Beginning the heart-rate sensor

The beginning: With not much background knowledge on sensors, I had to do some studying and research before I began.
It was exciting bringing back out soldering iron to put the pieces together! (These pictures were from day 1 + 2 from the christmas box!)
Understanding the ECG:

The ECG is separated into two intervals:

PR Interval: The PR Interval is the initial wave that is generated by an electrical impulse traveling from the right atrium to the left atrium. This impulse causes the chambers to depolarise, thus forcing the heart to contract and send oxygen into the ventricle. The left atrium is responsible for receiving newly oxygenated blood from the lungs into the ventricles.

QT Interval: It represents the time taken for ventricular depolarisation and depolarisation. The QT Interval is where things get really interesting. The QRS is a complex process that generates the signature “beep” in cardiac monitors. During QRS both ventricles begin to pump. The right ventricle begins to pump deoxygenated blood into the lungs through the left and right pulmonary arteries. The pulmonary arteries are blue in the diagram because they are carrying deoxygenated blood. They are still called arteries because arteries carry blood away the heart. Science, Again!