PLEASE NOTE : To avoid any risk of electric shock, only use battery alimentation. Electrodes are theorically isolated from the circuit by the instrumentation amplifier, but play safe. I'm not responsible for any accident that may happen.
This is a simple design that fits on a single breadboard. You are free to experiment and to custom it for your needs.
Since it's my first Instructable and also since English is my second langage, don't hesitate to contact me if you find an error or if you want some clarifications about a section or another. I will be happy to edit my project for the better!
Step 1: List of Materials
- (1) Operational amplifier 741
- (1) Arduino Uno
- (1) 16x2 characters Liquid crystal display
- (1) Voltage regulator 7805
- (1) 8 ohms mini speaker
- (1) Brigth LED (I use a 10 mm one)
- (1) Diode 1N3064
- (2) 9V Batteries with connectors
- Jump wires
- (2) 100 ohms, 1/4W
- (1) 470 ohms, 1/4W
- (1) 1 kiloohms, 1/4W
- (2) 10 kiloohms, 1/4W
- (2) 100 kiloohms, 1/4W
- (1) 1 Megaohms, 1/4W
- (1) 10 nF
- (1) 47 nF
For the electrodes :
- About one meter of speaker wire
- Antistatic wrist strap
- Medical tape
- Aluminum paper
- (2) metallic paper clips
- Shower gel (a substitute for electrocardiogram gel)
Optional but recommended:
-Oscilloscope, for the electrocardiography part of the device
Step 2: Build the Circuit
The best signal is just after the low-pass filter (between the two 100kOmhs resistors). I suggest that you plug the oscilloscope probe at this point for demonstration, although you might want to check other points to see if everything is working properly.
Step 3: Download Code on the Arduino
Step 4: Make the Electrodes
When everything is ready, put some shower gel on the electrodes and use some medical tape in order to stick the result on your chest.
Step 5: Place Electrodes and Play!
Place the electrodes on your chest and play with them until you get a signal. It could take some time, as the electrical connection is fluctuating. Be patient!
Here is a demonstration of my electrocardiograph :
An interesting thing to do is to experiment with electrode location as you will get a different signal. Professional electrocardiographs use 10 electrodes to map the signal (see the 3rd picture). On the first picture you can see my average electrode placement. This configuration works well because I essentially pick up the ventricular spike that I use for frequency measurement.
Another effect that you can see is the noise caused by movements. The electrodes can pick up electric signals of your muscles. If you want a clean signal, stay still!
Here is the video I've made (in French, sorry!) for my YouTube channel! Enjoy!