Executing a part of the program only once - arduino

Question

I'm designing an automatic changeover of a generator using Arduino. When the EB power is off, I need to switch on the generator starting motor for five seconds, then switch it off and then switch on the contactor C2. When the generator is ON and now if EB power comes in, I have to switch OFF the contactor C2, switch ON the generator stop motor for five seconds and then switch ON the contactor C2. My code is
int ebin = 2; // EB input
int gin = 3; // Generator input
int GonR1 = 4; // Generator ON (Relay 1) starting motor
int GoffR2 = 5; // Generator OFF (Relay 2) stopping motor
int C1 = 6; // Contactor 1
int C2 = 7; //Contactor 2
int e = 0;
int g = 0;
void setup()
{
pinMode(ebin, INPUT);
pinMode(gin, INPUT);
pinMode(GonR1, OUTPUT);
pinMode(GoffR2, OUTPUT);
pinMode(C1, OUTPUT);
pinMode(C2, OUTPUT);
}
void loop()
{
e = digitalRead(ebin);
g = digitalRead(gin);
if (e == LOW) {
digitalWrite(GoffR2, LOW);
digitalWrite(C1, LOW);
delay(4000);
digitalWrite(GonR1, HIGH);
delay(5000);
digitalWrite(GonR1, LOW);
digitalWrite(C2, HIGH);
}
else if (e == HIGH && g == LOW) {
digitalWrite(GoffR2, LOW);
digitalWrite(GonR1, LOW);
digitalWrite(C2, LOW);
digitalWrite(C1, HIGH);
}
else if (g == HIGH && e == HIGH) {
digitalWrite(GonR1, LOW);
delay(5000);
digitalWrite(C2, LOW);
digitalWrite(GoffR2, HIGH);
delay(4000);
digitalWrite(GoffR2, LOW);
digitalWrite(C1, HIGH);
}
}
When e==LOW, I want this part
digitalWrite(GoffR2, LOW);
digitalWrite(C1, LOW);
delay(4000);
digitalWrite(GonR1, HIGH);
delay(5000);
digitalWrite(GonR1, LOW);
To execute only once and I want this part
digitalWrite(C2, HIGH);
to be executed continuously until the condition fails.
But the reality is when the condition (e==LOW) is true the entire loop gets executed continuously. This will make the generator starter motor to run every 4 seconds. So I need help to solve this problem.

Answer 1

I haven't tried to understand all of your code, but this demonstrates the problem you have asked about:
You need to keep the previous state of e and if it was not LOW when the low if statement is called then you need to run the once off code:
int e = 0;
int e_previous = 1;
void setup() {
// put your setup code here, to run once:
Serial.begin(115200);
}
void loop() {
// put your main code here, to run repeatedly:
for (int i = 0; i < 10; i++) {
if (e == 0) {
if (e_previous != 0) {
Serial.println("e LOW once off");
e_previous = 0;
}
Serial.println("e LOW continual");
}
else {
Serial.println("e HIGH continual");
e_previous = 1;
}
delay(2000);
// This emulates e changing state, it isn't important to understaning the code.
if (i == 3)
e = 1;
else if (i == 6)
e = 0;
}
}
will give you:
e LOW once off
e LOW continual
e LOW continual
e LOW continual
e LOW continual
e HIGH continual
e HIGH continual
e HIGH continual
e LOW once off
e LOW continual
e LOW continual
e LOW continual
Correcting your code:
int ebin = 2; // EB input
int gin = 3; // Generator input
int GonR1 = 4; // Generator ON (Relay 1) starting motor
int GoffR2 = 5; // Generator OFF (Relay 2) stopping motor
int C1 = 6; // Contactor 1
int C2 = 7; //Contactor 2
int e = 0;
int e_previous = High; //Change the initial value to whatever makes sense
int g = 0;
void setup() {
pinMode(ebin, INPUT);
pinMode(gin, INPUT);
pinMode(GonR1, OUTPUT);
pinMode(GoffR2, OUTPUT);
pinMode(C1, OUTPUT);
pinMode(C2, OUTPUT);
}
void loop() {
e = digitalRead(ebin);
g = digitalRead(gin);
if (e == LOW)
{
if (e_previous != LOW) { //This part will be run once
digitalWrite(GoffR2, LOW);
digitalWrite(C1, LOW);
delay(4000);
digitalWrite(GonR1, HIGH);
delay(5000);
digitalWrite(GonR1, LOW);
e_previous = LOW; // This stops this inner if from being run again
}
digitalWrite(C2, HIGH);
}
else if (e == HIGH && g == LOW)
{
digitalWrite(GoffR2, LOW);
digitalWrite(GonR1, LOW);
digitalWrite(C2, LOW);
digitalWrite(C1, HIGH);
e_previous = HIGH; // Reset it
}
else if (g == HIGH && e == HIGH)
{
digitalWrite(GonR1, LOW);
delay(5000);
digitalWrite(C2, LOW);
digitalWrite(GoffR2, HIGH);
delay(4000);
digitalWrite(GoffR2, LOW);
digitalWrite(C1, HIGH);
e_previous = HIGH; // Reset it
}
else { // just in case
e_previous = HIGH; // Reset it
}
}