Ir break beam ciruit

[mej7000]

I am aware of the ir Libraries, but it is overkill for my purpose and there seems to be some processing delay with the libraries that I need to avoid.

What I want is a simple and fast "ir break beam detection circuit" using the ESP32 and the Arduino IDE. I want to use VS1838B sensors, so require a 38KHz ir LED sender. I am using two ESP32's (one sender, one receiver) as they will eventually be physically separated (~5feet), but for now they are only about 12" apart.

I thought this would be relatively simple, but I am getting a constant HIGH from the Sensor Pin regardless of if the 38K modulated LED is on or off. I have tested the LED and Sensor using the TinySender/TinyReceiver sketches and they work (aside from missing some data because I am polling so rapidly), so hardware appears to be valid.

I PWM an LED at 38,000Hz freq. Tested the LED will a RED LED and it appears to be working correctly, although I have not tested the modulation with an oscilloscope.

I am looking for a LOW from the VS1838B when the LED is turned on, but I never get the LOW I am expecting. I would love to know what I am doing wrong...

//ESP32 SENDER,  the number of the LED pin
const int ledPin = 23;  

// setting PWM properties
const int freq = 38000;
const int ledChannel = 0;
const int resolution = 8;
int dutyCycle = 255;
 
void setup(){
  // configure LED PWM functionalitites
  ledcSetup(ledChannel, freq, resolution);
  
  // attach the channel to the GPIO to be controlled
  ledcAttachPin(ledPin, ledChannel);

  dutyCycle = 255;
  ledcWrite(ledChannel, dutyCycle);
}
 
void loop(){
}

//ESP32 RECEIVER,  the number of the Sensor pin
const int sensorPin = 23;  

void setup(){
  pinMode(sensorPin, INPUT);
}
 
void loop(){
  printf("sensorPin(%d): %d\n", sensorPin, digitalRead(sensorPin));  //only get a 1 as output
  delay(100);
}

[LarryD]

Always show us a good schematic of your proposed circuit. Show us a good image of your ‘actual’ wiring.
Give links to components.

---

[LarryD]

dutyCycle = 255;

Tell us what this does ?

[Railroader]

Trouble with a circuit but no schematics? How are You thinking? That helpers have crystal balls?

[mej7000]

@mej7000

ledcWrite

ledcWrite(channel, dutycycle)

This function accepts as arguments the channel that is generating the PWM signal, and the duty cycle.

[mej7000]

not a great image and the board had extraneous stuff on it, but the circuit is very straight forward:

LED + 470ohm Resistor, 3.3v, Ground PMW from Pin23

Sensor +/- and Sensor wire to Pin23, +decoupling capacitor on Vcc

[Idahowalker]

@mej7000

const int ledPin = 23; // 16 corresponds to GPIO16

How did you figure that 23=gpio_num_16?

A duty cycle of 255%, weird.

show an image of your project.

post a schematic.

[mej7000]

Obviously that is a comment left over from the original code. It does not affect the execution of the code. Don't let it confuse you.

255 is an 8 bit value representing full brightness

[bluejets]

@mej7000

I want is a simple and fast "ir break beam detection circuit" using the ESP32

First part contradicts the second part.

[mrburnette]

Similar project:

Infrared Sensor Tutorial for Arduino, ESP8266 and ESP32 (diyi0t.com)

Other potential hits:
"ESP32" + "VS1838B"+ "break-beam" detection Arduino example at DuckDuckGo

When working a project such as yours, I like to test everything out with "similar" code. Once I know the hardware is good, it is hackin' time.

[LarryD]

Looks like there is no connection to column 27

---

255 with an 8 bit PWM is solid 3v3, i.e. no pluses !

Change this to 127

[mej7000]

Thanks! This was really helpful. I'm still experimenting, but something like this seems to be working well.

void loop(){
  ledcWrite(ledChannel, 127);
  delay(40);
  ledcWrite(ledChannel, 0);
  delay(60);
}

[mej7000]

Thanks. Yes you are right, when I plugged it back in I missed the row... And your 127 was great advice. I found this to be working well so far.

void loop(){
  ledcWrite(ledChannel, 127);
  delay(40);
  ledcWrite(ledChannel, 0);
  delay(60);
}