The LED pin must be adjusted into the cycle of 1 ms
Led seem to be using the PNP transistor to electricity, LED pin must receive a lower voltage.
Commonly used system of air purifier
An infrared light-emitting diode and phototransistor, diagonal decorate allows it to dust in the air, the reflected light is detected
The sensor has a very low current consumption (maximum 20 ma, ma 11 typical), can carry up to 7 VDC sensor. The output is an analog voltage is proportional to the measured by the dust concentration, sensitivity of 0.5 V / 0.1 mg/m3

Technical Details

Size (LWH): 3.4 inches, 0.5 inches, 0.5 inches
Product Details
Product Dimensions: 3.4 x 0.5 x 0.5 inches
Shipping Weight: 0.02 pounds (View shipping rates and policies)
ASIN : B00GET4KR0