1. Chest-worn monitors typically detect your pulse via an electronic signal and sends the reading to your connected device.

2. Some monitors have bio-impedance sensors that detect your heart rate by sending small electrical signals through the skin and measuring tissue resistance to calculate heart beats per minute.

3. In this project, optical heart rate monitors were used, which send bright LEDs through the skin and then measure the amount of light that bounces back. Blood absorbs light, so variations in light that the sensors detect can be used to determine pulse rate.

4. Two types of photophlethysmography - Transmission and Reflection.Transmission: - Light emitted from the light emitting device is transmitted through any vascular region of the body like earlobe and received by the detector.Reflection: - Light emitted from the light emitting device is reflected by the regions.

5. Normal resting adult human heart rate ranges from 60-100bpm.Tachycardia-fast heart rate- >100bpmBradycardia-slow heart rate- <60bpmDuring sleep – low heart rates-40-50bpm

6. Search pulse oximetry in Wikipedia.org

Transmissive application mode:- A sensor device is placed on a thin part of the patient's body, usually a fingertip or earlobe, or in the case of an infant, across a foot. The device passes two wavelengths of light through the body part to a photodetector. It measures the changing absorbance at each of the wavelengths, allowing it to determine the absorbances due to the pulsing arterial blood alone, excluding venous blood, skin, bone, muscle, fat, and (in most cases) nail polish.

Reflectance pulse oximetry:- may be used as an alternative to transmissive pulse oximetery described above. This method does not require a thin section of the person's body and is therefore well suited to more universal application such as the feet, forehead and chest, but it also has some limitations.

Monitoring heart rate and cardiac cycle

Because the skin is so richly perfused, it is relatively easy to detect the pulsatile component of the cardiac cycle. The DC component of the signal is attributable to the bulk absorption of the skin tissue, while the AC component is directly attributable to variation in blood volume in the skin caused by the pressure pulse of the cardiac cycle.

The height of AC component of the photoplethysmogram is proportional to the pulse pressure, the difference between the systolic and diastolic pressure in the arteries. Ventricular tachycardia and ventricular fibrillation can also be detected.

ARM, originally Acorn RISC Machine. A RISC-based computer design approach means ARM processors require significantly fewer transistors. This approach reduces costs, heat and power use. Such reductions are desirable traits for light, portable, battery-powered devices—including smartphones, laptops, tablet and notepad computers, and other embedded systems. A simpler design facilitates more efficient multi-core CPUs and higher core counts at lower cost, providing improved energy efficiency for servers

Use of ARM7 over other microcontrollers:-

This generation introduced the Thumb 16-bit instruction set providing improved code density compared to previous designs

To improve compiled code-density, processors since the ARM7TDMI (released in 1994) have featured the Thumb instruction set, which have their own state. (The "T" in "TDMI" indicates the Thumb feature.) When in this state, the processor executes the Thumb instruction set, a compact 16-bit encoding for a subset of the ARM instruction set. Most of the Thumb instructions are directly mapped to normal ARM instructions. The space-saving comes from making some of the instruction operands implicit and limiting the number of possibilities compared to the ARM instructions executed in the ARM instruction set state.