Proving the Business Case for the Internet of Things

Everlight ambient sensor checks heart rate in wearables

Steve Rogerson
December 6, 2016

Taiwanese company Everlight Electronics has developed an ambient light sensor for heart rate signal detection in wearable electronics for the health and fitness industry.
The ALS-PD50-42C operates at 550nm and is said to have a low signal calculation failure rate and a high current efficiency.
With the increasing demand for health-awareness, more and more people manage their health and progress through their daily activities. Advanced technology plays an important role in the growing market for fitness and wellbeing. Currently, the company says, these sensors are the most innovative and convenient way to measure heart rates.
Based on the principle of PPG (photoplethysmogram), the heart rate signal is calculated according to the current changes in transmission and reflection between the green light LED and the sensor to detect the systolic and diastolic blood vessels. With a detection area of 8.1mm2, the signal strength of the ambient light sensor is strong and reliable.
This bigger than usual sensing area can also improve the capabilities in instances when there are signal interferences caused by people’s skin colour, tattoos and hair on the skin. This allows for accurate and reliable detection for the wearable heart rate technology. Ideally, this technology should benefit runners who rely on accurate wearable devices.
A current signal output of 0.8μA at a light current of 100 lux from a white LED (Vr = 5V) improves detection on capillaries resulting in overall accurate signal strength. The device's coating design reduces the interference from UV light below 400nm and infra-red light above 650nm, thereby decreasing the effect of strong sunlight from outdoor exercise to ensure accurate measurements.
It can be operated within a supply voltage from 0 to 5V in a temperature from -25 to +85ËšC. This device is rated to be RoHS compliant, Pb free and halogen-free.