Picture of Electrocardiograph & Heart Rate Monitor
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

Picture of 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
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MimiK18 days ago

Thanks for the great tutorial! What is the output? (Trying to figure out the gain) Also do you know the specs of the filters? I am looking to adapt the system for use on small animals and need to figure out exactly what needs to be adapted, or if the system will work as you've designed it.

I can replace the other Diode 1N3064?? because I can not find it

p.s: could you publish the source file for the Fritzing project? I'm trying to re-create it from scratch, but for example I can't find some parts like the INA128 etc... thank you so much :)

Hi and thanks for this amazing tutorial :)

I will build this as soon as possible, I just would like to avoid buying an Oscilloscope and I was thinking about sending the values to the serial port so I can read them from my computer and maybe with a pretty simple Python application I could draw a graph instead of having it drawed by the oscilloscope. Do yoou think it's possible or not? In case is possible where do I read the values from? Thank you so much!

aliumujib1 month ago
hi, I'd like to make an electrocardiogram using a heart rate scanner (the types that read heart rate from finger tips) how do I go about it? could you help modify your project for that? my email is , whatsapp +2347045095095
ciarak3 months ago

Hi this is a great project.

I was wondering how I would add more electrodes if I wanted to.


birdyberth (author)  ciarak2 months ago


You could make a duplicate of the circuit for each electrode you want to add. You could use the same reference electrode by connecting all the negative inputs of the instrumentation amplifier together to one electrode, and the positive inputs would be the probing electrodes.

ctle3 months ago

hi there,

great project, i was wondering where you were able to pick up the supplies from? my local store did not carry some of the components such as the amplifier INA128

birdyberth (author)  ctle2 months ago

Hi, I got the INA128 on the internet, I think it was on ebay.

chaitanya11232 months ago

hello.. I have planned to take this circuit up for my college project..and that requires me to design the same circuits PCB layout. Hence, Could you send me the list of exact components used as I will use Eagle software to design the PCB. Also is it okay if I use medical electrodes instead of making the same with household materials. Please contact me as soon as you can on to answer these questions and any further doubts? Merci!

French -

bonjour .. j'ai prévu de prendre ce circuit pour mon collège project..and qui me demande de concevoir la même disposition des circuits de PCB. Par conséquent, Pourriez-vous m'envoyer la liste des composants exacts utilisés comme je vais utiliser le logiciel Eagle concevoir le PCB. Aussi est-il correct si j'utilise des électrodes médicales au lieu de faire la même chose avec des produits ménagers. S'il vous plaît me contacter dès que vous le pouvez sur de répondre à ces questions et d'autres doutes? Merci!

fred_dot_u3 months ago

A great instructable and one for which I have been searching at length. I have an Arduino experimenters kit and probably can knock this out if I collect the parts.

Has anyone constructed this device in PCB form? It would be great to have a simple box with the electrodes and perhaps the O-scope leads extending, to enable easy connection and monitoring. The reliability of a circuit board design means no jumpers to pull out by accident, of course.

Is anyone here handy with circuit routing? Etching a board is a simple matter with a Radio Shack kit or just "stuff on hand" in a lot of cases.

I see that sparkfun has the DSO nano v3 for US$100.00. The site text says the only difference is a metal case rather than plastic.

youss73 months ago

hello dear

can we use Ad620 instead of Ina 128? can u send me the project in french version plz Merci!

monicute5 months ago


This is a really great project, I am planning to do it this weekend.

Is there a problem if I change the inamp (INA128) to the (INA118)?

Merci :)

birdyberth (author)  monicute5 months ago

Désolé, je suis un peu en retard si tu voulais une réponse pour la fin de semaine... :)

Honestly, I don't see the difference between these two, they have the same pinout and after a very quick look, pretty much the same specs. In fact, at the origin I've chosen this model a bit arbitrarily :) It should work fine.

Pendant que j'y pense, si tu veux la version française de mon code, écris-moi!

Merci beaucoup :D

Oui!Je voudrais voir la version française de ton code.

Could you please email me? [] :)

monicute monicute5 months ago

I am programming this on C language, when I finished could you help me to corroborate it is correct please?

can this thing of yours be used to observe and monitor a frogs heart rate, m doing a project on how potassium , calcium and sodium ions effect the heart rate and i need to know if this would work. Email me if you could. Thanks for this great project

birdyberth (author)  assassino desigen5 months ago

Yes, it's possible. You'll have to experiment with electrodes's location & fixation, and maybe with the gain of the circuit.

colossus205 months ago

Hi birdyberth, I have successfully managed to get together a working version of the circuit displayed above, I manage to get a somewhat constant signal with the LED and the speaker (I didnt bother ith the display) however when I try to get the signal with an oscilloscope at the point where you suggest I cant get a waveform and it sorts out the output signal.

Could it be that if the oscilloscope is connected to the mains voltage it produces the circuit to short out?

birdyberth (author)  colossus205 months ago

It's probably linked to the impedance of the oscilloscope, as I'm using high resistance values in my circuit. Try to add a very high resistance in series with your probe.

Yuly6 months ago

no importa si en lugar de usar el INA128 lo fabrico de esta manera? sin usar los over voltage protection.....

birdyberth (author)  Yuly5 months ago

If I understand your question, you want to make your own instrumentation amplifier? It's possible. The hint is to use high precision resistors. Good luck!

heriss696 months ago

Is it possible to convert this into a pacemaker? Like with a few added steps?

birdyberth (author)  heriss696 months ago

If I were you I wouldn't try that.

gada8887 months ago

is it possible for me to replace the Diode 1N3064 with 1N4001

birdyberth (author)  gada8886 months ago

Yes, it's possible. Pretty much any ordinary diode will do the job.

atolat7 months ago

Could you please explain the pulse counting logic?

birdyberth (author)  atolat7 months ago

It's an edge trigger, so it activates the counter only if the pin has just changed its state and if the pin is high.

tal satti7 months ago

nice project and thanks for sharing , i just wanted to ask u, is it possible to place the electrodes around the leg ? because i want to integrate the heart rate sensor to my project which is also placed at the ankle

birdyberth (author)  tal satti7 months ago

Thank you! In this case, I'm afraid it would probably pick up more the leg muscles movements than the heart signal. Good luck!

fzunana7 months ago

Hi, excellent proyect! Do you think its possible to make it store data? or send an exam to a device like a cellphone, ipad, via bluetooth?? like this one

once again, great work!

birdyberth (author)  fzunana7 months ago

Thank you! Yes, it could store the heart rate on a SD card if you add an SD card shield on the arduino or send it through bluetooth if you add a bluetooth shield... If you want to send the complete signal, you will have to modify the circuit... I don't know how, but that should be feasible.

jessyratfink8 months ago

This is brilliant. Great work!

birdyberth (author)  jessyratfink8 months ago

Thank you!

Hi birdyberth is there any chance you can make this work without the LCD or the speaker? I have built it and attached the probes but I dont seem to get the LED flashing or any output in my oscilloscope

sinzu8 months ago

Nice project !

Do you think it could be possible to use a similar method to build an electromyography (EMG) system to record the activity of a muscle instead of the hearth ?

birdyberth (author)  sinzu8 months ago

Thank you! That is definitely a good idea and it was already in my list of future projects! I will work on it in a few months. You can also try it by yourself!

kurtee8 months ago

Great project!

Think about creating a front end program using processing instead of a separate oscilloscope !

The electrocardiograph could be displayed on your computer.

birdyberth (author)  kurtee8 months ago

Thank you! I'm more interested by electronics than programming, but if someone use my work to create that I will be happy!

javiforex8 months ago

Cordial saludo

amigo, desde colombia Bogota (dc), gran proyecto,



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