I replaced the volume pot in my Technics SA-206 with a ALPS 4-Gang Motorized pot. The motor is controlled by a L298n board connected to an ESP32. My question is: is it possible to somehow convey the current position of the pot to the ESP, (e.g. voltage) without incurring introducing a bunch of digital noise into the signal?
so wiper connected to pot, one pin connected to 5v and one pin connected to ground? Can I feed the pot with 5v and ground from ESP or is it better for it to have its own power supply?
so wiper connected to pot, one pin connected to 5v and one pin connected to ground? Can I feed the pot with 5v and ground from ESP or is it better for it to have its own power supply?
Doubt it - a volume pot will be log-law, you need a linear-law pot for position feedback. Unless you have a 4-gang pot with some log and some linear taper... Digital noise is removed by low pass filtering the pot with a capacitor.
Method 1
It is possible to obtain the position of the shaft using a small magnet (glued to the shaft) and a couple of linear hall effect sensors (say SS49) kept at 90* to each other. As the shaft is rotated, its angle / position is obtained from the two sensor outputs using a simple analogue arithmetic operation:
Vangle = abs(V1) - abs(V2).
abs(.) is equivalent to full-wave rectification and maybe achieved using an opamp.
V1 = blue, V2 = red, Vangle = black in the graph below.
However, since the angle voltage peaks at 90*, it needs to be counted 4 times to obtain 360* (full circle) rotation. Alternatively, a gear with a 4:1 ratio or could be used between the shaft and magnet to allow the output to be used directly.
Method 2
Connect the shaft to another linear pot and use its output for position feedback.
It is possible to obtain the position of the shaft using a small magnet (glued to the shaft) and a couple of linear hall effect sensors (say SS49) kept at 90* to each other. As the shaft is rotated, its angle / position is obtained from the two sensor outputs using a simple analogue arithmetic operation:
Vangle = abs(V1) - abs(V2).
abs(.) is equivalent to full-wave rectification and maybe achieved using an opamp.
V1 = blue, V2 = red, Vangle = black in the graph below.
However, since the angle voltage peaks at 90*, it needs to be counted 4 times to obtain 360* (full circle) rotation. Alternatively, a gear with a 4:1 ratio or could be used between the shaft and magnet to allow the output to be used directly.
Method 2
Connect the shaft to another linear pot and use its output for position feedback.
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I don't have the clearance for hall effect sensors nor a secondary pot on the shaft. I'm new at designing circuits, what low-pass filter setup would I need to filter out the noise coming from a 3.3V supply?
The sensors are small (BJT sized) and if needed, could be easily hidden under the knob on the front panel. Do you have a photograph of the situation ?
How do I connect the linear pot to the volume pot? Do I hook up ground, voltage and wiper between the two? Connect just the wiper?