TD3X ( pi )

[DOOLEY]

ah ha,

thank you George !!



I shall have a ponder over it.

[leopard70]

Some more

[nickel_n]

But, unfortunately; my general attitude toward this forum has dramatically changed due some subjective and mostly some objective reasons, and that's why i don't have slightest intention to ever again post here some of the things that i done.
Especially not my pcb drawings. Why not especially pcb drawings? For one very simple reason; i did a lot in the past and was very ready and friendly to share here on these forums. Here and nowhere else.
Also i intend to draw maybe few more versions, because i like Doley's project much! My hat down to him!
So... don't ask for pcb drawings, i will share those only with just very few people here that i have trust in.
Cheers!

P.S.
Doley you did SPLENDID job here!
Your only mistake was to decide to share it here.
You should keep it for yourself only and in time to try to make smaller series and sell to those interested.
In time you will understand my words.

I would like to thank you for all that you offered to the forum and me personally all those years.
I learn allot of your posts. I still am using your coil tutorial as reference.
Unfortunately for me and perhaps others your decision is devastating.
Your PCB’s are the only way that I can put something together,
and have some success at the end.
But I could perfectly understand your reasons.
Thanks again
Nickel

[ivconic]

I would like to thank you for all that you offered to the forum and me personally all those years.
I learn allot of your posts. I still am using your coil tutorial as reference.
Unfortunately for me and perhaps others your decision is devastating.
Your PCB’s are the only way that I can put something together,
and have some success at the end.
But I could perfectly understand your reasons.
Thanks again
Nickel

Thank you! I just wanted to keep sort of "equality" rate between me and the forum.
I think i took much more than i gave here. I can only thank to this forum for what i learned (if learned at all!) from it.
I will not post drawings which i think are "actual" at the time. That's for sure.
But i will not stop giving my support to nice and straight hobbyists efforts here, no way.
In that spirit i will now describe my latest experience with TD3X.
The results with it, i was talking about above, are achieved with 38cm round coil. I was planned that coil for FelezJoo PI.
That particular coil is made from "fat" pvc coated wire. Not with ordinary Cu wire, resin coated, as expected maybe.
Since it was there already; i randomly took it and tried with TD3X. And results were good just as i reported.
Than, yesterday, i desired to make much smaller coil, some 18cm in diameter.
I used ordinary Cu wire, resin coated, 0.45mm, 24 windings, 0.33mH, ~1.2ohms or so.
It sucks! Very bad results! I was surprised at first moment.
Than i realized what could be the problem; it's plain wire and probably huge unwanted inter-capacitance between windings. It will not do.
Higher pulse rate at 1.35kHz as in my case is not allowing me to make coil as i did so many times with PI detectors with much lower pps.
Than i picked up pvc coated wire, randomly from a pile, made exactly the "same" coil on same former.
Somehow, without insisting on exact numbers; i made 0.35mH coil with that wire.
Checked... results were not astonishing but also were much much better than in previous case! Ha! Roughly; results were better for 30-40% or so!
Paradox is in fact that i prepared that coil for FelezJoo PI but never had enough time to test it with it!
So... coil is very important here! Unlike as at PI detectors with low pps where you can skip or add turn or two, use any wire and don't pay much attention on how to make it.
I did my self very bad favor by insisting for years only on slow PI's with low pps and kind adopted very bad habits in coil making process.
Now it hits me back straight to a head! Now i have feeling like i never learned nothing and i must start all over again with PI coils!
I am writing all this to emphasize importance of proper coil making, again. Litz wire, mesh, spider... anything will do if low inter-capacitance is achieved.
Otherwise don't expect some performances.

[Achillion]

If you would like to have your completed MPP project featured in the "Hall of Fame" -> Completed Minipulse Plus Projects by Geotech members
please email me some photos and a description of your experiences with the detector, plus any modifications made.

The same goes for anyone else who has a completed an MPP that's not already in the list.

Qiaozhi, Although I have completed the basic MPP, very soon after I started to experiment and made quite some changes. Basically I split the design in modules so it's easier to make future changes. The detector has a dual supply, uC for the timing and a remote in-coil pre-amp/Tx. I'm happy to post but it is far from the original design.

[Qiaozhi]

Qiaozhi, Although I have completed the basic MPP, very soon after I started to experiment and made quite some changes. Basically I split the design in modules so it's easier to make future changes. The detector has a dual supply, uC for the timing and a remote in-coil pre-amp/Tx. I'm happy to post but it is far from the original design.

In fact, this would make it even more interesting to other Geotech members, as it demonstrates why this project was produced in the first place. The whole idea was to have a well understood good basic design that almost anyone could build, and those who wished to do so could modify it further.

If you can collect all the details together (such as some good clear photos and a list of changes made, plus any experiences and observations) and email them to me, I will add you to the Completed Projects thread. Only provide as much information as you wish. If anyone has any more in-depth questions, I'm sure they'll ask.

[eclipse]

Final version, contains the regular components (almost).

Free boards for DOOLEY, Teleno, Davor and Old cart, If you want, so if you'd like to build it or give the board to a friend, dunno if it works.

Have a quick look if you can, write if you spot something. All decoupling caps will be on the bottom, optional.

I'm starting to build the board for it, there will be promos for the holidays I hope I can order professional boards cheap.

TD3DXM-1.00.pdf

note: fixed front panel non-motion switch - suppose to be on SAT pot.

[DOOLEY]

hello eclipse,

checked over your latest PDF.

R14- NO NEED, REMOVE, DONT REMOVE makes no difference.

R54 that goes to ground,
needs to go to op-amp 1v ref as in my original diagram.
otherwise IC 7.2 will go into inversion.

no need for IC2 12v regulator,
the 7808 can handle up to 36v,
just connect that to battery,
also,
nothing on original design runs on 12v, so no need for it.

notice on your non-motion switch you've written "front panel volume sw"
this switch was on the SAT control, would make more sense there.

feed to Q5 may aswell just go to battery + unregulated.

[eclipse]

Thanks Dooley, I forgot to remove the 12V reg which I added. Added to 1V reference. Components are just stacked for now. The Mosfet will be TO247 because there's a wide choice of TO247 transistors and it's won't be hard to use normal TO220 instead. I'll try to squeeze all connections for the front panel through 1 connector, it may be impossible but doesn't hurt to try. This way everyone can make his own front panel and connect it with a 20 pin cable. Same for the back panel (battery, charger, fuse). Coil will be with its own 2 header holes, probably wider so you can mount the cables with ferrules.

I wounder if it's better to make a heatsink for the 317 reg, or mount it horizontal.

Mosfet diode is TO220-2, again easy to mount other package instead.



TD3DXM-1.00.pdf

[Old cart]

Eclipse, that is very kind if you. I need some time to look at this. I will try to provide feedback within 24 hours. Do you have a proposed layout yet?

[eclipse]

That will be great, I'm planning the board right now and it will be easy to change something at this stage. By layout do you mean sizes?

I need to make the board 100x100 maximum because the cost will be x3...x4 times more even if the size is 1mm higher and will not be able to purchase them at this time,
gift expenses are coming soon and January pockets will be quite empty

I'm thinking size 95x100 mm to fit Hammond & Co boxes (example 1455N1602BK).

[sinclairuser]

hi dooley, remember what i said at the start of this thread?, i knew there would be interest in your design.
well done again, this has really got the forum buzzing.

[Old cart]

Sure, just a few initial suggestions. I do not know how experienced you are in PCB layout so I apologize if I am telling you things you already know. If it is not hard I suggest you break the schematic about half way across and place the second half on the bottom of the page, makes it a it a lot easier to read.
On the layout I was looking for the basic parts placement, however looks like you are working on that now. In general I suggest you place the parts so high currents, like around the coil and drive elements are very close together so as to minimize voltage drops. All the ground circuits should terminate at a single point near the main supply cap. You do not want any heavy currents flow through the same traces that preamp currents flow. Star grounding can work well. For the sampling circuit at the +inputs of IC6.1 and 6.2 it might be good to use guards. These are just loops connected to ground (+4 in this case) that completely encircle the signal path from the switches to the inputs. This will eliminate the effects of leakage on the caps. The caps should be high quality films caps and matched.
I think C42 should be on the speaker side of R52. A high impedance speaker 32 ohms or greater might be a good idea. Add test points at the outpu of each critical signal path. For example preamp, sampler, and any point where revenue voltages, power supply voltages, and offset voltages appear.

[DOOLEY]

hello Sinclair user,

I didn't expect the sudden interest either !!


hello eclipse,

been looking at your latest PDF.

R58 R59 and VR7 is not going to give you an adjustable 1v reference.
done a quick check,
it will only adjust from 4v to 5.3v

try original values :
R58 = 100K
R59 = 10K
AND VR7 = 10K pot.

[eclipse]

Old cart, I have done 2-3 boards for the last 7-8 years and this one has the most components so.. won't be an easy task for me.
The board won't be award winning or anything like that... Yeah I'm familiar with star type ground I guess I will manage to separate ground & power for the Mosfet part and other components, also I've included separate cap for the mosfet part and separate caps for every IC to minimize supply noise.
My primary concern is if I can fit the components in board with 10x10 max size and yeah without deadly mistakes..

Dooley, I will change those values, thanks!