N.M.ELECTRONICS

Heartbeat monitor is a project, which is used to measure the heart beat of a human. Usually heart beat is measured in terms of number of beats per minute. But in the electronic world, no one needs to wait for a minute. Actually in this project we are going to measure the heart rate for some few seconds, and we have to convert this for a minute.

First the heart beat signal is sensed with the help of a microphone sensor. The microphone which we are going to use is s dynamic microphone. The microphone will convert the acoustic input signal in to the electrical signal. The electrical signal will be in the sinusoidal waveform of ac voltage in the range of 2 to 3mV. Then the signal is amplified with the help of amplifiers.

After amplification, the output will be a sinusoidal wave form of -12V to +12V. Then the signal will be given to a zero crossing detector. That will produce a square wave output of 0 and +12V. Then the square wave will be given to a switching transistor. The switching transistor will convert the square wave input into TTL logic pulses.

Then the input will be given to the microcontroller through any one of its input pin. Then by writing an assembly language program, we can calculate the number of pulses. At the same time we can calculate the number of pulses for 5 or 10 seconds by enabling the timer in the microcontroller.

Actually the microcontroller will count the input in the form of hexadecimal format. But we normally use decimal number format in our life. So we are going to convert the hexadecimal data into decimal data by the software. And then the converted data will be displayed in the display.

The display may be LCD or 7 segments LED. In the LED display we can display only numbers and in the LCD display we can display the numbers as well as the alphabets. The LCD display is available in many varieties. Few of them are single line 16 character, two line sixteen characters. The LED display is depends on the design we can have in our PCB. That can be starting from two numbers.

Incase of any fault occurs, that is if the heart beat goes below a particular level, it has to indicate through an audible alarm. Also it has to indicate the high level. It can give indication in two ways, one is audible and another one is display. If we are going for a LCD display we can go for both display and audible alarm.