LED dimming using analogeWrite and MIT app inventor

[JATT]

Hi This is my first time using Arduino for a school project. I am working on dimming a LED panel using PWM pins on Arduino Uno and I have a problem in my code. I was able to dim it using analogWrite(light, 127) automatically. However what I want is to dim it using an App that was created using MIT app inventor.

The app has 4 buttons (100%, 75%, 50%, and 25%) for each I want to use (analogWrite(light, 255), analogWrite(light, 191), analogWrite(light, 127), analogWrite(light, 64)) respectively. When I used an if statement the analogWrite didn't function and when I tried digitalWrite it worked but its only setting it high or low. The app is sending a text "1" or "2" "3" and so on to the bluetooth module HC-06.

Is there a way I can use analogWrite for these four stages? and can you please explain how or walk through the steps.

Thank you in advance

I have attached the Arduino code it is very simple and the MIT app code

[INTP]

I don't see any if statements. What LED panel?

[JATT]

I am using a LED panel from China but Im testing it first on a small led.

This is the code:

int light = 9;

void setup() {

Serial.begin(9600);
pinMode(light, OUTPUT);

}

void loop() {

if(Serial.available() > 2)
{
int received = Serial.read();
Serial.println (received);

if (received == 1 )
{
analogWrite(light, 255);
}

else if (received == 2)
{
analogWrite(light, 191);
}

else if (received == 3)
{
analogWrite(light, 127);
}

else if (received == 4)
{
analogWrite(light, 64);
}
}

[INTP]

Is the printing showing you the signals you are expecting?

[LarryD]

Why > 2

Do you know what ASCII is?

[JATT]

From the serial monitor I am getting (49,50,51,52) for buttons (100%, 75%, 50% and 25%)and nothing is working

[INTP]

JATT:
From the serial monitor I am getting (49,50,51,52) for buttons (100%, 75%, 50% and 25%)and nothing is working

Yeah, there's a secret cipher called ASCII where 49 = 1, 50 = 2, 51 = 3, and 52 = 4.

If you changed 'if received == 1' to == 49, it'd work.

Or you can throw in some ' marks around '1' and such. Chars are different from values.

[JATT]

not sure, is it supposed to be greater than 0?

[JATT]

Many thanks for your reply it is working now but there is a problem

When pressing 100% I get full brightness

Wehn I press 75% it takes 3 times to go to the next level of brightness
and same thing happens when I press 50% 3 times

From serial monitor:

52
52
49

49
49
50

50
50
51

I am wondering if this is a delay problem

[LarryD]

if(Serial.available() > 2)
Change to:
if(Serial.available() > 0)

[JATT]

Got it thanks

I still have a problem when I press any button it takes 3 times to go to the next level of brightness any idea why its happening

From serial monitor:

52
52
49

49
49
50

50
50
51

[system]

Can you post your code?

[JATT]

Here is the code

int light = 9;

void setup() {

Serial.begin(9600);
pinMode(light, OUTPUT);

}

void loop() {

if(Serial.available() > 0)
{
int received = Serial.read();
Serial.println (received);

if (received == 49)
{
analogWrite(light, 64);
}

else if (received == 50)
{
analogWrite(light, 127);
}

else if (received == 51)
{
analogWrite(light, 191);
}

else if (received == 52)
{
analogWrite(light, 255);
}
}
}

[system]

I can't see any reason that you should have to enter a character more than once.
Are you sure that is the code you have uploaded?

  int received = Serial.read();
  Serial.println (received);
 
  if (received == '1')

etc makes things easier to read.

[MarkT]

If its taking 3 presses you've still got the available > 2 version uploaded.

Check the compile/upload succeeds every time you compile/upload by looking at the warnings/error window at
the bottom of the sketch pane - uploads can and do fail, and if in doubt upload again.

[JATT]

Yea I had the > 2 version uploaded instead but now its working thank you guys for your help

I am now working on adding an increase and decrease button to increase the brightness by 10% or 5% every time the button is being clicked.

Any idea on how to add that to the code or useful resources that I can look at cause I want it to increase/decrease depending on if someone previously clicked on the 25%-50%-75%-100% button.

I tried increasing it by adding almost 12.7 (10%) to the value and manually put that in the code but I want it with an if statement so that I can use the app hopefully thats clear

I would appreciate any idea

analogWrite(light, 256);
delay(2000);

analogWrite(light, 241);
delay(2000);

analogWrite(light, 229);
delay(2000);

analogWrite(light, 216);
delay(2000);

analogWrite(light, 203);
delay(2000);

analogWrite(light, 191);
delay(2000);

analogWrite(light, 178);
delay(2000);

analogWrite(light, 165);
delay(2000);

analogWrite(light, 152);
delay(2000);

analogWrite(light, 140);
delay(2000);

analogWrite(light, 127);
delay(2000);

[CrossRoads]

analogWrite(light, 256);
delay(2000);

analogWrite only works with 0 to 255

256 might wrap around to 1.

[JATT]

I added the increase decrease however I noticed two issues:

One;

when I connected the oscilloscope to the circuit and pressed High button (75% duty cycle) I am getting a flipped signal same as when I press Low button (25% duty cycle). I used a npn transistor (PN2222) the base to 1K to Arduino pin 9, emitter to ground, and collector to Dim+ of panel and Dim- to ground of Arduino.

I am not sure why its flipped or if its supposed to be like that?

I attached a screenshot of the scope when pressing High button.

int panel1 = 9;
int x = 0;
int y = 0;

void setup() {
          
            Serial.begin(9600);
            pinMode(panel1, OUTPUT);
              
          }
          
          void loop() {
          
             if(Serial.available() > 0)
             {
              int received = Serial.read();
              Serial.println (received);
             
                  if (received == '1')          // if High is clicked 
                  {
                    analogWrite(panel1, 191);  // 75% duty cycle 
                    x = 191;
                    y = 191;
                  }
                
                  else if (received == '2')     // if Med is clicked 
                  {
                    analogWrite(panel1, 127);  // 50% duty cycle
                    x = 127;
                    y = 127;
                  }
                
                  else if (received == '3')     // if Low is clicked
                  {
                    analogWrite(panel1, 64);   // 25% duty cycle 
                    x = 64;
                    y = 64;
                  }
                
                  if (received == '4')         // if increase is clicked 
                  {
                    int newx = x - 13;
                    analogWrite(panel1, newx);
                    x = newx;
                    if (newx <= 217)
                    {
                      x = 271;
                    }
                    }
                  }
                  if (received == '5')
                  {
                    int newy = y + 13;
                    analogWrite(panel1, newy);
                    y = newy;
                    if (newy >= 38)
                    {
                      y = 38
                    }
                  }
                 }
}

[LarryD]

If you look at pin 9 you will see the inverse what’s on the collector of the 2N2222.

[JATT]

I didn't really get what you meant

the probe of the scope is connected to the base of npn that is connected to pin 9 and the ground are you saying that I should connect it to the collector instead