Light bulb flashes and I don't know why?

Hey guys im making a small project with an arduino board that turns on and off a light based of soud and if the light is already on. But for some reason when i run the code, the lightbulb spazzes out flashing until reaching the end of the code. The code technically works, but i dont know why the light flashes like that. here is a short clip of what happens whn i run the code Shortclip. ive included the code as well. Thanks for your help!!

tic %start timer
max_samples = 100;
filter_size = 25;
threshold_value = 0.80;
close all;
tic %start timer
count=1;
while count<=max_samples
 sound_data(count) = readVoltage(a,'A2');
 time_data(count) = toc;
 count = count+1;
 
end
count2=1;
while count2<=(max_samples-filter_size)
 avg_sound = mean(sound_data(count2:count2+5)); 
 
 Light = readVoltage(a,'A0');
 
 if (Light<5)&&(avg_sound<threshold_value) %No light and minimal sound (keep Light off)
    writeDigitalPin(a,'D2',0)
 elseif (Light>=5)&&(avg_sound>threshold_value) %light on and sound (keep light on)
    writeDigitalPin(a,'D2',1)
 elseif (Light>=5)&&(avg_sound<threshold_value)% light on and no sound (turn light off)
    writeDigitalPin(a,'D2',0)
 elseif (Light<5)&&(avg_sound>threshold_value)% light off and sound on(turn light on)
    writeDigitalPin(a,'D2',1)
 end
 count2 = count2+1;
end

[Walter Roberson]

At the moment it is not clear to me that digital pins latch instead of pulsing.

[Yisroel Rosenberg]

What do you mean? What would be a solution?

[Walter Roberson]

Reading further I see that writedigitalpin does latch. However you should probably configure the pin to pullup

https://www.mathworks.com/help/supportpkg/arduinoio/ref/configurepin.html

https://www.arduino.cc/en/Reference.digitalWrite

[Yisroel Rosenberg]

this doesnt change anything. any other ideas

Answer 1

[Walter Roberson]

Could you remind us what A0, A2, and D2 are connected to?

Your code hints that D2 is connected to the input of an LED, controlling whether it is lit or not. And it hints that A0 is the current light level. And it hints that A2 is a microphone.

If so then each time you turn off the LED, then after a sensor sampling delay of unknown length, the light sensor reading will fall. You do not have any sample buffer, so you risk entering into an unstable state, where you turn on the light because it is off, and then you immediately turn it off because it is on.

 if (Light<5)&&(avg_sound<threshold_value) %No light and minimal sound (keep Light off)
    writeDigitalPin(a,'D2',0)

low light, low sound, turn the light off

 elseif (Light>=5)&&(avg_sound>threshold_value) %light on and sound (keep light on)
    writeDigitalPin(a,'D2',1)

high light, high sound, turn the light on

 elseif (Light>=5)&&(avg_sound<threshold_value)% light on and no sound (turn light off)
    writeDigitalPin(a,'D2',0)

high light, low sound, turn the light off

 elseif (Light<5)&&(avg_sound>threshold_value)% light off and sound on(turn light on)
    writeDigitalPin(a,'D2',1)

low light, high sound, turn the light on.

So each case where the sound is high you turn the light on, and each case where the sound is low, you turn the light off. The value you read from the sensor does not have an effect on the output.

[Yisroel Rosenberg]

yes A0 is a light sensor and A2 is a microphone . so how do you suggest i add a buffer? ive never done that before so i would appreciate the help

[Walter Roberson]

At the moment the current state of the light does not affect whether you turn it on or off. How do you want to change that?

Suppose your sample sound was all 0. Suppose the light starts off so you get a low light reading. Then shine a brief light on the sensor so the reading goes high. Should you turn on the light? If so then the reading will go high. Do you want that to be self-reinforcing, or should it time out based on the continued low sound?

[Yisroel Rosenberg]

well thats why i set a limit so that even if the avg sound is low it wont go off untill it reaches a threshold

[Yisroel Rosenberg]

so how do i change that to take into consideration the current light reading

[Walter Roberson]

Is there any situation where you want to turn on the light or leave the light on even though the sound is low?

Is there any case where you want to turn the light off or leave the light off when the sound is high?

If the answer to both of these is No, then your current output depends only on the sound and not on the light reading .

[Yisroel Rosenberg]

yes i do thats whats in the code

[Walter Roberson]

I worked you through the cases above and showed that at present you ignore the light value. Your output currently depends only on the sound.