user10894: urgently need some inputs,
Connection:
VCC-5v
GND-GND
SCL-SCL(analog pin 5)
SDA-SDA(analog pin 4)
ADD-NC or GND

Code pasted below
used library from GIT : https://github.com/claws/BH1750
#include <BH1750.h>
#include <Wire.h>

BH1750 lightMeter;

void setup(){
    Serial.begin(9600);
    lightMeter.begin();
    Serial.println("Running...");
}

void loop() {
    uint16_t lux = lightMeter.readLightLevel();
    Serial.print("Light: ");
    Serial.print(lux);
    Serial.println(" lx");
    delay(1000);
}


user10394: There may be a regulator and logic shifter on the board you are using but according to the data sheet the device is a 3V device with 1.8V logic and I2C levels.  So this is the first thing you need to check.
Have you got 4.7K resistors pulling the SDA and SCL lines to Vcc? 
Can you change your code to turn the device off and then take a reading?
There is nothing wrong with your code, your wiring looks OK, so that implies that there is something wrong with the device or the Arduino.  Change the device (and code) for another I2C device and see if that works fine.  If it does then it looks like there might be a problem with the BH1750.
Hope that helps.

10894: <p>urgently need some inputs,</p>

<p>Connection:</p>

<pre><code>VCC-5v
GND-GND
SCL-SCL(analog pin 5)
SDA-SDA(analog pin 4)
ADD-NC or GND
</code></pre>

<p>Code pasted below
used library from GIT : <a href="https://github.com/claws/BH1750" rel="nofollow">https://github.com/claws/BH1750</a></p>

<pre><code>#include &lt;BH1750.h&gt;
#include &lt;Wire.h&gt;

BH1750 lightMeter;

void setup(){
    Serial.begin(9600);
    lightMeter.begin();
    Serial.println("Running...");
}

void loop() {
    uint16_t lux = lightMeter.readLightLevel();
    Serial.print("Light: ");
    Serial.print(lux);
    Serial.println(" lx");
    delay(1000);
}
</code></pre>
 10394: <p>There may be a regulator and logic shifter on the board you are using but according to the data sheet the device is a 3V device with 1.8V logic and I2C levels.  So this is the first thing you need to check.</p>

<p>Have you got 4.7K resistors pulling the SDA and SCL lines to Vcc? </p>

<p>Can you change your code to turn the device off and then take a reading?</p>

<p>There is nothing wrong with your code, your wiring looks OK, so that implies that there is something wrong with the device or the Arduino.  Change the device (and code) for another I2C device and see if that works fine.  If it does then it looks like there might be a problem with the BH1750.</p>

<p>Hope that helps.</p>
