"No I2C Devices Found"

Hi, I'm using a tsl2561 lux sensor with an Arduino Uno. I'm using the sensorapi script in the examples of the Adafruit tsl2561 library. However, my Arduino cannot find the sensor. So I tried a script to see if it is even detecting the I2C device, and it keeps returning, "No I2C devices found". I attached a picture of my circuit and the code.
A4 (SDA) --> to SDA pin on tsl2561 (Brown)
A5 (SCL) --> to SCL pin on tsl2561 (Gray)
GND --> GND pin on tsl2561 (Black)
5V --> Vcc pin on tsl2561 (Red)
(It looks like in the picture that the red wire is connected to 3.3 V but it is connected to 5)


#include <Wire.h>

void setup() 
{
  Wire.begin();
  Serial.begin(9600);
  while (!Serial); // Wait for Serial to be ready
  Serial.println("\nI2C Scanner");
}

void loop() 
{
  byte error, address;
  int nDevices;

  Serial.println("Scanning...");

  nDevices = 0;
  for (address = 1; address < 127; address++ ) 
  {
    Wire.beginTransmission(address);
    error = Wire.endTransmission();

    if (error == 0) 
    {
      Serial.print("I2C device found at address 0x");
      if (address < 16)
        Serial.print("0");
      Serial.print(address, HEX);
      Serial.println(" !");

      nDevices++;
    } 
    else if (error == 4) 
    {
      Serial.print("Unknown error at address 0x");
      if (address < 16)
        Serial.print("0");
      Serial.println(address, HEX);
    }
  }
  
  if (nDevices == 0)
    Serial.println("No I2C devices found\n");
  else
    Serial.println("done\n");

  delay(5000); // Wait 5 seconds for next scan
}

Try swapping SCL and SDA connections. If that does not solve it post a link to the technical information that gives a schematic.

Is that sensor soldered to its header, or have you just stuck the pins through the holes?

1 Like

Are you certain that is a 5 volt device?
All the ones I see online are 3.3 volt.

The pins are just stuck through the holes. Does that make a difference?
I've also used a VCNL4040 sensor, and it has a little LED in the corner that blinks green and I just stuck the pins through the holes.

Yes, it makes a difference. You will not get good consistent connections just sticking the pins through and hoping they work.

1 Like

That is like stepping between momma bear and her cub. Those are loose connections and can damage both the peripheral and your Arduino.

I soldered the connections and it worked! Thank you so much!

Give the solution to @van_der_decken for finding the problem

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