Blinking LED - how to implement it correctly?

[Michal_Szymanski]

In my installation when I receive signal from flood sensor I will activate blinging led.
Because I have many sensors I have several similar sections:

rule "FloodAlarm_BathroomLower_Activated"
    when
    	Item FloodSensorLazienkaDolna changed from OFF to ON or
        Item FloodSensorLazienkaDolna changed from NULL to ON
	then
		<activate blinking led>
		floodAlarmIsActivated = true 	 
		...
end


// FloodAlarm activation BathroomUpper (edge activated)
rule "FloodAlarm_BathroomUpper_Activated"
    when
    	Item FloodSensorLazienkaGorna changed from OFF to ON or
        Item FloodSensorLazienkaGorna changed from NULL to ON
	then
		<activate blinking led>
		floodAlarmIsActivated = true 	 
		...
end

…

I’ve found script that implement blinking behaviour

Alarmclock whit blinking Light

This isn’t quite so straight forward as you might think. If your light is an Item called “Light” and your switch is an Item called “AlarmSwitch”: NOTE: I just typed this in, there may be errors, I’m missing the imports var Timer lightsBlinkingTimer = null rule "Alam Lights" when Item Alarm_MasterEvent received command ON then if(lightsBlinkingTimer != null) { lightsBlinkingTimer.cancel lightsBlinkingTimer = null } lightsBlinkingTimer = createTimer(now.plusSec…

but I do not add the same code for each sensor - I would have one place where I put ‘blinking logic’ script, I do not want to put such part in each rule:

if(lightsBlinkingTimer != null) {
        lightsBlinkingTimer.cancel
        lightsBlinkingTimer = null
    }

    lightsBlinkingTimer = createTimer(now.plusSeconds(1), [|
        Light.sendCommand(if(Light.state == ON) OFF else ON)
        lightBlinkingTimer.resechedule(now.plusSeconds(1))
    ])

I wanted to make to rule on changes floodAlarmIsActivated variable but such rule cannot be accepted.
What is best way to do it?

[rlkoshak (Rich Koshak)]

Design Pattern: Separation of Behaviors

Edit: Updated for OH 4. Please Design Pattern: What is a Design Pattern and How Do I Use Them for more information on what a DP is and how to use them. Problem Statement Often one will have certain cross cutting code that is used across a many diverse and varied collection of Rules. Such code can include things like calculating time of day to control the behavior of a rule, sending alerts, calculating state to drive a state machine, etc. For example, Lighting, blind/rollershutter controls and …

Or

Reusable Functions: A simple lambda example with copious notes

Major Edit: Rewrote with the cleaner OH 2.3 syntax. The example lambda on the OH 1 wiki is overly complex and as written will not work in OH 2. This quick example will show a super simple lambda example with copious notes. Here is the code without comments. It takes in an Item, logs it’s state and returns a slightly modified version of the String logged. val log= [ GenericItem s | logInfo("lambda", s.state.toString) s.state.toString + " logged" ] rule "Call Lambda" when // some t…

[Michal_Szymanski]

Thank you.
I also found out that I can use time based trigger that start every second and inside that triger check if variable floodAlarmIsActivated is set to true and then on or off LED. I know that cron is limited to second but in this example it is not a problem. I think it should work.

[JAVI (JAVIER NOTO)]

this code works well for me

var Timer TimerH = null

rule "Alarma automática"
when
Item Detector_Gas changed to ON
then
if(TimerH != null) {
TimerH.cancel
TimerH = null
}

TimerH = createTimer(now.plusSeconds(1)) [|
    if(Alarma.state==ON){
            Alarma.sendCommand(OFF)
    }
    else{
            Alarma.sendCommand(ON)
    }
    TimerH.reschedule(now.plusSeconds(1))
]

end

rule "Apagado de alarma automática"
when
Item Detector_Gas changed to OFF
then
Alarma.sendCommand(OFF)
if(TimerH != null) {
TimerH.cancel
TimerH = null
}
end

[stefan.hoehn (Stefan Höhn)]

I know this is an old thread but rather than opening up a new one…I think my question does relate to that topic.

I just created a rule that toggles a virtual item every other second, so I can use it as a blinker wherever I want

triggers:
  - id: "1"
    configuration:
      cronExpression: "* * * * * ? *"
    type: timer.GenericCronTrigger
conditions: []
actions:
  - inputs: {}
    id: "2"
    configuration:
      type: application/javascript
      script: |
        if (itemRegistry.getItem('Blinker').getState() == 'ON') {
          events.sendCommand('Blinker', 'OFF');
        } else {
          events.sendCommand('Blinker', 'ON');
        }
    type: script.ScriptAction

which brings me to my questions:

• is it really a “good” idea to run a rule every other second?
• By toggling this virtual item it basically spams my logs which also doesn’t really look healthy

2021-01-22 18:26:18.989 [INFO ] [openhab.event.ItemStateChangedEvent ] - Item 'Blinker' changed from ON to OFF
2021-01-22 18:26:19.001 [INFO ] [openhab.event.ItemCommandEvent      ] - Item 'Blinker' received command ON
2021-01-22 18:26:19.006 [INFO ] [openhab.event.ItemStateChangedEvent ] - Item 'Blinker' changed from OFF to ON
2021-01-22 18:26:19.500 [INFO ] [openhab.event.ItemCommandEvent      ] - Item 'Blinker' received command OFF
2021-01-22 18:26:19.505 [INFO ] [openhab.event.ItemStateChangedEvent ] - Item 'Blinker' changed from ON to OFF#
````

Any ideas?

[rlkoshak (Rich Koshak)]

@stefan.hoehn

is it really a “good” idea to run a rule every other second?

Well, in general it’s not really “bad”. But it’s not great. We should endeavor to avoid writing rules that do nothing most of the time. This is also sometimes called polling. It’s much better to instead react to events and only do work when necessary instead of always doing something even when you don’t need to. The code tends to be simpler to understand and maintain and you avoid being wasteful with resources.

However, is it really bad to do this? No, not really. You’ll be spamming the logs, sure and that can add up to wearing out an SD card a little faster. And you’ll be using probably a barely measurable more amount of energy per day. But those are not really that bad of a problem.

So what is someone to do? You have a number of options actually. A couple are:

• Create another Switch Item to enable the Blinker. Add a Condition to the rule so it only runs when that Switch is ON.

• Implement the Blinker as a Design Pattern: Looping Timers. Trigger a rule only when something should start blinking and then create a looping timer to blink it until it’s told to stop. There is an OH 3 compatible implementation of looping timer as a library at https://github.com/rkoshak/openhab-rules-tools/tree/main/looping_timer.

[stefan.hoehn (Stefan Höhn)]

Thanks Rich,

the intent was to have a blinker item that I can use with a logic and to make icons blink on the UI (for example an alarm) without using much logic - instead I would have just used a logical and with the blink to let my icon toggle visibility.

but yes I could somehow write a rule that makes sure the “blinker” will only start when any alarm item goes on and then using the approach you have provided.

Thanks for sharing your thoughts - always appreciated!