0

I have a very basic programming knowledge, but the thing I want to achieve is to alternate between switching 2 relays with a button or a RPi input pulse.

So something like this:

  1. Press the button
  2. Switch relay 1 on and off (1 second delay)
  3. Press the button
  4. Switch relay 2 on and off
  5. Press the button
  6. Switch relay 1 on and off (1 second delay)
  7. Press the button
  8. Switch relay 2 on and off
  9. Press the button
  10. Switch relay 1 on and off (1 second delay)
  11. Press the button
  12. Switch relay 2 on and off
  13. etc.

Here's my code, I thought if I'd just put the second relay after the first else everything would work. But I'm missing some basic knowledge to figure this out.

const int ledPin = 2;
const int ledPinA = 3;

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

void loop() {
  int sensorValue = analogRead(A0);
  Serial.println(sensorValue);
  delay(1);
  if (sensorValue > 500) {
    digitalWrite(ledPin, HIGH);
  } else {
    digitalWrite(ledPin, LOW);
  }
  if (sensorValue > 500) {
    digitalWrite(ledPinA, HIGH);
  } else {
    digitalWrite(ledPinA, LOW);
  }
}

I'm thinking I should use while.

  • Do you want it to swtch the relay on ONCE or repeatedly (so make them blink)? – frarugi87 Sep 14 '17 at 15:11
0

So something like this:

easy:

  1. increment a counter based on button presses;

  2. run a state machine on that counter to decide on relay actions.

the state machine can be a simple switch / case statement.

  • Thank you dannyf. It was simple indeed. Made a counter, ==1 switches relay 1 and ==2 switches the other and resets the counter. – user31208 Sep 15 '17 at 18:42
1

The way you have it, both if blocks will be evaluated each time you call to loop(). Instead, you need to create a variable that remains "alive" in between each call to loop() to keep track of which relay you want to activate:

const int ledPin = 2;
const int ledPinA = 3;
int active_relay = 2;   // State variable for current relay pin

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

void loop() {
      int sensorValue = analogRead(A0);

      Serial.println(sensorValue);

      delay(1);    // This delays for 1ms, not 1s ??

      if (sensorValue > 500) {   // Pulse received
          digitalWrite(active_relay, HIGH);  // Relay on
          delay(1000);                       // Wait 1 second
          digitalWrite(active_relay, LOW);   // Relay off

          // Update variable for next call to loop
          if (active_relay == ledPin) {
              active_relay = ledPinA;      // Swap
          }
          else {
              active_relay = ledPin;       // Swap
          }
      }
      // Remove 2nd if block
}
  • I'd use the digital reading of the pin with some debounce; if the read value must be analog (but only the OP knows this) maybe a bit of filtering is needed – frarugi87 Sep 14 '17 at 15:12

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.