EKG with an Arduino Uno (ATmega328)

Wikipedia defines electrocardiography as a transthoracic (across the thorax or chest) interpretation of the electrical activity of the heart over a period of time, as detected by electrodes attached to the surface of the skin and recorded by a device external to the body. The recording produced by this noninvasive procedure is termed an electrocardiogram (ECG or EKG).

Recently, a Maker by the name of birdyberth designed an Arduino-based electrocardiograph and heart rate monitor. The open source project files, along with build details, were posted to Instructables.

“[This] is intended to be a fun science project only [so] it should not serve a medical purpose. To avoid any risk of electric shock, only use battery alimentation,” he explained. “Electrodes are theoretically isolated from the circuit by the instrumentation amplifier, but [better to] play [it] safe.”

Key projects components include an Atmel-based Arduino Uno (ATmega328), instrumentation amplifier, LCD, voltage regulator, mini speaker, bright LED, diodes, 9V batteries, breadboard, jump wires, resistors, capacitors, electrodes, speaker wired, antistatic wrist strap, medical tape, aluminum paper, paper clips, shower gel (substitute for electrocardiogram gel) and an oscilloscope (optional).

As you can see in the schematic above, the two electrodes link with pin 2 and 3 of the INA128. An additional reference electrode (an antistatic wrist placed on the right leg) is plugged in ground, a configuration that allows the use of unshielded cables.

“The best signal is just after the low-pass filter (between the two 100kOmhs resistors),” said birdyberth. “I suggest 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.”

Interested in learning more? You can check out HackADay’s coverage here and the official Instructables here.