Phone alert when your mains voltage goes too high or too low

1// Mains voltage alert: tells your phone through ntfy when the supply voltage stays2// outside the Australian range, and again when it's back. Needs a Shelly energy meter.3 4let CONFIG = {5  highVolts: 253,6  lowVolts: 216,7  holdSec: 60,8  ntfyTopic: "",9  meterId: 0,10};11 12// Read the meter every 5 seconds, so a short spike is seen without filling the log.13let READ_EVERY_SEC = 5;14// The voltage has to come this far back inside the range before the all-clear,15// so a reading that sits right on the limit can't send alert after alert.16let RECOVER_VOLTS = 2;17// Unsent messages are kept and retried after each reading, up to this many.18let MAX_QUEUED = 10;19 20let outSince = 0;21let alerted = false;22let worst = 0;23let queue = [];24let sending = false;25let warnedNoMeter = false;26 27function readVolts() {28  let s = Shelly.getComponentStatus("em1", CONFIG.meterId);29  if (s === null || typeof s.voltage !== "number") return null;30  return s.voltage;31}32 33function onSent(res, err) {34  sending = false;35  if (err === 0 && res.code === 200) {36    queue.splice(0, 1);37    sendNext();38  } else {39    print("Couldn't reach ntfy. Will try again shortly.");40  }41}42 43function sendNext() {44  if (sending || queue.length === 0 || CONFIG.ntfyTopic === "") return;45  sending = true;46  Shelly.call("HTTP.Request", {47    method: "POST",48    url: "https://ntfy.sh/" + CONFIG.ntfyTopic,49    body: queue[0],50    headers: { "Content-Type": "text/plain" },51    timeout: 15,52  }, onSent);53}54 55function alert(msg) {56  print(msg);57  if (queue.length >= MAX_QUEUED) queue.splice(0, 1);58  queue.push(msg);59}60 61function isWorse(v) {62  if (worst === 0) return true;63  if (v > CONFIG.highVolts) return v > worst;64  return v < worst;65}66 67function check() {68  let v = readVolts();69  if (v === null) {70    if (!warnedNoMeter) print("No voltage reading. Check meterId.");71    warnedNoMeter = true;72    return;73  }74  warnedNoMeter = false;75  let now = Shelly.getComponentStatus("sys").uptime;76  let out = v > CONFIG.highVolts || v < CONFIG.lowVolts;77  let recovered = v <= CONFIG.highVolts - RECOVER_VOLTS && v >= CONFIG.lowVolts + RECOVER_VOLTS;78 79  if (out) {80    if (outSince === 0) {81      outSince = now;82      worst = 0;83      print("Voltage " + v.toFixed(1) + " V is outside " + CONFIG.lowVolts + "-" +84        CONFIG.highVolts + " V. Watching.");85    }86    if (isWorse(v)) worst = v;87    if (!alerted && now - outSince >= CONFIG.holdSec) {88      alerted = true;89      alert("Mains voltage is " + (v > CONFIG.highVolts ? "high" : "low") + ": " +90        v.toFixed(1) + " V for over " + CONFIG.holdSec + " s (range " +91        CONFIG.lowVolts + "-" + CONFIG.highVolts + " V).");92    }93  } else if (outSince !== 0 && (recovered || !alerted)) {94    if (alerted) {95      let secs = now - outSince;96      let took = secs < 60 ? "under a minute" : "about " + Math.round(secs / 60) + " min";97      alert("Mains voltage is back to " + v.toFixed(1) + " V after " + took +98        ". It reached " + worst.toFixed(1) + " V.");99    } else {100      print("Voltage back to " + v.toFixed(1) + " V before the hold time. No alert.");101    }102    outSince = 0;103    alerted = false;104  }105  sendNext();106}107 108Timer.set(READ_EVERY_SEC * 1000, true, check);109print("Voltage alert started. Range " + CONFIG.lowVolts + "-" + CONFIG.highVolts +110  " V, alert after " + CONFIG.holdSec + " s outside it.");111check();