Contraction & Heartbeat Overview

Dual ESP32 belts · last 12 intervals · adjustable thresholds

Belt A Waiting for IP
FSR: -- · BPM: --
WiFi: -- · IP: --
Force: -- N · Contact Δ: --%
Contraction idx: --
Belt B Waiting for IP
FSR: -- · BPM: --
WiFi: -- · IP: --
Force: -- N · Contact Δ: --%
Contraction idx: --
Last update: —
Model 1: FSR → Force R = A · F^{-b}

Non-linear FSR model (Interlink/Ohmite). Force F = (R/A)^(-1/b).

FSR raw A/B:-- / --
Force A/B (N):-- / --
Model 2: Dynamic Pressure P = k·F, dP/dt

Derivatives mark contraction onset/end using thresholds on dP/dt.

P A/B (arb):-- / --
dP/dt A/B:-- / --
Model 3: Smooth + Peak Filter → avg → peak

Low-pass + sliding window to estimate TOCO-like intensity.

Smoothed A/B (N):-- / --
Intensity A/B:-- / --
Contraction ↔ fetal heart rate linkage (Sletten et al., Acta Obstet Gynecol Scand 2016)

Study on 12 pregnant subjects showed graded fetal HR rise with uterine activity: moderate contractions ≈ +4 bpm, strong ≈ +5.7–7.6 bpm (Holter + electrohysterography, daily living). Hypothesis for this belt: FSR-derived force F(t) → normalized intensity I=clip(F/Fref,0,2) → ΔFHR=clip(4·I,0,8) bpm; predicted fetal HR = baseline + ΔFHR. Reference: Sletten et al. 2016 (PubMed).

Sensor Streams

Live inputs from both belts with thresholds ready to tune

FSR Sensor 1 · upper left

Contraction pressure (AU) · custom baseline

32

AU

FSR Sensor 2 · upper right

Contraction symmetry check

28

AU

FSR Sensor 3 · lower left

Deep pressure anchoring

30

AU

FSR Sensor 4 · lower right

Peak contraction capture

26

AU

Fetal heartbeat · Belt A

Optical/ECG probe on segment A

147

BPM

Fetal heartbeat · Belt B

Redundant probe on segment B

142

BPM

MPU6050 posture

Tilt/roll average · last 10s

3.2

deg

Alerts & thresholds

Custom alarms armed (heart + contractions)

2

active