If with a time delay

Setup, Configuration and Use Beginners
1

I have a string, and when that string get an update to the value “A” - then I would like a rule that checks if the stings get an update to value “B” - If the string does not get an update to the value “B” within 40 seconds then I would like to execute: sendCommand(Relay_Switch, “OFF”).

The problem is that I have no idea how to write such a script, can any one help me?

2

Break the job down.

Fire a rule from string update.
Check to see if value is “A”, if so start (or restart) a timer.
Else
Check to see if value is “B”, if so is the timer running, if so do the task.

You’ll need to set up a global variable to hold the timer so that it is visible to different runs of the same rule.

The timer doesn’t need to do anything, except null itself on completion.

3 
var Timer timer = null

rule "timmer string"
when
    Item timmerstring changed to "A"
then
    if (timer === null) {
        timer = createTimer(now.plusSeconds(40), [ |
            if (timerstring.state.toString != "B") {
                Relay_Switch.sendCommand(OFF)
                timer = null
            }
        ] )
    }
end
4 
var Timer timer = null                                               // define a timer

rule "timmer string"
when
    Item timmerstring changed                                        // Item changed
then
    if (timmerstring.state.toString == "A" && timer === null)        // String = "A"? Timer not started?
        timer = createTimer(now.plusSeconds(40), [ |                 // Create the timer
            Relay_Switch.sendCommand(OFF)                            // switch off and
            timer = null                                             // reinitialize timer
        ] )
    else if (timmerstring.state.toString == "B" && timer !== null) { // String is "B" and timer started
        timer.cancel                                                 //  stop timer and
        timer = null                                                 // reinitialize timer
    }
end

Timer has to be cancelled, because the string can change more than once in 40 seconds!