IDX-PRO+VDI

[ampirate]

Well, I discovered the problems,
- thanks partially to Koala.

The Coils needed to be Nulled-Out
otherwise no Sound.

Second, the Piezo did not work here either,
the replacement with a tiny cellphone Speaker gives a LOUD Buzz.

Now I need to adjust, Range is only 6-inches with Penny and Quarter and Brass Coin and Merc Silver Dime.
Thanks again.

[calebsone]

jlsillicon why does your cd4066 have that circle at the bottom is it wrong or am i seeing it wrong the way every ic i ever seen has that to mark pin one i relooked maybe im wrong. did you reuse any old parts or pull parts off an old piece of electronics equipment? no i think iam wrong all together look at the diode by the 347 it looks to be touching that resistor on the leads

[jlsilicon]

Yes, I will check that Diode.

As for the ICs, I marked all top indent tabs with whiteout - so I can see them clearly.
All seem to match the quick_connect_finalvdi.jpg diagram.

No used parts; these are from the Silverdog kit.

Will check,
thanks !

[jlsilicon]

Why are some of the DD-Coils not lined up straight, like the SEF DETECH Coil.
- This Coil is really 2 Ovals - not a True DD Coil.
Doesn't this reduce Sensitivity or Range ?

[golfnut]

No doesnt seem to. I have a Nel Hunter and depth is approx the smallest dimension.

If you machine is making a noise? You may have it stuck in Pin point mode. A test could be disc has no effect and iron is as loud as non ferrous.

If you think your stuck in PP you may have left the 100k resistor out which you mount vertically.


If none of my writing helps , are you running this from a mains power supply, do you have a flourescent lamp near it, TV, computer, anything powered.

Screens ok.

[jlsilicon]

Can you specify those dimensions approx ? :
- Coil width, Height, General Depth,
- Circular or Long Oval outer Coil shape ?
- smallest dimension of what ?

[ampirate]

Tonights Tests:

I readjusted the Coil to a general circle with proper Inductance 0.587mH , 35.6mh .
Coils have Caps.
Then adjusted Null to as lowest - about 12mV.

Adjusted :
* GEB to center,
* SENS to Clockwise,
* DISC to Ccw,
* THRESH to Ccw.

Measurement Ranges as follows:
* 4in Ferrite Rod -------------- 20cm
* 2in Foil --------------------- 5cm
* Nickel, Penny, Bronze Token - 15cm
* Quarter -------------------- 18cm
* Tin Can -------------------- 25cm

Currently has No Shields or Cable.
Board is right next to Coils - needs cable.

[golfnut]

looks as this one..

http://www.metaldetectorshop.co.uk/s...oduct_id=62071



generally depth is approx the coil diameter. On an appropriate target say coin 30mm dia.


So a 12" reound DD may get the coin in above eaxample.

An 12"x 8" ellispe would tend to go 8" on same target. Not 12" the larger dimension

[ampirate]

New Results after bending Coils some, and adjusting GEB :

* 2in Foil ----- 35cm
* 4in Ferite Rod -- 30cm
* 1in Copper Disc - 25cm
* Quarter -------- 20cm
* Nickel ---------- 15cm
* Penny ---------- 10cm

This is with the 24cm Coil.

Is there a way of increasing Range by adjusting the Pots ?

I currently have :
* SENS = almost CW max
* GEB = about 10 oclock
* DISC = CCW max
* THRES = CW max

[calebsone]

so i have started its going well the power supply is done so is the pre amp. now iam wondering can i use 1/8 watt resistors all the small foot print spots around the LF347 and the LM358 or does every thing need to be 1/4watt if so it would make it much easier

[Koala]

so i have started its going well the power supply is done so is the pre amp. now iam wondering can i use 1/8 watt resistors all the small foot print spots around the LF347 and the LM358 or does every thing need to be 1/4watt if so it would make it much easier

1/8 is fine. If I remember correctly less than 40ma draw

[golfnut]

New Results after bending Coils some, and adjusting GEB :

* 2in Foil ----- 35cm
* 4in Ferite Rod -- 30cm
* 1in Copper Disc - 25cm
* Quarter -------- 20cm
* Nickel ---------- 15cm
* Penny ---------- 10cm

This is with the 24cm Coil.

Is there a way of increasing Range by adjusting the Pots ?

I currently have :
* SENS = almost CW max
* GEB = about 10 oclock
* DISC = CCW max
* THRES = CW max

Snap 1/2" off the ferrite. Use that. Tweak the GEB pot so the ferrite just dissapears, then re do you target ranging.

Use a small clean iron also to assess your Disc out of iron, retry your ranges with iron rejected.


If you cant get rid oif the small ferrite your phasing is off. Leaked signal out of the preamp is a ways off wrt to Tx signal reference



You can lift sense slightly by moving the Rx resonance closer to the Tx.
Downside is can be more twitchy over the ground.


Could also reduce the resistor value on the divider network for the reference on the comparator. The DCref can be measured with a dmm a practical minimum is about +1mV this works in a no noise area with not too trashy soil.

Dont boost the preamp, it has plenty already and likely oscillate.
Raising the current in the Tx oscillator - the sense can go down, I think the extra Tx harmonics deafen the Rx and sych dets - unconformed
The filter amps after the synch dets have loads of gain already and again can oscillate if gain raised.

[onuba]

when coil wire is touched sounds what happens? thank you

[Koala]

when coil wire is touched sounds what happens? thank you

Shield not working properly. Without a working shield the faintest touch will sound. Coil will be unusable outside.

[ampirate]

Tonights Testing,

I found I get higher Range, if I shift off the Null Value slightly inward - probably bending coils added Inductance.

I hooked the X and Y to the Oscilliscope with Gnd of course.
The Angles I got from Y/X based Oscillator Mode - from Flat Left as 0deg - to flat Right 180deg :

* 50 Euro Cent - 10deg
* FOIL - 20deg
* Copper Penny - 45deg
* 2 Euro - bent leg 90deg to 180deg (2 metals)
* 10 cent Euro - 140deg
* 1/8in x 2in Threaded Iron Wire - 145deg
* 3in Ferrite - 145deg
* 5 cent / 2 cent euro - 150deg (Iron ?)
* Beer cap - 150deg
* Quarter - 150deg
* Merc Dime Silver - 160 deg
* 50 cent Euro - 170deg