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Thanks Silverdog !
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Silverdog, I left you messges here on geotech. Did you see them ?Comment
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Hi Silverdog,
I had ordered two SURF_PI PCB's and both were populated with components from the local market with optimum results. The quality was superb.
I would like to receive boards for IDX and VDI project as well. Is possible to place an order now?, or tell me by when?
regards
VasileiosComment
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IDX boards will be 7-10 daysComment
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VDI question
Does anybody know why the MCP602 was chosen for the VDI ..
Can I use the LF347 OpAmp instead ?
I aim to work on VDI on the Atmega chip,
after I get the IDX Board functional.
At the moment my Idx board only works at a range of 3 inches for a coin,
while being unstable sweeping the coin on the floor.Comment
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Instead you can use the MCP602 TL072Comment
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unless i'm mistaken he no longer sells vdi kits.Originally posted by vasileios View Post
you have to make those yourself.Comment
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While I am waiting for the IDX Kits,
I wanted to do some testing witrh Coil Sizes.
Via calculations, can I say that the following Coils are correct ? :
From:
27cm Coil , TX , 0.7mm Wire , 35 Turns
27cm Coil , RX , 0.2mm Wire , 160 Turns
To:
13.5cm Coil , TX , 0.7mm Wire , 52 Turns
13.5cm Coil , RX , 0.2mm Wire , 235 Turns
21cm Coil , TX , 0.7mm Wire , 40 Turns
21cm Coil , RX , 0.2mm Wire , 185 Turns
41cm Coil , TX , 0.7mm Wire , 28 Turns
41cm Coil , RX , 0.2mm Wire , 128 Turns
Note, that these are the Calculations for the Total Size of 2 Half/Semi-Circle Coils.Comment
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If you can get a 9" shell this is about the right scale for this machine for coins etc.
The signals are too wishy washy with large coils on small targets.
Its not by chance that most commercial units have 8~9" coils.
,
If you aim is a frquency, The absolute L value is not of much interest., as you tune it with a capacitor.
The absolute frequency is of no interest to me. People say I need example.. 6583Hz - do you really, of course you dont. Sure your aiming for 6.5K - if it was 6900Hz , no drama use that
I f your Rx was trying to be 5000Hz, and you think you have 4800 - just use that.
If you were aiming for 5000Hz and you got 1000Hz or 25000Hz, sure you got it wrong redo it right. SComment
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Well, i wanted to do some testing, to compare Coil Sizes,
do some research experimenting.
I have discovered some tricks in past metaL detector projects,
and I wanted to test them here too.
I am interested in testing and comparing Shapes and Sizes between Coils.
I also wanted to add to projects and info to the Arduino example,
when I get the IDX up working correctly.Comment
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This works very well with my unmodified setup. Touch under 40cm on my setup same for iron clad and copper 2p. Very reliable signal to 37 to an occasional beep if you get the speed and directly over the center at 40cm. Not as deep in real ground.Originally posted by ampirate View Post
27DD TX wire from 0.70 to 35 laps
27DD RX wire from 0.15 to 270 lapsComment
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I've been making lots of coils lately too. How did you calculate these for a D shape? Most use a circle for calcs;
"Via calculations, can I say that the following Coils are correct ? :
From:
27cm Coil , TX , 0.7mm Wire , 35 Turns
27cm Coil , RX , 0.2mm Wire , 160 Turns
To:
13.5cm Coil , TX , 0.7mm Wire , 52 Turns
13.5cm Coil , RX , 0.2mm Wire , 235 Turns
21cm Coil , TX , 0.7mm Wire , 40 Turns
21cm Coil , RX , 0.2mm Wire , 185 Turns
41cm Coil , TX , 0.7mm Wire , 28 Turns
41cm Coil , RX , 0.2mm Wire , 128 Turns"
I got some 9" shells from this site;
https://sites.google.com/site/dbcoil...10-inch-shells
He has 9" and 10" and covers to fit too. I think it was $15 for a coil and cover plus shipping.
Also ************
"If you aim is a frquency, The absolute L value is not of much interest., as you tune it with a capacitor.
The absolute frequency is of no interest to me. People say I need example.. 6583Hz - do you really,
of course you dont. Sure your aiming for 6.5K - if it was 6900Hz , no drama use that
I f your Rx was trying to be 5000Hz, and you think you have 4800 - just use that.
If you were aiming for 5000Hz and you got 1000Hz or 25000Hz, sure you got it wrong redo it right.
What are we aiming for? Ivonc made some similar comments and it is unclear if we need just a certain number
of windings and tune from there or what. I know the inductance changes day to day and the caps aren't exactly
the value they say they are. So is the best we can do is count windings and use the right diameter wire?Comment
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For non-circular coils, find the area enclosed by the coil (one way is to draw it full size on graph paper and count the squares). Then calculate the size of the circular coil that encloses the same area, and find its inductance. I've found, from measurement, that gives good results.Comment
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Im saying dont beat yourselves up using umpteen decimal places, close is good.
With the IDX, I made the Tx 12kHx and the phase shifters for clocking the Disc and GEB channels worked well. I had the Rx tank about 8kHz.
As long as the Rx is about 75% of the Tx you will have some sensitivity. If you have staggering Air sens - it is likely the Rx taank is tuned too close to the Tx. And will be twitchy over land.
I think quiazhis coil cal app works well enough and is well regarded and proven so will give good first time results. People often make lots of versions and say oh that one was bad so I made another... There is no bad coils, its just how you phase them up and tune the phasing for ferrite reject, good sens, average null at preamp out.
If you have dry sand or clear earth low mineral, you can move the ~Rx tune colser to Tx and will give extra depth without the twitchy.
If you have meadow or wet minelaised clay you will benefit from having the Tx / Rx split up a bit more. Reduces sens a bit, but wont false about..
These are the trade offs I work to.Comment
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