IDX-PRO+VDI

[gtdavid]

Ok I have started to calculate the resonate capasitor for my coils and by the calc it says that a 1u on tx will resonate at 5.024 khz and the sound card scope says 5.05 khz so I think that the sound card scope is not far off .
Now I have 600n worth of caps on the tx and now I have 6.45 khz tx.
Proformance has increased by about 5cm.
Now my question is what should I shoot for on the rx that is the ratio with tx at 6.45 khz.
Thanks I am learning a lot from these forums.

[gtdavid]

hay i am now at 40 cm with a 23mm coin while rejecting iron.
6.80 khz tx / 27 v p-p
33.3n on rx (10.42 khz) / 407.9mv
should i bring rx down as i am getting annoying beeps / chatter coming threw ..

[Davor]

IMHO - no. A good device is always a bit "nervous". It will not be a problem, and chatters will vanish when you go out of your lab and civilisation, so keep it this way.

[Koala]

hay i am now at 40 cm with a 23mm coin while rejecting iron.
6.80 khz tx / 27 v p-p
33.3n on rx (10.42 khz) / 407.9mv
should i bring rx down as i am getting annoying beeps / chatter coming threw ..

23cm to 40cm very well done. Is that just the tuning of the capacitors? Are you still running at 12 volts and have you tried going back to 8v. I think that's about as good as you can expect and still be useable. I am at 35cm with a home made DD coil when I make my next it will be better. I was also at 40 cm at one point but left a probe near the coil while nulling tried to correct with a piece of graphite but can not get back to my best distance.

[gtdavid]

Yes I am now running 12v .
All I have done is tune with caps on tx and rx.
I will test with 8v later and post results and cap values.
I may also test with 20v.
Just need to look up the max input of my reg.
Is it possible to increase the amps to the tx circuit? ?
This is some thing I would also like to test..
All my tests are done with the speaker only I will get some headphones today and see how we go.
My alu boxes are on there way and my nice new alu pot knobs are also I will post pics of end machine soon.
I am also going to play around with some chip upgrades .. I will post resilts.

Just want to say a big thanks to the members of this forum . You rock! (Hopefully not hot rock lol).

[golfnut]

Your 35cm wont be realisable in the soil - so its not a problem.

If you get a depth in soil the same as your coil diameter your doing real well with these sort of machines.

David your at approx 7k and 10k my one is similar but My Rx is on low side injection - I currently have 8kHz Rx and 11.6kHx Tx


Getting you ground balance set real low, and keeping it low - in use, is your next challenge well done so far


I wanted 24v but I think mine went twitchy its use- sure there was more Tx current in the tank - but I couldnt use it gainfully in my soil. I cant remember in truth.

I run at 12 by default, with a switch to bring in 8volts extra - tiny improvement only - I use 12volts all the time.

The reg can take 24v easily

S

[gtdavid]

Yea I know I wont get the air depth in the soil but I figured it was a good place to start.
Did you get any improvement or extra stability with having a high tx and low rx?

[ossamaussama]

how to tune dd coil without scope?

[Davor]

You need a real AC millivoltmeter instead, or a PC scope. Trouble with millivoltmeters at AC reading is that they tend to lose sensitivity at frequencies higher than 100Hz, and you usually learn about that problem the harder way.

[gtdavid]

Pc scopes are easy to setup and are usually free just make shore that you make up a voltage divider probley about 50 to 1 to protect your pc

[ossamaussama]

ok i tried to measure ac voltage at pin 6 of u1

i get the max sensitivity if tuning the coils until i get 1 volts ac not zero
is that normal ?
or should i measure the ac voltage across the coil before the amplification stage?

[gtdavid]

ok just swapped out the ne5534 for a opa627 and there is a drop in noise same detection depth but target beep is more noticeable as less noise.
happy with the change thus far.

[gtdavid]

Can someone please give me a black and white 2 tones layout
Please

[gtdavid]

my 2 tone board does not work and i have to turn my sensitivity to 0 to get it to detect anything..
otherwise i get constant beeping.
what could cause this would it be because i am using a fisher cz coil?

[ossamaussama]

why i hear sound when the coil move ?