Wireless Pulse Sensor

This pulse sensor is designed to be used for communication between man and machine, giving a robot the ability to react to the pulse rate of its human mentor. The digital output of the circuit makes it useful in other applications as well.

The sensor itself consists of an ordinary LDR (with a resistance when illuminated of 300 Ω and a dark resistance of around 10 MΩ) and a bright LED (D1). The LED must have an output of at least 1000 mcd as light from it must pass through the finger and illuminate the LDR.