Description
The Keyes-039 or KY039 Heart rate monitor consists of two things, an Infrared LED, and an Infrared Phototransistor. The IR LED should come on whenever the sensor has power and stay on (because it is infrared, you won’t be able to see that it is on, but if you look through your cell phone camera you will). The IR photo transistor causes the voltage to change on a “sensor” wire, and this should be connected to one of the Arduino’s analog pins.