“This Instructable documents how to create a simple heart rate monitor using Photoplethysmography with an IR phototransistor via transmissive absorption using the Arduino to process the pulsatile data and display live results via a TFT screen. To use the source code and create the necessary circuitry you will need a reasonable grasp of electronics, knowledge of the Arduino, a DMM and some patience. The design has been optimised to work with easily obtainable ‘off the shelf’ commercial parts and re-purposed household items and gives reasonable results.”