To develop and service electrocardiogram (ECG) equipment, an artificial signal that mimics a real ECG is essential. Elektor presented this electrocardiogram simulator design in May 2000. As you'll see, this DIY project has various potential applications.

Editor's Note: The ECG simulator described in this article should be used only for testing and repair purposes. It must never be connected to any equipment that is at the same time connected to a patient. Neither the author nor Elektor assumes any responsibility for injury or damage that may result from the use of the ECG generator.

Electrocardiogram Simulator Circuit

By mimicking a real ECG, you can test and research without the need to take measurements from people, significantly reducing potential risks for test subjects. This electrocardiogram simulator generates such a signal, and thanks to its crystal-controlled accuracy, it can also be used for calibrating pulse rate displays.
 
ECG simulator circuit
An analog arbitrary signal generator using discrete components.
“A microcontroller system is normally used to generate the test signal in industrial ECG test equipment, which is consequently rather expensive. However, you will look in vain,” explains the designer, J. Holzhauer. “Only two standard logic ICs and a few passive components are used. IC1 is a 24-stage binary counter with an integrated oscillator and divider. With the indicated crystal frequency of 4,194,304 Hz, a 16-Hz square wave signal appears at the Q18 output (pin 10). Switch S1b picks up a second signal (2 Hz or 1 Hz). The 16-Hz signal clocks IC2, which is a decimal counter with ten outputs. The second signal is differentiated by the combination of C3 and R3. Needle-shaped pulses are present at pin 15 of the decimal counter (IC2), as indicated on the schematic diagram. These pulses reset the counter to zero at the appropriate times. The job of diode D2 is to block the negative portion of the pulses.”
 
ECG simulator
ECG simulator, an analog waveform generator.


A 9-V battery serves as the power source for this electrocardiogram simulator circuit, which consumes only about 2.5 mA, ensuring long battery life. Assembly is quick and easy, as the circuit can be put together in just a few minutes using the provided printed circuit board.
The ECG tester PCB
The ECG tester fits in a small plastic enclosure

The Original Project

The article, “ECG Simulator: An Analogue Waveform Generator,” was published in Elektor May 2000. The article will be free to download for the two weeks following the publication of this news item. Enjoy!
Editor's Note: This article was first published in a 2000 edition of ElektorMag. Some of the components, products (e.g., PCBs), and links may no longer be available. Nevertheless, we think the educational content remains valuable, and we hope it inspires you to start a new project.
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