GPZ homebrew coil

[6666]

6666 what makes me think the Minelab one is the same as the Amidon one, is that the actual Minelab one has a clear side, and the Amidon Type 6 is also yellow with a clear side.
T130 is the size and it matches in that respect also, so I'm pretty convinced that an Amidon T130-6 will get you a very close if not a replicate toroid.

Having said that, your toroid may be another manufacturers offering of the same part.
Here's a pic of the genuine model with the clear coat side showing.
[ATTACH]50782[/ATTACH]

Thanks now I see your picture it matches , mine has that "clear section " on the back.

[Kev]

Green do you remember having any tx overshoot issues on your opposing model?

With ZVT there's some serious TX edges, by splitting your RX in half and placing a half on each side of the TX, the tx signals on the RX are 180 degrees apart and somewhat cancel in an adding arrangement.
I'm just figuring this mentally so could be wrong.

[green]

Green do you remember having any tx overshoot issues on your opposing model?

With ZVT there's some serious TX edges, by splitting your RX in half and placing a half on each side of the TX, the tx signals on the RX are 180 degrees apart and somewhat cancel in an adding arrangement.
I'm just figuring this mentally so could be wrong.

Don't remember. Been a long time since I played with DOD coil. Including the chart why I think Rx could be adding. https://www.geotech1.com/forums/atta...3&d=1433907028 (With target at 12inches, Rx adding gave a good signal. Rx opposite a lot less signal(no signal charted with target at 12 inches). I could be missing something. My Tx and Rx are on the same plane, mine is made with magnet wire.

Would think bouncing a target over the center and at 1/2 the radius should show how it is connected.

[Kev]

Thanks for your reply Green.
Hopefully today I'll get time to hook up my 19" to a front-end circuit then I can scope the RX, and by comparing that with your results, I should be able to know definitely.

[6666]

Thanks for your reply Green.
Hopefully today I'll get time to hook up my 19" to a front-end circuit then I can scope the RX, and by comparing that with your results, I should be able to know definitely.

Thanks for doing this.

[Kev]

Thanks for doing this.

The worse thing about the internet is, it's too easy to demonstrate to all the world how intellectually deficient I am, is this why I had trouble at school juggling spatial shapes in the IQ test.

Yes the coils maybe adding on the junction PCB but without flipping one coil they are opposing. I need to check if this affects my inductance measurement for the RX coil it may be out a bit.
I should've advertised to buy a dead coil to butcher. I made a mistake with the wire too, it's on a slow boat from China. As long as I have a coil for when the snow melts it will be fine.

[Kev]

Well still in bed, too cold to get up, I've been surfing and checking out our Russian friends, and they have been making super ds for their digital sinewave machines for years. So they connect their RX pair serially and in phase, so adding as we thought Green.

I'll link to a site, it translates into English if you're using chrome.
Had to chuckle at some if the conversions "I don't know where the dog is buried" I think this says I don't know where the fault is, and "the vodka is good but the flesh it stinks" I've seen this one before, it's a quote of, the spirit is willing but the flesh is weak, certainly the flesh is weak this morning and the wife is getting touchy, time to get up and eat my roast lunch.
This site is good it allows guests to view attachments.
https://forum.cxem.net/index.php?/to...0%B2/#comments

[6666]

Thanks for the link, will have a look at what our Russian friends are up to.

I have been awake all night, its 2:00pm in the arvo now getting a bit tired, might have to have a nanna nap

[Kev]

6666 I hope you're well, and not burning the midnight oil due to any sickness?

Thinking of those various strange translation terms I encountered on the Russian sites has impressed upon me just how ridiculous the computer/brain analogy is. We are far more complex than any computer, even a quantum one, speed is no match for discernment. What a massive task it would be to program AI to recognise let alone respond to contextual idiom, as has been demonstrated by these translators, but that's just the start, what about jokes, hyperbole, and of course empathy, history well underlines the damage sociopaths have rent, God help us if AI gets a free hand in society.

Anyway, I hooked up the GPZ-19 to a small TX circuit peak I=750mA and did some target waving.
Close to the coil there are 4 positive responses, the inner 2 being the strongest as you'd expect with 2 DDs back to back, and there were 3 nulls or more correctly signal reductions.
As I raised the target (actually had to use a bigger one to see the response) the 4 positive responses became 2, and there was a reduction zone between them.
When the target height was about the same as the width of the TX coil, the 2 positive responses melded together and became one broad response.

I now understand now why a small surface target gives 2 responses and when it's on the digout pile almost impossible to find using usual techniques, given the 4 responses at very close quarters.

Another surprise was the almost 3/4 volt pk-pk ripple that rang on for parts of 10uS. At first I thought I needed to install damping resistors, but then remembered Zed's pic showing them installed within the coil. This may explain why my coil is so noisy, I could hardly use it in General timing because of the racket, I should've sent it back to Minelab, if I'd seen this I would've.
So is this intentional? Surely not, did some poor Malaysian lackey learn that day their son was hooked on heroin, or did she learn her husband was banging another, was she so out of sorts that she tested it and said to herself "she'll be right", or was the Boss standing over them with a stick, "you must deliver so many by 8 o'clock tonight or your pay will be slashed"
I know what goes on in some of these countries, i just hope Minelab chose a reputable employer!

If I used 2 targets, one on each RX coil and in varing positions, I wasn't able to reduce the signal completely as you'd expect in an opposing configuration. So it really does appear to be adding, but I assume with the rotation of the RX coils relative to the TX one, as in the case with a simple DD configuration.

Here's an image that roughly depicts the responses (makes me think of bernte_one for some reason :-) )
And the flyback ringing.

[6666]

Hi Kev, I am ok thanks, just sometimes you get in the zone and time just flies by and the nights gone,
thanks for tests, we are at the mercy of the factory testers and how accurate they are in manufacture.

[alimosavi575]

god

[Kev]

Welcome to the forum alimosavi575. I imagine Persia must contain some amazing treasures being located in the cradle of civilisation.

Been doing a bit on the shell buck while waiting for parts to arrive.
All I had in my scrap corner was MDF, so not sure how durable it will be to hot plastic being drawn over it.
I intend to give it a good coat of epoxy and then wax it before use, hopefully it will give a few shells before disintegrating?
I've made the ears removable, so they can be used on different shell sizes.

I intend using some 1.5mm HIPs (High Impact Polystyrene) which is way cheaper than ABS, but quite flexible.
That's the reason for the quite thick ribbing under the ears, I might reinforce this with carbon fiber or similar.

I wish I had a small CNC machine it would make things a lot easier, juggling a Dremel in a mini drillpress is better than nothing I suppose.

Cheers
Kev

[6666]

nice work

[IBGold]

Hi Kev,

I use MDF and it is fine I just fine sand it and give it a dust of talk powder and form but I use 1.0 ABS and 1.5 ABS works fine for me also have used chipboard with out any bad effects.

Regards, Ian.

[Kev]

Hi Kev,

I use MDF and it is fine I just fine sand it and give it a dust of talk powder and form but I use 1.0 ABS and 1.5 ABS works fine for me also have used chipboard with out any bad effects.

Regards, Ian.

Thanks Ian for taking the time and sharing your confirmation, it's nice to know my work probably isn't in vain.

I bought some HIPs sheets to make some skid plates and realised that it would probably thermoform nicely.
It's just not as rigid as ABS, but it appears to be more scratch resistant, a little more like polycarbonate, plus and a big plus locally it is a quarter of the price of ABS.
So with a little strengthening and ribbing it should do the job nicely, I'll share my results here.

Cheers
Kev.