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.
You will need the following parts;
- Arduino Mega 2560 (from SainSmart)
- 1 off old coat hanger as depicted in the picture in Step 2 : The Sensor
- 1 off 1.8 SPI 128x160 TFT Module. I got mine for £2.79 from ebay. Here; http://www.ebay.co.uk/itm/1-8-Serial-SPI-TFT-LCD-Module-Display-PCB-Adapter-Power-IC-SD-Socket-128x160-/381339124956?hash=item58c99544dc:g:mqcAA0SwjvvvsM13
- 2 off TL072 FET OpAmps
- 1 off T121 NPN Darlington Transistor
- 3 off 1N4148 diodes
- 1 off BZY88C 3v3 Zener diode
- 1 off BPW96B Phototransistor
- 1 off TSAL6400 940nm IR 5mm Led
- 1 off Ceramic 1uF capacitor
- 2 off 4.7uF Electrolytic capacitors
- 1 off 22pF Ceramic capacitor
- 1 off 22nF Ceramic capacitor
- 1 off 10nF Ceramic capacitor
- 1 off 50K 10 turn potentiometer
- 3 off 4K7 resistors
- 4 off 10R resistors
- 2 off 7R5 resistors
- 1 off 1M0 resistor
- 1 off 3K9 resistor
- 2 off 10K resistors
- 1 off 100K resistor
- 5 off 1K resistors
- 1 off 220R resistor
Other than the Arduino Mega 2560 (Genuino), coat hanger and the TFT display, I purchased all the parts from FARNELL in the UK.
WARNING : The details contained herein are for information only and should not be relied upon for accurate heart rate monitoring in a clinical or any other environment.