Esp32 pwm not fully switching off

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1

I am using the ESP32 to dim LED's connected to a Meanwell PSU here.

The ESP32 is set up with a webserver and a slider.

I am making use of a transistor circuit to give a 10V PWM Output which inverts the output.

I am making use of the map() function to invert this again from 0 (off) to 255 (fully on).

Each time the slider reaches 0 it is suppose to switch off, but on the the scope I can see a small output causing the LED's to not fully switch off.

The sliderVal also outputs 1 when printed to console.

Any suggestions?

// Send a GET request to <ESP_IP>/slider?value=<inputMessage>
  server.on("/slider", HTTP_GET, [] (AsyncWebServerRequest *request) {
    String inputMessage;
    // GET input1 value on <ESP_IP>/slider?value=<inputMessage>
    if (request->hasParam(PARAM_INPUT)) {
      inputMessage = request->getParam(PARAM_INPUT)->value();
      sliderValue = inputMessage;
      
      int sliderVal = map((sliderValue.toInt()), 0, 255, 255, 0);
     ledcWrite(ledChannel, (sliderVal));
     Serial.print("SliderVal: ");
     Serial.println(sliderVal);
    }
    else {
      inputMessage = "No message sent";
    }
    Serial.println(inputMessage);
    request->send(200, "text/plain", "OK");
  });

IMG_6079.HEIC
IMG_6079.HEIC4032×3024 2.55 MB

2

None of the code presented shows the setup of the LEDC API; timer configuration and channel configuration. Would you agree that if there is an issue with the timer configuration then the configuration error would be garbage in to the applying of a PWM value?

ESP32 LEDC API.

3

Hi, setup code below:

const int output = 23;

String sliderValue = "0";

// setting PWM properties
const int freq = 100;
const int ledChannel = 0;
const int resolution = 8;

void setup(){
  // Serial port for debugging purposes
  Serial.begin(115200);
  
  // configure LED PWM functionalitites
  ledcSetup(ledChannel, freq, resolution);
  
  // attach the channel to the GPIO to be controlled
  ledcAttachPin(output, ledChannel);
  
  ledcWrite(ledChannel, sliderValue.toInt());

  // Connect to Wi-Fi
  WiFi.begin(ssid, password);
  while (WiFi.status() != WL_CONNECTED) {
    delay(1000);
    Serial.println("Connecting to WiFi..");
  }

  // Print ESP Local IP Address
  Serial.println(WiFi.localIP());

  // Route for root / web page
  server.on("/", HTTP_GET, [](AsyncWebServerRequest *request){
    request->send_P(200, "text/html", index_html, processor);
  });

  // Send a GET request to <ESP_IP>/slider?value=<inputMessage>
  server.on("/slider", HTTP_GET, [] (AsyncWebServerRequest *request) {
    String inputMessage;
    // GET input1 value on <ESP_IP>/slider?value=<inputMessage>
    if (request->hasParam(PARAM_INPUT)) {
      inputMessage = request->getParam(PARAM_INPUT)->value();
      sliderValue = inputMessage;
      
      int sliderVal = map((sliderValue.toInt()), 0, 255, 255, 0);

      ledcWrite(ledChannel, (sliderVal));
    }
    else {
      inputMessage = "No message sent";
    }
    Serial.println(inputMessage);
    request->send(200, "text/plain", "OK");
  });
  
  // Start server
  server.begin();
}
4

Why so low?

You should read the documentation from the link in post number 1.

5

I can not confirm your findings that the pwm output does not go to 0. Here is a test sketch which uses an interrupt on pin 21 to read the pwm pulse count output of pin 23.

Jumper pin 21 to pin 23 for this test.

I would verify that your mapping works at you intend. Perhaps use constrain.

const int output = 23;
const int input  = 21;

volatile uint32_t count;
uint32_t copyCount;
uint32_t lastRead;
uint32_t switchCount;

// setting PWM properties
String sliderValue = "0";
const int freq = 100;
const int ledChannel = 0;
const int resolution = 8;

//interrupt counter
void IRAM_ATTR isr() {
  count++;
}

void setup() {
  // Serial port for debugging purposes
  Serial.begin(115200);
  pinMode(input, INPUT_PULLDOWN);
  attachInterrupt(input, isr, RISING);

  // configure LED PWM functionalitites
  ledcSetup(ledChannel, freq, resolution);

  // attach the channel to the GPIO to be controlled
  ledcAttachPin(output, ledChannel);

  ledcWrite(ledChannel, sliderValue.toInt());
}


void loop() {
  ledcWrite(ledChannel, sliderValue.toInt());

  if (millis() - lastRead >= 1000) //read interrupt count every second
  {
    lastRead  += 1000;
    // disable interrupts,make copy of count,reenable interrupts
    noInterrupts();
    copyCount = count;
    count = 0;
    interrupts();
    Serial.println(copyCount);
    switchCount++;
  }
  
  if (switchCount == 5)
    sliderValue = "1";

  if (switchCount == 10)
  {
    sliderValue = "0";
    switchCount = 0;
  }
}

Output:

0
0
0
0
0
100
100
100
100
100
0
0
0
0
0
100
100
100
100
100
6

Me neither. It goes down to 0 fine for me.
Any chance of the cause of this behavior being on the client side? Perhaps the slider code doesn't allow the used variable to go down to 0?

7

Slider does not go down to 0. Solved it by using an if statement. Not ideal but it works.

8

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