thread on how to make the form and how to wind it (look around #111);
http://www.geotech1.com/forums/showt...-PI-coil/page5

OK, good, thx, I think I have all the info now to learn how to build one and set it up on the MPP.
I'm going to pickup lexan today and practice with string, then build it and measure it with my inductance/capacitance/resistance multimeters - then with the scope when I have a working MPP.
Thx again Silver Dollar!

That's the easy part, (the easy part, yikes!) I still haven't figured out how to package it. I saw someone
who packed foam tubes around it then taped and glassed it to male a big donut
type housing. I cannot find the thread just now...

.