Heart rate measurement through optical sensors

Resting heart rate is an very important health parameter that is directly related to the soundness of human cardiovascular system. This project describes a digital method of measuring heart rate through fingertip. The blood volume inside the finger artery fluctuates with heartbeats. This fluctuation can be measured by transmitting an IR light through the finger. A portion of this light is reflected back. The amount of light reflected back depends upon the blood volume. This small change in the reflected light is amplified through proper signal conditioning circuit and converted into a pulse. Later, a PIC16F628A microcontroller is used to count the pulses at the output of the signal conditioner and display the heart rate on seven segment LEDs.

The signal conditioning circuit uses two operational amplifiers to build a two-stage active low-pass filter with a gain of about 10000, and a cut-off frequency close to 2.5 Hz.

Contact less tachometer using PIC16F628A

Introduction Tachometer is a device that gives you the information about the rotational speed of any shaft or disc. It usually measures the speed in revolutions per minute (RPM). Today we are going to make a simple tachometer that could measure the rotation speed of a disk without making any physical contact (that's why it is contact less) with the rotating object. The range of this tachometer is 0 - 9999 RPM and displays the RPM on a multiplexed 4-digit seven-segment display. Of course, we are going to do this project on our usual PIC16F628A development board. Infrared sensor Contact-less measurement of RPM will be achieved through an IR sensor. An IR diode will send a beam of infrared towards the rotating disc, and any reflected pulse will be received by a photo diode. The resistance of a photo diode drops drastically when exposed to infrared. An infrared is reflected by a white surface and absorbed by the dark ones. The test disc for this project is shown below. You can see

Experiment No. 2 : Push Button and Seven Segment Display Interface

In this experiment, we will program the PIC16F628A as an UP/DOWN Decade Counter. The count value will be displayed on a Seven-Segment Display and will be incremented/decremented by two push buttons on the board. Experimental Setup: The board has built in interface for a multiplexed 4-digit seven segment display (HS-5461AS2 from www.futurlec.com ).We will select only one digit by connecting a Digit Select pin to Vcc, as shown in figure below. A black jumper wire is used for this purpose. The seven segments will be driven through PORTB (already wired on the board). Connect Push Buttons (PB3 and PB4) to RA1 and RA0 female headers using jumper wires.

PIC16F628A Development Board

The development board we are going to make for our experimental microcontroller PIC16F628A will look like this. Here are the features it is going to have: Access to all I/O pins through female header pins 4 Push Buttons for Input 4 LEDs for Output An LCD Interface Port A 4-digit Seven-Segment Display Interface LCD Backlight Switch and Contrast Adjustment ICSP Programming (Very Important)

Experiments with PIC16F628A

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