Abstract: This paper describes the planning of an easy, low-priced microcontroller based mostly vital heart rate measuring device with LCD output. Vital sign of the topic is measured from the finger mistreatment sensors and also the rate is then averaged and displayed on a text based mostly LCD.
Above image shows the block diagram of Low Cost Heartbeat Monitoring System. Basically, the device consists of an LED and an LDR. The transmitter-sensor pair is clipped on one of the fingers of the subject. The LED emits infrared light to the finger of the subject.
The LDR detects this light beam and measures the change of blood volume through the finger artery. This signal, which is in the form of pulses is then amplified and filtered suitably and is fed to a low-cost microcontroller for analysis and display. The microcontroller counts the number of pulses over a fixed time interval and thus obtains the heart rate of the subject. Several such readings are obtained over a known period of time and the results are averaged to give a more accurate reading of the heart rate.
The calculated heart rate is displayed on an LCD in beats-per-minute in the following format:
Rate = nnn bpm
Where nnn is an integer between 1 and 999.
The LCD of the center beat monitor shows the beat per minute. The device half consists of sensing parts, LDR(light dependent resistor) and LED (light emitting diode), a comparator module, a low pass filter. Heart beat is detected by the sensing parts and also the comparator produces associate amplified sq. wave output. The comparator output is given to an occasional pass filter and also the filter output is fed to 1 of the digital inputs of PIC 16F877a sort microcontroller. The microcontroller output ports drives the LCD.