Experimental Sub-sonic Rumble Circuit

[jonovid]

Hall sensor and a VCO at the end of a 10 Meter long telephone wire.
for the detection of subsonic frequency's of moving trains and earthquakes.
part of my own experimental design using parts that I have at hand.
most are AliEx. the npn transistor is an odd unknown type .
the first casualty was this dead circuit when moved over from the breadboard when it was working .
I then re-made a second circuit that is tunable.
been trying to add operating range to both the Hall sensor and the octave range of the 555 as a VCO.
circuit is temperamental & must be tuned at its threshold.   as a 8 up 20 to output at 5 V regulated power supply is next to be add to the circuit
the 5 vlot bus is because of the Hall sensor.  the 555 output will power a low-pass filter
so 555 square wave at 1khz can becomes a sine wave modulated by the Hall sensor.
modulation circuit is near DC so no capacitors are used.
 the head unit and the phantom power supply are not yet made.  frequency demodulation circuit.
the mechanical part of the unit is somewhat easy.   lead fishing weights recast.

  uses-
train photography trigger - earthquake sensor


 only part of the project shown here.