Need help with timer / temperature watchdog for fridge

Hi there,

it would be great if someone could help me with a temperature alert rule for the fridge.

Basically, it should do the following:

  • IF temperature sensor detects >= 12°C THEN alert
  • repeat it until temperature goes below 11.5°C
  • but check/alert only every 20 minutes

What it does currently is that it alerts on each change :frowning: (which is a bit annoying)

var Timer   tKTemp = null       

rule "Temperaturwarnung Kuehlschrank"
    Item EG_ku_s_XiaomiTemperatursensorB_Temperature changed
    if(EG_ku_s_XiaomiTemperatursensorB_Temperature.state >= 12 | °C) {
        if(tKTemp === null)
            tKTemp = createTimer (now, [|
                    logInfo("KUEHLSCHRANK", "--> Temperaturwarnung: Kühlschrank >= 12°C / B_Temperature: "+ (EG_ku_s_XiaomiTemperatursensorB_Temperature))
                        if(VxTempFridgeAlarmnotifications.state==ON && (EG_ku_s_XiaomiTemperatursensorB_Temperature.state >= 12 | °C)) {
                            logInfo("KUEHLSCHRANK", "--> Temperaturalarm: Kühlschrank >= 12°C / B_Temperature: "+ (EG_ku_s_XiaomiTemperatursensorB_Temperature))

    } else if(EG_ku_s_XiaomiTemperatursensorB_Temperature.state < 11.5 | °C) {
            tKTemp?.cancel      //  tKTemp.cancel()
            tKTemp = null

You can use the previousState and newState implicit variables to check if the temperature is lower than it was before. Here’s a rule I use to turn my 3D printer off after the temperature has dropped below 50°C.

var newTemp = newState as Number
var previousTemp = previousState as Number

if (newTemp < previousTemp && octoPrint_Temperature_Hotend.state > 40|°C && octoPrint_Temperature_Hotend.state < 50|°C)

I also have a condition that it must be above 40°C. The reason for this is that when I turn the printer back on, the hotend will be lower than 50°C (since it’s at room temperature). So if the temperature drops at all, it’ll trigger the rule and immediately turn the printer off while I’m setting up to print.

Personally, I wouldn’t use a timer. I’d make a gatekeeper item that gets turned ON when the rule runs, with expire metadata set to 20 minutes. Then I’d have the rule check if the gatekeeper is ON before triggering a notification. But that’s just how I like doing things.

You don’t need a timer for this. Save a timestamp when you alert as the global and then test whether it’s been 20 minutes since that timestamp before sending another one.

var lastAlert = now.minusMinutes(21) // make sure the first time it breaks the threshold an alert is sent

rule "Temp alert"
    Item TempSensor changed
    // If the temp is below the threshold nothing to do
    if(TempSensor.state < 12 | °C) {

    // If we get to this point the temp is too high, send the alert if it's been long enough since the last one.
    if(lastAlert.isBefore(now.minusMinutes(20)) {
        // send the alert
        lastAlert = now

Presumably the temperature sensor is periodically reporting new temps so that will drive the repeated alerts so we don’t need a looping timer for this.

1 Like

I had no idea you could do this so easily. Thanks, Rich!


Very helpful - thanks a lot!