Heartbeat Pulse Train Circuit

Generate a clean pulse train voltage signal that pulses with your heartbeat.

1. AD623 Instrumental Amplifier (datasheet)
2. ECG Electrode Pads (Amazon)
3. TENs Replacement Lead (Amazon)
4. Aux Headphone to Screw Terminal (Amazon)
5. Standard ceramic resistors and capacitors
6. Breadboard
7. Digital Oscilloscope (i.e. DSO-X 2024A Oscilloscope by Agilent Technologies)

Build the circuit according to the schematic. Break down the circuit into three stages and individually unit test

1. Sensor: ECG pads > TENs leads > screw terminal > jumper cables
2. Use a multimeter to check continuity between the pads and the jumper cables
3. Signal conditioning: connect the instrumental amplifier and passive twin T filter to reduce power line noise
4. Use a voltage regulator to apply a 0.01V DC on the input pins of the AD623 to test the gain of 1000 at the output pins. Be careful not apply a large input voltage, otherwise you may cook chip!
5. Output: 10x oscilloscope probe
6. Connect the leads according to the image above.

The twin T filter is tuned to filter out 60Hz powerline noise. This frequency may be different depending on the power grid of your municipality!

Place the two ECG pads on your body to generate small voltage signal on the order of 1mV. This may take trial and error. I personally had the best results when I placed my leads under my heart area (near the nipple) and under the armpit. Also read Einthoven's Triangle.

During the demonstration, I have a hand on my pulse. For the first half of the video, I am vocalizing every heartbeat. During the second half, I vocalize every other heartbeat. The pulsing voltage signal can be seen on the oscilloscope display. Indeed, the video shows the voltage signal perturbed and in sync with each of my vocalized heartbeat.