The KY-039 uses adjacent infrared emitter and detector components to observe pulse-related changes in reflected light with suitable contact. It is an educational signal experiment, not a medical instrument.
Acquiring a signal
Shield ambient light, keep contact pressure repeatable, sample regularly, remove baseline drift, and filter noise. Signal amplitude varies strongly with motion, skin, placement, and module construction.
Estimating pulse
Detect peaks with an adaptive threshold and refractory period, then calculate beat intervals and average several cycles. Reject results when contact or signal quality is lost.
Limits
Do not use a KY-039 for diagnosis or oxygen measurement, and validate any research use against an appropriate reference.
Engineering review: verify the library version, module operating voltage, and the actual board pinout before wiring; visually similar breakout boards can differ.
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