IDX-PRO+VDI

[bernte_one]

at moment i use the PeakTech 2010
before my 4070l from china falls down to is single parts
the PeakTech 2010 seems to be very accurate it is fuly produced here in germany the price is unbeaten
delivered together with good test pins, some adapters and cover
maybe its an option

[Tepco]

Typical problem with similar instruments and air coils. Reason for this is very small value of reference capacitor used to resonate measured L, only around 1nF or so. This is OK for large inductances made on some core or ferrite, but air coils have large turn numbers and larger inter winding capacitance added to reference one, producing larger freq. shift and wrong L value calculation, can be routinely 10 or 30% off, even more. I allays check exact coil tuning with oscilloscope and generator. Naturally, true fixed frequency RLC bridge can fix this, but not for 37$.

[dfbowers]

Apparently you are using some sort of resonant LC meter (similar to mine) but this type of instrument can introduce significant errors when used to measure large inductance coils (RX coil) due to large coil self capacitance and variable frequency used for L calculation. Try to verify coil inductance by other means using different method or instrument, RX may be slightly detuned.

I tried building an Arduino inductance meter featured on youtube. Like you said the lower inductances measured close, but not the larger inductances. My Rx coil was measuring 50mH, when I knew that it was only 35mH.

[eduardo1979]

Nice work Eduardo! BTW.. I did try to adapt my Arduino project to the IDX without success. The problem is that the TGSL is a noisy beast compared to the IDX.
The later stages of the TGSL, before the LM393's are very noisy as compared to the IDX, and the VDI numbers just would not settle down - at least that has been my experience.
Maybe an additional stage with different filtering to the VDI would do the trick.
I once tried to increase the frequency of the IDX to 15k as well. I got it to work, but the IDX became noisy in the later stages just like the the TGSL.

I think with a thing like that would solve the problem.

[Tepco]

Apparently you are using some sort of resonant LC meter (similar to mine) but this type of instrument can introduce significant errors when used to measure large inductance coils (RX coil) due to large coil self capacitance and variable frequency used for L calculation. Try to verify coil inductance by other means using different method or instrument, RX may be slightly detuned.

[gustavodigitales]

for the records.

http://dx.com/p/lc100-a-2-5-lcd-digital-high-precision-inductance-capacitance-l-c-meter-148475

very cheap lc meter for only 37 bucks...

[gustavodigitales]

Sorry is 360t 36.5 mH 12 cm diameter 0.20 wire
here is my measurements for both coils .
i`m very confused why not........
other thing now i`m using a usb cable 4 conductors plus full shield.
i gonna try changing the 4066 ic.

[dfbowers]

Gustavodigitales,
Something is not right with your RX coil, Your number of turns seem way off. If you use the coil calulator in the forum, it shows that for a 35mH coil it should be almost 450 turns. That's assuming that your RX coil has a 44mm radius. 260t might be about right for a 27CM DD coil.

Don

[dfbowers]

Gustavodigitales,
Hmm, nice effort there. I really would like to see your project come together. I have the luxury of matching everything to a White's BM600 coil so I just made resonance the same for my project and the White's manufactured coil.

Now, if I'm not mistaken, 35mH together with 33nF = 4.68 kHz using this calculator:

http://www.whatcircuits.com/lc-resonance-frequency-calculator/

That's why I was questioning the specs posted elsewhere. The coil is pretty picky as to how it's tuned.
Do you at least have access to a White's coil for reference? We need to cut your problem in 1/2.

[dfbowers]

Nice work Eduardo! BTW.. I did try to adapt my Arduino project to the IDX without success. The problem is that the TGSL is a noisy beast compared to the IDX.
The later stages of the TGSL, before the LM393's are very noisy as compared to the IDX, and the VDI numbers just would not settle down - at least that has been my experience.
Maybe an additional stage with different filtering to the VDI would do the trick.
I once tried to increase the frequency of the IDX to 15k as well. I got it to work, but the IDX became noisy in the later stages just like the the TGSL.

[gustavodigitales]

I`m still no luck there.
tryed with concentric coil tuned tx at 6.54 KHz 24 cm 0.70 mm about 33t rx about 260t 0.20 33nf at 4.6 KHz and bucking is 10t 0.70 direct over rx coil.
putting a 22nf cap in rx increases a lot residual tx and made the coil imposible to null below 8mv but increases 3 cm target distance.
i tried increasing rx preamp gain whitout success.
1 e coin at 24 cm in air.

[dfbowers]

Best bet is to get a kit from Silverdog. You cannot beat the price or convenience. Coils are very common and if you are building your first IDX you will dramatically improve your chances of being successful if you just buy a coil. Make coil building your second undertaking! Most importantly, read the entire IDX thread before you undertake the project.
Lots of help here too!

Don't know about a nugget detector,
Good luck..
Don

http://www.silverdog.co.uk/

[zipzip]

hi every body
i m just a new here and i found this idx project very briant and if its possible can have details on building one like it
i m also interested about small gold nuget detectors if its possible in a homemade edition lol thanx

[ApBerg]

Hello Don,

Thanks for the info !!

Best regards.

Ap

[dfbowers]

Coil update:
I finally got a chance to get out with this coil today. Without a doubt, best coil I ever made! Air tests were not that impressive, but it ends there. I have 3 lead balls (.570" diameter) buried in my test garden @ 7", 8" and 9". Doesn't seem like much, but in MY soil, ALL my detectors struggle to find any of them. My Shadow X5 is ablsolutely quiet. This coil with Silverdogs IDX kit hits all of them loud and clear in DISC mode and is more stable and deeper than my 9" and 10" homebuilt DD coils.. Ha! there is really something to be said about smaller coils. Again, this is only a 7.5" coil inside an 8" shell. (My TGSL MIGHT hit the first one on a good day with a 10" DD coil). Now, with that said, this is all old technology.. but exciting for a home hobby builder.

Also, I found an absolutely great source of graphite spray, which I used to finish my paper shields. Under $5.00 at you local Home depot in the U.S. Now, as I have read in other threads in the forum, some warn that covering large areas with graphite spray can spoil the null of your coil. I found this to be true, but insignificant.. maybe a 25% increase in the null voltage.

Don