Electrocardiograph & Heart Rate Monitor




Introduction: Electrocardiograph & Heart Rate Monitor

About: I have a degree in engineering physics. I like to make crazy scientific experiments.

This instructable shows you how to make an electrocardiograph and a heart rate monitor. It is intended to be a fun science project only. Of course, it should not serve as a medical purpose.

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) Instrumentation amplifier INA128
- (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
-  Breadboard
-  Jump wires
Resistors :
- (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
Capacitors :
- (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

Here is the schematic of the circuit and a suggestion of the breadboard implementation. The two electrodes will be plugged on pin 2 and 3 of the INA128. An additionnal reference electrode (an antistatic wrist placed on your right leg) will be plugged in ground. This configuration allows you to use unshielded cables.

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

Download the attached file on your computer, open it with the arduino IDE, plug your arduino, dowload the sketch and you're ready to go!

Step 4: Make the Electrodes

Firmly attach the two paper clips on the pair of denuded speaker wire. Cut pieces of aluminum paper and clip them in the paper clips. The result should look like the picture. You might also want to experiment to find a better design.
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!

Put the antistatic wrist around your right leg and connect it to the circuit ground. 

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!

123D Circuits Contest

Third Prize in the
123D Circuits Contest

4 People Made This Project!


  • Fix It! Contest

    Fix It! Contest
  • Creative Misuse Contest

    Creative Misuse Contest
  • Metalworking Contest

    Metalworking Contest

210 Discussions


3 months ago

Hi, I just wanted to ask, after the INA, why do you use that combination of capacitors and resistors in the V+ of the OA?

Is it a band pass filter? Low pass? I cannot understand it.


can we use any other ammplifier other than this instrumentational amplifier 1NA128 ???

if there is any alternative of this plz tell me??

also plz tell me alternative for diode 1N3064


7 months ago

Hello i want to ask you about the probes did you just used the wires?? or there is something else?
because the video is not clear 100% it doesn't show the probes
i will be pleazed if you answer me
thank you


8 months ago

Hello birdyberth,

I constructed the circuit by following whole steps. The led flashed, but lcd screen showed " <30 bpm You are dead ". I think that there is a problem on arduino code. Could you help me please ?


1 reply

No, it's because you're dead! :p Do you have a scope to check the signal? Does the LED flash at a constant heart rate interval? Check your electrode connection, the problem is generally there.

Why was the SB Freeduino used instead of other Arduino boards?

1 reply

Hahaha :) This is my first arduino board I purchased in my life (I think it was in 2011, I don't remember)... I'm still using it! (although I had to change the atmega chip once because I blew it with too a short circuit and also I broke the RX diode on it by accidentally dropping it in the snow while it was working) At that time, arduinos were hard to find in canadian shops and the freeduino was a great alternative, and fun to build too (because it was sold in a semi-kit). But yeah, any arduino board will do.


9 months ago

Hello again
i can't find the INA 128 and the diode :'( can i replace it?

3 replies

Yes, try to experiment with any other instrumentation amplifier and standard low-voltage low-current diode.

dude the circuit is up here, go to step 2, there is the schematic and the breadboard placement of components

I don't offer coaching on how to make this project, everything is up here, if you have specific questions put them here in the comments section.


1 year ago

is there any alternative for Diode 1N3064 and Instrumentation amplifier INA128

1 reply

yes pretty much any small diode and any low-cost instrumentation amplifier will work

Hi. Would u please send me the coding? Thank you

Dude everything is up here, if you have more specific questions I'll answer them.

hey there. i'm using the whole instructions provided in this blog. but get stucked in making connections for 7805. since the CKT diagram provided has its 7805's GND connected to battery's (-ve) terminal. while 7805's o/p pin goes to general GND of the CKT. its mean generally every element's GND has 5V supplied. but i think it shouldn't be. it might be the reason my CKT doesn;t respond.


1 reply

Yes I'm using the 7805 to get -5V relative to circuit ground, to form a dual power supply. The circuit is designed to work with 5V, 0V (GND) and -5V mainly because of the instrumentation amplifier.

can you use an electrode instead of the anti-static strip? As I am not picking any signal!


1 reply

Yes using an electrode might improve the signal because anti-static strip has a fair amount of impedance. It was just a quick and cheap way to make a grounding electrode.