hello xavier ,
now it's been "thinned down" and "basic -ified" (new word) it's time to build on it and add more features .
and yes , the last schematic is a working one .
hello 6666 ,
detection of various metals depends on where you have set your delay / sample point and width ,
larger width = more ability to charge and discharge to holding cap resulting in a quicker responce ,
have a look back at the pic i posted earlier regarding the curve responce to various metals ,
have set mine to the middle of the decay at the moment with a 20us sample window good for all metals ,
set at the start of the slope to be more sensitive for gold and brass ,
set at the end for steel and iron ,
have tried sample at the start of the slope with a narrow sample time of 10 us , responds to gold / brass very well and lessens the responce to iron and steel.
with max pulse and min freq ,20us sample in the middle , can detect our lasses gold ring at about 25 to 30 cm
i have now done away with the freq adjust pot and fixed it at 200hz , as it didn't make much differance ,only to battery life.
volume , threshold coarce and fine is all you need i think.
as i said before would be nice to have a switch , poss 3 position to switch in 3 presets for delay / sample , start /middle and end of curve. then by listening to the respone of a target poss work out what it is , only problem is threshold would have to be adjusted every time it's altered.
oh well.
Posted on: August 13, 2011, 11:04:55 AM
UPDATE:
just purchased an inductance meter and tested my coil ,
25 turn , 30cm dia bundled , no shield , 0.6mm wire with 0.3mm pvc covering , 1m of "mini8"coax attatched.
online calculator said it would be 380uH or there abouts ,
just measured it 527uH , nearly laughed my ar*e off !!!!
does this sound about right
or is meter poss a LITTLE incorrect
if it is 527uH , wouldnt that be to slow on a PI to respond well to gold
i'm confused ,,,,,hell boy ,,,,,,we all cunfused.
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