Help, I want to turn relay constantly on until a difference is detected, but triggered only one instead

Question

Help, I want to use arduino to control relay for electricity, i get data from a sensor and when a value is detected it should be constantly on until another detection triggered again, i can get the program to work but triggered only once instead when it should be constantly turned on, here'e my code:

int Pinout = 13;

void setup() {
    Serial.begin(9600);
    pinMode(Pinout, OUTPUT);
}

void loop() {
    int val = analogRead(A0);
    if (val <= 500) {
        digitalWrite(Pinout, LOW);
    }
    else {
        digitalWrite(Pinout, HIGH);
    }
}

the relay i am using is a chinese relay module with 3 pin and VCC and GND connected to external power supply, and INput pin to 13 digital pin Arduino and the relay is which i believed is Active LOW, and for analog read i am using moisture sensor

Answer 1

As far as I can see, the relay will stay on when val is less or equal than 500, and stay off when val is higher than 500.

However, there might be a problem when val keeps fastly moving around 500; it will switch on and off quite fast.

To prevent this, you should make two 'triggers', e.g. turn it on when the value <= 480, and turn it off when the value >= 520. When it is in between 480 and 520 it will not change. This will cause less fast changes of the relay. Of course if the initial value is already between 480 and 520 you have to make a choice yourself.