IDX-PRO+VDI

[golfnut]

hello, having finished my idx, here some photographs of my detector. it is thus the initial version without the multi mode tons and without the bill-poster and with a head D 27 CM house doubles.

Classy - with a bit of Buck Rogers!

S

[reiv]

Nice one ashefr10

golfnut: Your method of ground balancing works very well outdoor

I tried to increase resistances in filters of Geb and Disc channel:

I think I get 1.5-2cm extra, and now is more sensitive to small object, everything works ok, he is stable as before.

[golfnut]

Nice one ashefr10

golfnut: Your method of ground balancing works very well outdoor

I tried to increase resistances in filters of Geb and Disc channel:
[ATTACH]25503[/ATTACH]
I think I get 1.5-2cm extra, and now is more sensitive to small object, everything works ok, he is stable as before.

Good news on the higher gain filter/amps - one potential drawback would be recovery time following saturation following a large taget.

I have increased the front end gain on mine as a test but it got too chattery, Id say how it is is optimal.


I may try the extra gain in the IF as you did. If you can get 75% of your coil diameter on a small coin in soil, your doing really well.


S

[reiv]

My friend who build idx too, has made one more interesting mod. He moves threshold from U5 to U6, like in tesoro schematics. He said that now threshold works better-better for eliminating chattering with no cutting volume in the same time... Something like this:

He also had a switch to cut off PP channel while using dscr. as You did. What do You think about this?

[golfnut]

This pot on mine I use as a volume control really.

In the drawing of your friends work Id imagine the pot will have less range or effect as it eliminated the dc gain of U5.



I have been experimenting as ever and testing on testbed. I feel ashamed to say it but Ive always tended to have my GEB pot set near where ferrite is rejected. In use I get chatter here, so I always need threshold up a little.

Recently I have got better with it and have made changes to how I tweak it all.

There was a very quiet kind of dead zone up toward 9/10 which I have always avoided as I didnt beleive it was working properly up there..


Tweaking the geb range to 9/10 it is almost silent and Ive always thought not really working properly as so quiet.

With the Geb in this relatively new position I can drop the Threshold to essentially zero and reap more target sens.



7" is a breeze hovering 1" over the mown lawn - previously I have to touch the lawn for solid hit.

Finally got the 8" target everything maxed, so Geb finely set at about 9/10, sens max, thresh min, Disc just rejecting irom - needed coil centre sweet spot plus scuffing the lawn for two way tone.


Everthing had to be perfect for the 8" and I think I would have walked past it in the field.

Gets my 15mm dia silver at 6 1/2" easily.

8" has been a bit of a goal for this one as I used a good Explorer II and it did 8" flat out on the bed.

If this kit had auto Geb I think 8" would be its max using a 10" DD and be pretty usable.

S

[golfnut]

forgot

I also added a 100n plus a 1n to U4 pins 6/2 in attempt to smooth any noise on this reference.

My Tx volts was 12V for the last post.

S

[Aiko]

Hi Guys,

I just finished my IDX and it works but for now the detection depth is poor - about 20-25 cm for 1 euro coin.
The discrimination is good.

I have several questions:

1. Is it possible to achieve this working parameters with TX amplitude 1.2-1.5 V? I measured it with a brand new digital oscilloscope.
2. If I have 1.2V instead 16V amplitude, where I should search the problem?
3. Where I should measure the frequency of the RX?

Thank you in advance!

[reiv]

You have 1.2-1.5Vpp at Tx or 1.2-1.5V AC ?
If You have smaller voltage at Tx, try to focus on this part of circut (generator) :

To see what resonat frequency your Rx coil has, You should build simple generator like Collpits for example, it was write about it few pages earlier in this thread.

[Fabian]

Hello Friends. Am making coils for a IDX head with a CC mold I have. I got the TX coil parameters, but it still fails with the RX. I have the right inductance (34.9mH) correct resistance (a little high 144 Ohms) but I can not right the exact capacitance. The meter indicates -1.045 uF (minus) and the frequency is close to 0.27 kHz with a 33nF cap in parallel.

I tried to compensate with capacitors placed in parallel but I can not make it vary significantly. Did anyone notice what is my mistake?

Thank you in advance.

Fabian

[Aiko]

You have 1.2-1.5Vpp at Tx or 1.2-1.5V AC ?
If You have smaller voltage at Tx, try to focus on this part of circut (generator) :
[ATTACH]25545[/ATTACH]
To see what resonat frequency your Rx coil has, You should build simple generator like Collpits for example, it was write about it few pages earlier in this thread.

Hi reiv and thanks for the answer! It is 1.2-1.5Vpp. What is the correct value?

[reiv]

About x10 more Check your generator/voltage supply.

[golfnut]

Check your scope probe, is it a x10 !

S

[Aiko]

About x10 more Check your generator/voltage supply.

Of course - a stupid amateur mistake Now it is 15 V with the new TX coil 1 ohm. It seems that the resistance of the TX is very important for the TX voltage.

[reiv]

And what was wrong, scope probe ?

[Aiko]

And what was wrong, scope probe ?

Yes! By an mistake I quoted your post, but thanks to both of you. I was sure there is something stupid like this, because with 1,2 volts on the TX I would not have a working detector.