I found a solution and I would like to show it !
[{"id":"3a3cc25a.14183e","type":"tab","label":"Flow 1","disabled":false,"info":""},{"id":"74fd26b6.b14468","type":"function","z":"3a3cc25a.14183e","name":"Data Generation","func":"flow.set(\"counter\", 20);\nreturn msg;","outputs":1,"noerr":0,"initialize":"","finalize":"","x":340,"y":100,"wires":[["c3041f59.7568b"]],"info":"Ορίζεται μία μεταβλητή counter η οποία έχει αριθμητική ακέραια τυχαία τιμή από 20 έως 60 και προσομειώνει την τιμή της θερμοκρασίας. Είναι flow διότι χρειάζεται να υπάρχει πρόσβαση σε αυτή και από άλλους κόμβους και στο τέλος επιστρέφεται ως msg. "},{"id":"2cc5af72.77e9d","type":"inject","z":"3a3cc25a.14183e","name":"Temperature Sensor","props":[],"repeat":"","crontab":"","once":false,"onceDelay":0.1,"topic":"","payloadType":"str","x":130,"y":100,"wires":[["74fd26b6.b14468"]],"info":"Μόλις ο κόμβος \"Inject\" ενεργοποιηθεί, λαμβάνεται μία μέτρηση κάθε ένα λεπτό."},{"id":"4ffcbf9e.49c86","type":"ui_gauge","z":"3a3cc25a.14183e","name":"Temperature Adjustment","group":"2d70c600.e2d54a","order":6,"width":0,"height":0,"gtype":"gage","title":"Temperature","label":"Celsius","format":"{{value}}","min":"0","max":"20","colors":["#00b500","#e6e600","#ca3838"],"seg1":"","seg2":"","x":1010,"y":160,"wires":[]},{"id":"3521b71d.5019e8","type":"function","z":"3a3cc25a.14183e","name":"Fire ","func":"//Στις παρακάτω εντολές γίνεται μία προσομοίωση εξασθένησης της \n//πυρκαγιάς που είναι ενεργή στο χώρο του θεάτρου. Η τιμή της \n//μεταβλητής counter υποδηλώνει τη θερμοκρασία και αν αυτή είναι \n//μικρότερη του 20 αυτό σημαίνει ότι το σύστημα ψεκασμού είχε ήδη\n//ενεργοποιηθεί και έχει σβήσει. Αν όχι, τότε μειώνεται κάθε φορά \n//ενδεικτικά κατά 1, εφόσον ταυτόχρονα λειτουργεί και το σύστημα \n//ψεκασμού που είναι ένας κόμβος switch. Με τη μείωση της \n//υποδηλώνεται ότι η πυρκαγιά εξασθενεί.\nvar counter = flow.get('counter')\nmsg.payload = counter; \nif(counter<0)\n{\n return 0;\n}\nelse\n{\ncounter=counter-1;\n}\nflow.set(\"counter\",counter);\nreturn msg; ","outputs":1,"noerr":0,"initialize":"","finalize":"","x":770,"y":120,"wires":[["4ffcbf9e.49c86","21ea5e6e.5a46f2","f49fc8f7.dd15a8"]]},{"id":"21ea5e6e.5a46f2","type":"switch","z":"3a3cc25a.14183e","name":"Reset Switch","property":"payload","propertyType":"msg","rules":[{"t":"eq","v":"0","vt":"num"}],"checkall":"true","repair":false,"outputs":1,"x":570,"y":220,"wires":[["4e724087.6c654"]]},{"id":"4e724087.6c654","type":"function","z":"3a3cc25a.14183e","name":"Reset Function","func":"msg.payload=0;\nreturn msg;","outputs":1,"noerr":0,"initialize":"","finalize":"","x":580,"y":160,"wires":[["c3041f59.7568b"]]},{"id":"c3041f59.7568b","type":"trigger","z":"3a3cc25a.14183e","name":"Trigger","op1":"counter","op2":"counter-1","op1type":"flow","op2type":"flow","duration":"-1","extend":false,"overrideDelay":false,"units":"s","reset":"0","bytopic":"all","topic":"topic","outputs":1,"x":560,"y":100,"wires":[["3521b71d.5019e8"]],"info":"Με τον κόμβο trigger γίνεται η υπόθεση ότι κάθε 1 δευτερόλεπτο μειώνεται η υψηλή θερμοκρασία που είναι αποτέλεσμα της πυρκαγιάς, κατά 1 βαθμό κελσίου."},{"id":"f49fc8f7.dd15a8","type":"debug","z":"3a3cc25a.14183e","name":"","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"payload","targetType":"msg","statusVal":"","statusType":"auto","x":950,"y":100,"wires":[]},{"id":"2d70c600.e2d54a","type":"ui_group","name":"Monitoring","tab":"c0a2130d.da022","order":1,"disp":true,"width":"6","collapse":false},{"id":"c0a2130d.da022","type":"ui_tab","name":"Alarm","icon":"dashboard","disabled":false,"hidden":false}]
