This Photo Transistor Light Sensor is an amazing device that can detect ambient light. Unlike an LED, when light hits the internal chip, it causes current to flow from the long pin to the short pin. It comes with a built - in optical filter (likely an IR filter), which can accurately simulate light levels just like the human eye. Connect the pin on the 'thicker' part of the sensor to 3 - 15VDC, and connect the thinner - part pin to ground through a ~1K - 10K series resistor. In the dark, there's hardly any current flowing through the sensor or resistor, and the analog voltage is close to ground. When light is near the sensor, the current through the resistor increases, raising the voltage. You can adjust the series resistor to get the voltage range you need and measure the analog voltage with a microcontroller. If you get no readings, try flipping the sensor. These sensors are RoHS - compliant replacements for CdS photocells.
Using this photo transistor light sensor is easy. First, connect the pin on the thicker part of the sensor to a power supply of 3 - 15VDC. Then, connect the thinner - part pin to ground through a resistor between 1K and 10K. This will help you measure the light levels. When it's dark, the current flowing through the sensor and resistor is very low, and the voltage is near zero. As light hits the sensor, the current through the resistor increases, and so does the voltage. You can adjust the resistor to get the voltage range that suits your needs. Use a microcontroller to measure the analog voltage. If you're not getting any readings, just turn the sensor around. Remember, this sensor is a RoHS - compliant alternative to CdS photocells. Keep it clean and avoid exposing it to extreme conditions to maintain its performance.
