An electrocardiogram (ECG) is a graphical representation of the heart's bioelectrical activity during a cardiac cycle. It provides vital insights into a person’s health by displaying P, Q, R, S, and T waves in sinusoidal and periodic patterns. This project focuses on designing an ECG simulator that continuously generates typical ECG waveforms, eliminating the need for direct electrode-based readings. The simulator is implemented using an instrumentation amplifier and a Johnson counter (IC 4017) in Multisim software, ensuring accurate waveform generation. It serves as a reliable tool for testing ECG amplifiers, aiding in biomedical research and medical device development.
- Power Supplies: Fixed (+5V) & Dual (+/-15V)
- Function Generator
- Digital Storage Oscilloscope (DSO)
- CD4017 IC (Decade Counter)
- IC 741C (Operational Amplifier)
- 1N4148 Diodes (8 units)
- Capacitors: 1µF (3 units)
- Resistors: 10kΩ, 15kΩ, 22kΩ, 330kΩ, 1MΩ (11 units)
- Probes, Wires, and Breadboard
Before hardware construction, the ECG waveform was modeled in Multisim. The CD4017 Johnson counter was used to generate distinct waveform components:
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P Wave (First two clock cycles): Formed using an integrator circuit. The capacitor charges during Q0 and Q1, and discharges during Q2, shaping the waveform. Amplitude adjustments were made via a potentiometer.
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QRS Complex (Q3 output): Derived using a differentiator circuit, where subtraction of Q3 output helped in forming the sharp QRS peaks.
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T Wave (Q6 and Q7 outputs): Created using another integrator circuit, ensuring a gradual recovery phase.
These three waves were combined using a summing amplifier with unity gain to generate a complete ECG signal.
The complete Multisim simulation can be found in: ./ECG-Simulator.ms14
| ECG Component | Amplitude | Time Constant (RC) | Selected Values (C, R) |
|---|---|---|---|
| P Wave | 0.3V | 0.33s | 1µF, 330kΩ |
| QRS Complex | 1.2V | 0.015s | 1µF, 15kΩ |
| T Wave | 0.4V | 0.33s | 1µF, 330kΩ |
To generate a precise ECG waveform, the circuit utilized:
| 1. Square Wave Input A square waveform served as the base signal. |
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| 2. RC Integrator (Low-Pass Filter) Converted the square wave into a smoother triangular waveform. |
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| 3. RC Differentiator (High-Pass Filter) Converted square waves into sharp spikes, forming the QRS complex. |
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Therefore, the simulated ECG output:
The measured ECG signal time period:
The simulated circuit was then built and tested in a real-world environment using the same components. The circuit was assembled on a breadboard:
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4017 IC Setup:
- The 4017 decade counter was placed on the breadboard, with VCC connected to +12V.
- Grounded Reset (pin 13) and Inhibit (pin 15) ensured stable operation.
- A 10V, 12Hz square wave from the function generator served as the clock pulse.
- The counter output was tested to confirm that each pulse activated the expected pin sequentially.
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Waveform Generation:
- P Wave Circuit: Connected and adjusted for 1V amplitude.
- QRS Complex Circuit: Connected with a 1.9V amplitude differentiator.
- T Wave Circuit: Integrated and set to 1.1V amplitude.
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Summing Amplifier Integration:
- The P, QRS, and T wave outputs were combined via a summing amplifier (IC 741).
- Diodes ensured proper signal combination.
- The output was passed through a capacitor to stabilize the waveform.
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Final Analysis Using an Oscilloscope:
- The ECG signal was observed on a digital storage oscilloscope (DSO).
- Time/div scale: 0.5s | Volts/div scale: 0.5V.
The fully connected hardware circuit:
This project is licensed under the MIT License.
You are free to use, modify, and distribute this project for educational and research purposes, but proper credit must be given to the original author (Noora-Alhajeri).
© 2025 Noora-Alhajeri. All rights reserved.
Originally Developed: June 10, 2022
Uploaded to GitHub: 2025
For questions or collaboration, feel free to reach out:
📧 Email: n.s3eedalhajeri@gmail.com
🌐 LinkedIn: Noora-Alhajeri