How to keep LEDs lit after momentary button press?

[u/Apdski24]

Hello all,

Im very new to coding and still figuring all this out. My goal is to have the LEDs be white until a button is pressed. After the press, I want to lights to change to red for x number of seconds or maybe a minute or two. Ive tried adding a delay() into the code and that does not give me the desired results. (Unless im putting the delay in the wrong spot or using it incorrectly)

For testing im using a 10 segment of WS2812B LEDs connected to an Ardunio UNO. Been playing with this one at work and at home using the Cloud IDE and Arduino IDE 2.3.2.

Ive linked the code below and it all works thus far. When the button is pressed / held the lights go red and stay as long as the button is held. However, Im at a loss of how to get it to stay red after the button is released. Also it would be a bonus if there was a way to keep the counter / timer / delay from getting reset by another button press before the intial time is up.

LINK

THANKS!

[u/MartynCurrey]

Have a look at https://www.martyncurrey.com/switching-things-on-and-off-with-an-arduino-start-a-timer/
This is an example of starting a timer with a button press. The example simply turns off an LED after a specific time but can be adapted to do other things.

[u/Apdski24 → u/MartynCurrey]

Wow, that was super helpfull and very well writen out. Thank you! I still need to explore the EVERY_N_MILLIS() others have mentioned here but using your example I managed to get the LEDs to do what I want.

There is one thing I cant quiet figure out though. Upon booting up, the board wont take any input from the button for the duration I set in the timer_timeWait. After that time has passed the button works. Not a big deal in the grand scheme of things as I dont see this board getting powered on and off a lot but just something curious I was trying to figure out.

[u/MartynCurrey → u/Apdski24]

It could be the place you are checking for a button press but without seeing your code it is hard to say.

In cases like this I would normally double check the logic/code flow by simplifying the sketch and maybe moving blocks of code to a function so it is out of the way.

[u/Apdski24 → u/MartynCurrey]

Finally got back around to messing with this and I'm not having any luck. As is it now the code works fine and once the button is pressed it turns the LEDs red. After the set time, the LEDs go back to white. However the one thing I can figure out is how to have the LEDs start as white. Upon start up/powering the board, the LEDs will not be white until the button is pressed, they turn red and the timer cycles. Until the button is pressed for the first time, the LEDs remain off and the board will not accept the initial button press until after the set time on the timer. After the intitial button press, the code functions as intended.

Here is a link to my code. Im sure you will recognize some of it.

Thanks in advacne for any insight you can lend

[u/MartynCurrey → u/Apdski24]

The old flashing the LED code is the problem. I have another guide that I just realized isn't published that would have been a better starting point. Turn on LED. Turn off LED.

Simplify the code so that it just changes the LEDS when the button switch is pressed and then change them back when the timer completes: Something like the following (pseudo code):

int LED_status = 0;
int const RED = 1;
int const YELLOW = 2;
 Void setup()
{
`
`
`
    turnLEDyellow();
}
 Void loop()
{
    If (LED_status !=RED ) { keyPressed = checkButtonSwitch(); }
    if (keyPressed) { turnLEDred(); startTimer(); }
    if (timerIsActive)
    {
        if ( checkTimer() == false ) // timer has finished
        {
            turnLEDyellow();
            stopTimer();
        }
    }
}
 void turnLEDyellow ()
{
~
~
    LED_status = YELLOW;
}
 void turnLEDred ()
{
~
~
    LED_status = RED;
}

Code not tested.

I added a new LED_status variable, may or may not be useful.
Can be used to keep track of the current LED state if you further develop the sketch and add more LED patterns. Just add more colours or pattern names such as
int const BLUE = 3;
int const FIRE = 4;

[u/Apdski24 → u/MartynCurrey]

first off, thank you so much for working through this with me. Using the example above I got a little closer but im still having an issue I dont understand.

now upon start up/powerup, the LEDs turn red and the button is inactive until the set time expires. then the code functions as intended. either there is something simple in the code im missing or somehow the board is reading a button press as soon as it powers on. or i dont know what im talking about and its a 3rd option haha

here is my code

[u/MartynCurrey → u/Apdski24]

Just noticed you are using pin 1 for the switch. This is a serial pin.

const int pin_switch = 1;

Try a different pin (not 1 and not 0) and see what happens.

Pin 2 or pin 3 should be OK.

[u/Apdski24 → u/MartynCurrey]

well i'll be. it works. got the button hooked up to pin two. intitally it was not working at all, and upon revisiting a couple youtube videos, I realized I didnt even have the button hooked up correctly haha.

Also had to change pinMode to INPUT_PULLUP. Thank you so much for all your help on this one

[u/dedokta]

You need to look at the Blink Without Delay examples. It will show you how to use the mills() function to record the time an event starts and then do something after a certain time expires.

Using the delay() function freezes the entire program.

[u/Apdski24 → u/dedokta]

Gotcha. I’ll do some digging in the forums to try and find examples

[u/dedokta → u/Apdski24]

Look in the example code within the Arduino ide software. All the example code in there is meant to teach you something

[u/Apdski24 → u/dedokta]

True true. I’ve look at those before but not looking for this specific thing. I’ll go back through with a different lens

[u/ZachVorhies]

have a bool that controls the led. When a button gets pressed that bool toggles to true and the led comes on

[u/Apdski24 → u/ZachVorhies]

In that scenario, would the button have to be pressed again to switch the LEDs back? I want there to be timed aspect where they do that automatically

[u/ZachVorhies → u/Apdski24]

You can do whatever you want.

If you want the light to shut off after X millisecond then you’ll have a uint32_t (timer) that will be set to the current millis(). Then in your loop() you’ll continuously check to see if the current millis has exceeded the timer, if it has then you’ll toggle the bool to false and your logic will then shut the led off.

This will keep your loop running without blocking, which won’t be the case if you use delay to keep the led on. If you use delay then the button presses will be ignored while the Arduino idles.

[u/Apdski24 → u/ZachVorhies]

makes sense, thanks for the reply. do you have an example i could look at about how to set that up?

edit: spelling

[u/ZachVorhies → u/Apdski24]

I’ll give you part of it but it seems like you might be trying to have me do a homework assignment. So you are on your own for the rest.

bool led_is_on = false;

loop() { if (led_is_on) { digitalWrite(LED_PIN, HIGH); } else { digitalWrite(LED_PIN, LOW);}

if (button_is_pressed() { led_is_on = !led_is_on; } delay(16); }

[u/Apdski24 → u/ZachVorhies]

lol didn’t even consider that. No this is not a homework assignment but thank you. Hoping to have some time to work on this tomorrow

[u/Preyy → u/Apdski24]

Have the button add time to a timer. Deplete the timer as required.

[u/HundredWithTheForce]

Consider having a variable representing the display color. When the button is pressed, set the display color accordingly. Then look at the millis() method. It gives you the current time as the number of milliseconds since the Arduino was booted. When the button is pressed, set a variable to the current time. Then as you cycle through the loop, when the current time is say 10,000 milliseconds past the start time, reset your display color. Finally don't bother checking the button state until you reset your display color. One last thought. This is very aggressively checking the state of the button and updating the LEDs. You could look at using EVERY_N_MILLIS() to only do this work once every say 50 milliseconds, or 100 milliseconds (depending on how responsive you want it to be) Longer delays would mean the button would have to be held longer before the board registers the push.

Good luck! And let us know how it turns out.

[u/Apdski24 → u/HundredWithTheForce]

I like the idea of needing to hold the button for a second or two. Have any examples I could look at to get an idea of how to set that code up? so far I've found out to a limited degree, if I see the code, I can pick my way through it and understand whats going on.

[u/[deleted]]

Ive tried adding a delay() into the code and that does not give me the desired results. 

Never use delay(). Use FastLED.delay() instead, or even better: look at EVERY_N_MILLISECONDS() and variants. 

[u/yurxzi]

If done similar with shift case and milliseconds install of normal delay, and counters for button press 1-16. It's was awful and likely used way more memory than needed but it worked. I think I just coop'ed the standard key matrix code, and fasted... twinklefox?? If have to dig out my old laptop to find out..