Software for
work & play.

The Python model generates a reading every simulated second. A cycle heats to 62 °C, holds for 12 seconds, and cools to 40 °C. A reading of 76 °C or four seconds without a fresh reading trips the simulated cutoff. Reset requires acknowledgment and a fresh reading at or below 40 °C.

The three traces are embedded for offline playback. Acknowledgments and resets are recorded in the current replay.

Forecasts use 4,000 seeded synthetic reference runs and 1,200 independent validation runs. The generator samples normal cycles, heater faults and intermittent signal loss in a 50/30/20 mix with varied heating rates and fault durations. Each run contributes its first matching observation to a group. During a heater mismatch, grouping uses a 4 °C band, recent temperature slope, and whether the mismatch persisted for three samples. Stale samples group by elapsed time since the last good reading. The interval is a 95% Wilson interval for the reference group's trip rate. These percentages describe this simulated population.

"""Generate a repeatable thermal-cycle simulation, sampled once per simulated second."""

import json
import sys

SETPOINT = 62.0
TRIP_LIMIT = 76.0
RESET_LIMIT = 40.0
STALE_TIMEOUT = 4
SCENARIOS = ("normal", "heater", "signal")


def simulate(scenario, heat_rate=1.7, stuck_seconds=99, dropout_start=12, dropout_seconds=8):
    if scenario not in SCENARIOS:
        raise ValueError(f"Choose one of {', '.join(SCENARIOS)}")

    actual = measured = 24.0
    last_good = hold_started = 0
    state = "Idle"
    alarm = ""
    events = []
    samples = []

    def log(second, title, detail):
        events.append({"second": second, "title": title, "detail": detail})

    log(0, "Ready", "Temperature sample received at 24 °C.")
    for second in range(160):
        if second == 1:
            state = "Heating"
            log(second, "Cycle started", "Heating toward the 62 °C setpoint.")

        command = state == "Heating" or (state == "Holding" and actual < SETPOINT - 0.3)
        jammed = state == "Holding" and scenario == "heater" and second - hold_started <= stuck_seconds
        heater = command or jammed
        if heater:
            actual += heat_rate
        elif state in ("Cooling", "Tripped"):
            actual = max(24.0, actual - 1.45)
        elif state == "Holding":
            actual -= 0.27

        good = not (scenario == "signal" and dropout_start <= second < dropout_start + dropout_seconds)
        if good:
            last_good = second
            measured = round(actual, 1)
        if scenario == "signal" and second == dropout_start:
            log(second, "Signal lost", "The sensor stopped sending samples.")
        if scenario == "signal" and second == dropout_start + dropout_seconds:
            log(second, "Signal restored", "Fresh temperature samples are available.")

        sample_age = second - last_good
        if state in ("Heating", "Holding", "Cooling"):
            if sample_age >= STALE_TIMEOUT:
                alarm = "Sensor timeout"
            elif good and measured >= TRIP_LIMIT:
                alarm = "High temperature"
            if alarm:
                state = "Tripped"
                command = False
                heater = False
                reason = (f"Last good reading is {sample_age} s old."
                          if sample_age >= STALE_TIMEOUT
                          else f"Measured {measured:.1f} °C crossed {TRIP_LIMIT:.0f} °C.")
                log(second, alarm, reason + " The simulated cutoff removed heat.")

        if state == "Heating" and good and measured >= SETPOINT:
            state = "Holding"
            hold_started = second
            command = False
            heater = scenario == "heater" and stuck_seconds > 0
            log(second, "Setpoint reached", "Beginning a 12 s hold.")
            if heater:
                log(second, "Heater fault injected", "Heat output stayed on during the hold.")
        elif state == "Holding" and second - hold_started >= 12:
            state = "Cooling"
            command = False
            heater = False
            log(second, "Cooling started", "The hold finished and heat was switched off.")
        elif state == "Cooling" and good and measured <= RESET_LIMIT:
            state = "Complete"
            log(second, "Cycle complete", "The measured temperature returned to 40 °C or below.")

        safe = good and measured <= RESET_LIMIT
        samples.append(dict(second=second, state=state, value=measured, good=good,
                            age=sample_age, heater=heater, command=command, alarm=alarm, safe=safe))
        if state == "Tripped" and safe:
            log(second, "Reset temperature reached", "A fresh reading is at or below 40 °C. The alarm remains latched.")
            break
        if state == "Complete":
            break
    return {"events": events, "samples": samples}


if __name__ == "__main__":
    print(json.dumps(simulate(sys.argv[1] if len(sys.argv) > 1 else "heater"), indent=2))