IDX-PRO+VDI

[hoadlies]

HI TO ALL ..Barry here from OZ, KOALA ,I am afraid I need to go back to the Drawing board on the China unit that I made a DD coil for it seemed to air test fair,, but not good in practice ..BUT not now I will have another go later down the track ..

STEVE ,,,The IDX is Great found a few bits of wire 22 shell-case alloy pop-rivett drilled-out bits [look like washers] etc,,,great on coins!!!! but only in my back yard !!! [Need to get out bush with it soon] ITS very quiet on my Red clay ground ,Better than my NEW whites GMT Also it has better steel rejection than the whites ..
The whites once getting the ground OK is better on small lead shot [I have no gold-nugget to test with ] very very sensitive..

WELL i am getting ready for a trip to Victoria [Gold-Fields] for 2-3 weeks Health permitting [been a bit crook] we will be off in 3 weeks ..

I hope to report some good finds of something ..??????????????????????

HAVE a great time out waving fella's ,,CHEERS,,,,,,,,,,,BARRY..

[golfnut]

You need a 7808 not a 7908

[golfnut]

If you got 1kHz it sounds like you used the Rx coil and the 1uF for the Tx oscillator!!

[Koala]

And RX 33nF not 3.3nF.

33nf

[akasyto]

And RX 33nF not 3.3nF.

[Koala]

Could someone please check my numbers for me. I'm about to build my first coil for my IDX. I want a coplanar first and have used various internet calculators but I just want to be sure as I don't want to waste the copper. Here's what I've come up with (this is for a 30cm coil)...

TX 587μH 30cm diameter 32 turns of 13AWG plus 15cm 8 turns 13AWG bucking coil 1μF cap
RX 35.6mH 15cm diameter 337 turns of 38AWG 3.3nF cap

Thanks, and this forum has been great for info for my build

use this data known to work very well

http://www.geotech1.com/forums/showthread.php?20315-Concentric-coil-for-IDX&highlight=Idx+ccoil

[Alphabetix]

Could someone please check my numbers for me. I'm about to build my first coil for my IDX. I want a coplanar first and have used various internet calculators but I just want to be sure as I don't want to waste the copper. Here's what I've come up with (this is for a 30cm coil)...

TX 587μH 30cm diameter 32 turns of 13AWG plus 15cm 8 turns 13AWG bucking coil 1μF cap
RX 35.6mH 15cm diameter 337 turns of 38AWG 3.3nF cap

Thanks, and this forum has been great for info for my build

[akasyto]

Actually, I pulled the 7908 - and just shorted In to Out.I wanted to try with a 9V Bat first.
to reduce chance of burning anything out. I read about 7.2V as actual Vsupply with V-Meter.

But I am only reading 0.2V pp on the TX Pins anyway.
The Wave is Bursts at about 600Hz-1khz.

7908?

[Koala]

Ok, on Oscilliscope, i have about 5V pp at about 1khz, with Coils.

- I need to find the caps : 1mf and 0.033mf ?

Yes

1MFD TX and
33 nF RX

Use good quality otherwise they will drift in use

They are part of the oscillator circuit so without them you will not be able to measure the TX peak to peak.

[ampirate]

Ok, on Oscilliscope, i have about 5V pp at about 1khz, with Coils.

- I need to find the caps : 1mf and 0.033mf ?

[golfnut]

to get 16volts pp you need a resonant coil cap combo. When the coil cap is connected it can function as a Tx.


Then you will have a Tx to measure

[ampirate]

I am using an oscilliscope.
But I have not attached the Coils yet.

I did discover that the Battery was low, and had better and louder results with a new 9V battery.
I dont have time at the moment to finish testing - with Oscilliscope and Coils - will do later.

[Koala]

Ok,
Oscilliscope showed about 0.2V pp (yes 0.2V and not 16.0V !) at about 600hz-1000hz.

I did tap downs of the ic components,
and now I get a random squeaky sounds as I touch or wave my fingers around the TX leads.

But the volume Pot does not work, and the audio is only a whisper.
I am using a small 50ohm speaker 1/2W (could not find 32ohm) - should be close enough.

Using 9v Bat - shorted over 7808 reg - so getting about 8v.

What size capacitor did you add across the TX winding?

Are you measuring with the oscilloscope as a meter does not work well

[ampirate]

Actually, I pulled the 7908 - and just shorted In to Out.I wanted to try with a 9V Bat first.
to reduce chance of burning anything out. I read about 7.2V as actual Vsupply with V-Meter.

But I am only reading 0.2V pp on the TX Pins anyway.
The Wave is Bursts at about 600Hz-1khz.

[golfnut]

first things first you need a 12v battery.

This is your ext goal, you may have blown the 8 vol t reg putting 9v on its output.

put 12 in as the design and measure the 8V out