An ambient light sensor from Everlight Electronics, the ALS-PD50-42C, operates at a 550nm and has a very low signal calculation failure rate and a high current efficiency for heart rate signal detection in wearable electronics.

Based on the principle of PPG (photoplethysmogram), the heart rate signal is calculated according to the current changes in transmission and reflection between a green light LED and the light sensor to detect the systolic and diastolic blood vessels. With a large detection area of 8.1mm2, the ALS-PD50-42C's signal is strong and reliable, unaffected by signal interferences caused by people’s skin colour, tattoos and hair on the skin.

The ALS-PD50-42C series has a current signal output of 0.8μA at a light current of 100 Lux from a white LED (Vr = 5V). The device's coating design effectively reduces the interference from UV light below 400nm and infrared light above 650nm, thereby decreasing the effect of strong sunlight. The ALS can be operated within a supply voltage range from 0 to 5V in a temperature range from -25°C up to 85°C.

The device is rated to be RoHS compliant, Pb-free and halogen-free.