Arduino - multiple LEDs with different delays

Question

Hi all

I'm trying to write code to get 3 LEDs flashing independently, each with a different ON and OFF period.

For example:

LED1: ON for 25 ms, OFF for 500 ms

LED2: ON for 50 ms, OFF for 800 ms

LED3: ON fo 100 ms, OFF for 300 ms

So far I have set up the hardware: 3 LEDs on digital pins 6, 7 and 8 using my Arduino UNO board and a breadboard.

Code-wise I understand that I can't use the "delay" function because it causes the whole system to delay i.e. causes 'blocking'. At the moment I'm using the millis() function. My problem is that at the moment my code causes LED1 to turn ON for 25 ms and off for 25 ms, LED2 turns ON for 50 ms and off for 50 ms etc. So I need to somehow alter the OFF period independently.

In summary: I need a new approach or an alteration to my code to be able to independently change the ON and OFF periods for each of my LEDs independently.

Here is my code so far:

[code]

// Which pins are connected to which LED

const byte LED1 = 6;

const byte LED2 = 7;

const byte LED3 = 8;

// Assigning delays.

const unsigned long LED1_interval = 25;

const unsigned long LED2_interval = 50;

const unsigned long LED3_interval = 100;

// Declaring the variables holding the timer values for each LED.

unsigned long LED1_timer;

unsigned long LED2_timer;

unsigned long LED3_timer;

// Setting 3 digital pins as output pins and resetting timer

void setup ()

{

pinMode (LED1, OUTPUT);

pinMode (LED2, OUTPUT);

pinMode (LED3, OUTPUT);

LED1_timer = millis ();

LED2_timer = millis ();

LED3_timer = millis ();

} // end of setup

//LED1 loop that turns it ON if it is OFF and vice versa

void toggle_LED1 ()

{

if (digitalRead (LED1) == LOW)

digitalWrite (LED1, HIGH);

else

digitalWrite (LED1, LOW);

// remember when we toggled it

LED1_timer = millis ();

} // end of toggleLED_1

//LED2 loop

void toggle_LED2 ()

{

if (digitalRead (LED2) == LOW)

digitalWrite (LED2, HIGH);

else

digitalWrite (LED2, LOW);

// remember when we toggled it

LED2_timer = millis ();

} // end of toggle_LED2

//LED 3 loop

void toggle_LED3 ()

{

if (digitalRead (LED3) == LOW)

digitalWrite (LED3, HIGH);

else

digitalWrite (LED3, LOW);

// remember when we toggled it

LED3_timer = millis ();

} // end of toggle_LED3

void loop ()

{

// Handling the blink of LED1.

if ( (millis () - LED1_timer) >= LED1_interval)

toggle_LED1 ();

// Handling the blink of LED2.

if ( (millis () - LED2_timer) >= LED2_interval)

toggle_LED2 ();

// Handling the blink of LED3.

if ( (millis () - LED3_timer) >= LED3_interval)

toggle_LED3 ();

/* Other code that needs to execute goes here.

It will be called many thousand times per second because the above code

does not wait for the LED blink interval to finish. */

} // end of loop

[/code]

Any help would be greatly appreciated because I'm [b]very[/b] new to this!

Thanks!

billabott · Answer

Most Arduino boards have two external interrupts: numbers 0 (on digital pin 2) and 1 (on digital pin 3). Official Arduino.cc Example int pin = 13 ; volatile int state = LOW ; void setup ( ) { pinMode ( pin , OUTPUT ) ; attachInterrupt ( 0 , blink , CHANGE ) ; //0 is digtal pin 2 } void loop ( ) { digitalWrite ( pin , state ) ; } void blink ( ) { state = ! state ; } Observing that all your time factors are multiples of 25 ms, I would suggest that you use a digital pin on your UNO to initiate a self generated external interrupt. Adding code: const byte iSignal =9; Adding physical wire/resister+LED/cap. between pins 9 and 2. Here is the guts of it: pin 9 is pulsed every 25 ms by your loop(), the iHandler() bumps a counter, the main loop() has a case statement that allows the required LED transistion actions to take place depending on the counter value only when old_counter is not equal to counter. 0 <= counter <= 32 (because 800/25=32), reset counter to 0 after 32 interrupts have occurred. (I am not sure if you want to count to 32 or 31.) To make the implementation easier(reliable) change LED1: ON for 25 ms, OFF for 500 ms LED2: ON for 50 ms, OFF for 800 ms to LED1: ON for 25 ms, OFF for 450 ms LED2: ON for 50 ms, OFF for 750 ms FYI: http://arduino.cc/en/Reference/AttachInterrupt Then again, you could just call the iHandler directly without the external interrupt - but what fun would that be?

Former Member · Answer

Hi muteprint, I looked a little closer at your code, and see a few problems: In toggle_LED1ii () you have: LED1_statechange_Timei = millis (); // Remember when LED1's state was changed from OFF to ON but that should be Timeii (two i's). Similarly, in toggle_LED2i () you have: LED2_statechange_Timeii = millis (); // Remember when LED2's state was changed from ON to OFF but that should be Timei (one i). Also, in setup(), I think you need to initialize the Timeii statechange variables, in order to prevent referring to random values in the loops. Billabott is probably right that by using pointers you can condense the code, but I haven't looked at that closely, and I think you probably want to get it working first, and then improve it later.

mixx · Answer

Wait a second... Nobody realized that you're trying to read an output? I'm almost 100% sure that's a no-no. You have to store the state in another variable. I'd suggest using arrays and just making it into one function. You can make a boolean array to store the states more easily, and advance the index using an increment in the loop. Either way, just store the state in a variable. I also just noticed the OP is from 2013, but I feel other people might check this forum for solutions so, here. This should work, I tested it on my uno. I also worked on a variation of this myself and i'll post it after I give it to my professor so it doesn't show up in an originality report haha. Here: // Which pins are connected to which LED const byte LED1 = 6; const byte LED2 = 7; const byte LED3 = 8; // Assigning delays. const unsigned long LED1_interval = 25; const unsigned long LED2_interval = 50; const unsigned long LED3_interval = 100; // Declaring the variables holding the timer values for each LED. unsigned long LED1_timer; unsigned long LED2_timer; unsigned long LED3_timer; //Saving states of led's in an array + index bool states[4] = {0, 0, 0, 0}; int index = 0; // Setting 3 digital pins as output pins and resetting timer void setup () { pinMode (LED1, OUTPUT); pinMode (LED2, OUTPUT); pinMode (LED3, OUTPUT); LED1_timer = millis (); LED2_timer = millis (); LED3_timer = millis (); } // end of setup //LED1 loop that turns it ON if it is OFF and vice versa void toggle_LED1 () { if (states[index] == LOW){ digitalWrite (LED1, HIGH); states[index] = HIGH; } else{ digitalWrite (LED1, LOW); states[index] = LOW; } // remember when we toggled it LED1_timer = millis (); } // end of toggleLED_1 //LED2 loop void toggle_LED2 () { if (states[index] == LOW){ digitalWrite (LED2, HIGH); states[index] = HIGH; } else{ digitalWrite (LED2, LOW); states[index] = LOW; } // remember when we toggled it LED2_timer = millis (); } // end of toggle_LED2 //LED 3 loop void toggle_LED3 () { if (states[index] == LOW){ digitalWrite (LED3, HIGH); states[index] = HIGH; } else{ digitalWrite (LED3, LOW); states[index] = LOW; } // remember when we toggled it LED3_timer = millis (); } // end of toggle_LED3 void loop () { // Handling the blink of LED1. if ( (millis () - LED1_timer) >= LED1_interval) toggle_LED1 (); index++; // Increment Index // Handling the blink of LED2. if ( (millis () - LED2_timer) >= LED2_interval) toggle_LED2 (); index++; // Increment Index // Handling the blink of LED3. if ( (millis () - LED3_timer) >= LED3_interval) toggle_LED3 (); index = 0; // Reset index to 0 for next run /* Other code that needs to execute goes here. It will be called many thousand times per second because the above code does not wait for the LED blink interval to finish. */ } // end of loop Edit: Ahh yes, forgot I said I'd post my own code that tackles this problem. Here it is, I seem to have some weird issues when initializing the states at low, and I also seemed to have another weird issue when running this that required adding a delay to setup. This solves it for some reason. I haven't looked into it all that much. If anyone knows what might be causing these issues please message me/reply to my post. // Variable Inits int led[4] = {4, 5, 6, 7}, count = 0, cot = 0; // Create array with led pins and int 'count' bool states[4] = {1, 1, 1, 1); // Create a boolean array to store led states unsigned long prevTime[5], currTime; // Create an array to store the previous time an led is checked, and // a variable to store the current time when checked for each loop long off[4] = {100, 600, 2100, 3600}; // Create an array to store how long led's should be off long on[4] = {400, 400, 400, 400}; // Create an array to store how long led's should be on #define ledcount (sizeof(led)/sizeof(led[0])) // Use define to return the size of the array of led pins when calling 'ledcount' // 'sizeof()' returns the size in bytes of a variable. For an array, // you can take the total size of the array, and divide by the size // of a single element to get the amount of values in the array void setup() { delay(1); for(int i = 0; i <= ledcount; i++){ // Initialize led pins as outputs pinMode(led[i], OUTPUT); } //Serial.begin(115200); } void loop() { currTime = millis(); // Save the current time in milliseconds since the program started running for(int i = 0; i <= ledcount; i++){ // Loop through each led and turn it on, off, or leave it alone changeLED(i, currTime); } } void changeLED(int place, unsigned long Time){ if((states[place] == 1) && ((Time - prevTime[place]) >= on[place])){ // If the led has been on for the desired // amount of time, turn it off //Serial.println("Buoy " + String(place+1) + ": Off, Time Since last check: " + String(Time - prevTime[place])); prevTime[place] = Time; // Save time that led was changed states[place] = 0; // Save state of led } else if((states[place] == 0) && ((Time - prevTime[place]) >= off[place])){ // If the led has been off for the // desired amount of time, turn it on if(place != 0){ // If we're not changing the first led, just turn it on and save the time/state //Serial.println("Buoy " + String(place+1) + ": On, Time Since last check: " + String(Time - prevTime[place])); prevTime[place] = Time; states[place] = 1; } else{ // Since the first led has an extra delayed blink, it gets special treatment if((count == 1) || (count == 6) || count == 18){ // If count is 1, 4, or 18 turn on the led. multiply count by 100 // and you'll get the time in milliseconds. count increments every states[place] = 1; // 100 milliseconds when the LED hasn't been turned off. //Serial.println("Buoy " + String(place+1) + ": On, Time Since last check: " + String(Time - prevTime[place])); } if(count == 48){ // if 6 seconds have passed since pattern started, reset the count for next sequence count = 0; } count++; // Increment count and save time prevTime[place] = Time; } } digitalWrite(led[place], states[place]); }

billabott · Answer

Sorry, no, I am out of ideas . I will, however, share with you that there are other uC that have multiple timers on board that can be configured to generate interrupts at any predetermined interval. Q: Just out of curiosity, what exactly controls the periodicity of your LEDs? Or in other words; "What is your application, eh?" You might simplify your program by adopting a more conventional approach by using boolean LED1_state = false; // place these very near the top of script so their scopes are GLOBAL boolean LED2_state = false; boolean LED3_state = false; If time to turn off LED1 Set LED1_on_timer to milles() +800; // turning off; so it is known when to turn it on again. toggle_LED(&LED1, &LED1_state); // call function to toggle LED between 1 and 0 Set LED1_off_timer to milles() +2048; // presumeably will be reset to a correct value // after turning LED1 on prior to the expiration of this value else if time to turn on LED1 Set LED1_off_timer to milles() +50; // turning on; so it is known when to turn it off again. toggle_LED(&LED1, &LED1_state);; // call function to toggle LED between 0 and 1 Set LED1_on_timer to milles() +2048; // presumeably will be reset to a correct value // after turning LED1 off prior to the expiration of this value void toggle_LED(int *LEDxP, boolean *LEDxP_state) // will need ONLY this one function to toggle ANY LED since pointers are used { digitalWrite (*LEDxP, (* LEDxP_state = !(* LEDxP_state) )); // see note below } // End of toggle_LED note : According to http://arduino.cc/en/Reference/BooleanVariables digitalWrite does accept boolean arg of true/false in lieu of HIGH/LOW arg. Message was edited by: William Bottger

Former Member · Answer

Even with using only one timer, you may be able to do something like this: You have 6 events to schedule (turning each of 3 LED's On and Off). For each event, you need to store 4 fields: which LED, On vs. Off, the time-of-day the event should be taken next, and the amount of time between events. For LED1, the time between events would be 525 ms. You can store these 6 events in an array. (They don't have to be sorted in any particular order.) It may help to think of this array as the "delay-queue" of a task scheduler. Then you can write a function that will scan this array and find the event with the soonest next time-of-day. Set an interrupt timer for that time-of-day. While waiting for the timer, any work can be going on. When the timer goes off, turn the specified LED On or Off, and update the next time-of-day field by adding the specified time between events for that LED. Loop back and scan the array again to find the next soonest event.

Arduino - multiple LEDs with different delays

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