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Here is the complete circuit diagram of the SPI-MX 3b
I will be posting the source code next week.
Dual phase pulses:
All the mosfets are used to switch the coil in both directions. If there is a better way let everyone know !
This helps to cancel noise;
External signals will shorten (or lower) half the target pulses, and lengthen (or increase) the other half.. thus the average will not be affected.
i.e Noise or emf will induce a voltage on the coil, the affect on pulses in one phase is the opposite on pulses of the other phase.
Conductivity.
The conductivity is calculated by comparing the long response with the short response.
i.e Working out the shape of the discharge curve.
This is accurate enough to tell the difference between a bottle cap and a $1 aus coin at any detectable depth %100 of the time
It can't however tell the difference between a vertical tent peg and a $2 aus coin for example.
The sound-scape or audio can be explored refined or changed in code.
Currently I use two tones.. one constant, and one according to conductivity.
This is because it is easier for the ear to compare two tones than to recognize a single tone with nothing to compare it with.
Having two tones enables fairly accurate target discrimination,..but I am sure there are other possibilities.
The two guiding rules of the SPIMX design are:
PERFORMANCE
SIMPLICITY
These are different requirements that sometimes conflict and sometimes compliment
Currently
There are no knobs to adjust, other than volume.
There is no display to look at, all information is available in the sound..through the ears, which are quite sophisticated and under-utilized instruments.
Tec
I will be posting the source code next week.
Dual phase pulses:
All the mosfets are used to switch the coil in both directions. If there is a better way let everyone know !
This helps to cancel noise;
External signals will shorten (or lower) half the target pulses, and lengthen (or increase) the other half.. thus the average will not be affected.
i.e Noise or emf will induce a voltage on the coil, the affect on pulses in one phase is the opposite on pulses of the other phase.
Conductivity.
The conductivity is calculated by comparing the long response with the short response.
i.e Working out the shape of the discharge curve.
This is accurate enough to tell the difference between a bottle cap and a $1 aus coin at any detectable depth %100 of the time
It can't however tell the difference between a vertical tent peg and a $2 aus coin for example.
The sound-scape or audio can be explored refined or changed in code.
Currently I use two tones.. one constant, and one according to conductivity.
This is because it is easier for the ear to compare two tones than to recognize a single tone with nothing to compare it with.
Having two tones enables fairly accurate target discrimination,..but I am sure there are other possibilities.
The two guiding rules of the SPIMX design are:
PERFORMANCE
SIMPLICITY
These are different requirements that sometimes conflict and sometimes compliment
Currently
There are no knobs to adjust, other than volume.
There is no display to look at, all information is available in the sound..through the ears, which are quite sophisticated and under-utilized instruments.
Tec
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