Capacitive Force Sensor
Explore the original four-stage model from plate motion to ADC and vibration intensity. Percentages and physical values are illustrative.
Variable-gap capacitive force sensor
Horizontal plate motion → changing gap → STM32 ADC → PWM fingertip cue
EDUCATIONAL BENCH SIMULATION
50%
1. Force changes the gap
The plates face each other. One plate moves horizontally toward the fixed plate.
d = 25%
FORCE →
moving / sense
fixed / ground
Normalized plate gap
25%
2. Gap changes capacitance
Plate area stays constant; the distance d changes.
C = εA / d
Relative capacitance
1.78 × C₀
Sampled RC voltage
1.49 V
Smaller gap → higher C → slower charge
3. STM32 processing
The ADC reads the RC voltage and calibration estimates pressure.
STM32F303K8
12-bit ADC reading
1850 / 4095
Calibrated pressure estimate
50%
4. PWM creates the cue
The STM32 changes PWM duty cycle to control vibration intensity.
3 V coin motor on the surgeon's finger
PWM duty cycle
50%
Pressure 50% → gap d 25% → capacitance 1.78× → ADC 1850 → PWM 50%