Biomedical heart rate detector

HEART RATE DETECTOR,MONITER USING MICROCONTROLLER

we need 

1. 8051 microcontroller model is AT89s51

2.IR diode LTH1550-01 photo transistor pair

3.sevensegmen disply with 3 digit

we detect the heart rate from finger tip using ir reflection and displays on display

When the heart expands (diastole) the volume of blood inside the finger tip increases and when the heart contrcats (systole) the volume of blood inside the finger tip decreases. The resultant pulsing of blood volume inside the finger tip is directly proportional to the heart rate and if you could some how count the number of pulses in one minute, that’s the heart rate in beats per minute (bpm)

IR transmitter /receiver pair is placed in close contact to the finger tip. When the heart beats, the volume of blood cells under the sensor increases and this reflects more IR waves to sensor and .When there is no beat the intensity of the reflected beam decreases. The pulsating reflection is converted to a suitable current or voltage pulse by the sensor

program

ORG 000H                   // origin
MOV DPTR,#LUT              // moves starting address of LUT to DPTR
MOV P1,#00000000B          // sets P1 as output port
MOV P0,#00000000B          // sets P0 as output port
MAIN: MOV R6,#230D         // loads register R6 with 230D
      SETB P3.5            // sets P3.5 as input port
      MOV TMOD,#01100001B  // Sets Timer1 as Mode2 counter & Timer0 as Mode1 timer
      MOV TL1,#00000000B   // loads TL1 with initial value
      MOV TH1,#00000000B   // loads TH1 with initial value
      SETB TR1             // starts timer(counter) 1
BACK: MOV TH0,#00000000B   // loads initial value to TH0
      MOV TL0,#00000000B   // loads initial value to TL0
      SETB TR0             // starts timer 0
HERE: JNB TF0,HERE         // checks for Timer 0 roll over
      CLR TR0              // stops Timer0
      CLR TF0              // clears Timer Flag 0
      DJNZ R6,BACK
      CLR TR1              // stops Timer(counter)1
      CLR TF0              // clears Timer Flag 0
      CLR TF1              // clears Timer Flag 1
      ACALL DLOOP          // Calls subroutine DLOOP for displaying the count
      SJMP MAIN            // jumps back to the main loop
DLOOP: MOV R5,#252D
BACK1: MOV A,TL1           // loads the current count to the accumulator
       MOV B,#4D           // loads register B with 4D
       MUL AB              // Multiplies the TL1 count with 4
       MOV B,#100D         // loads register B with 100D
       DIV AB              // isolates first digit of the count
       SETB P1.0           // display driver transistor Q1 ON
       ACALL DISPLAY       // converts 1st digit to 7seg pattern
       MOV P0,A            // puts the pattern to port 0
       ACALL DELAY
       ACALL DELAY
       MOV A,B
       MOV B,#10D
       DIV AB              // isolates the second digit of the count
       CLR P1.0            // display driver transistor Q1 OFF
       SETB P1.1           // display driver transistor Q2 ON
       ACALL DISPLAY       // converts the 2nd digit to 7seg pattern
       MOV P0,A
       ACALL DELAY
       ACALL DELAY
       MOV A,B             // moves the last digit of the count to accumulator
       CLR P1.1            // display driver transistor Q2 OFF
       SETB P1.2           // display driver transistor Q3 ON
       ACALL DISPLAY       // converts 3rd digit to 7seg pattern
       MOV P0,A            // puts the pattern to port 0
       ACALL DELAY         // calls 1ms delay
       ACALL DELAY
       CLR P1.2
       DJNZ R5,BACK1       // repeats the subroutine DLOOP 100 times
       MOV P0,#11111111B
       RET

DELAY: MOV R7,#250D        // 1ms delay
 DEL1: DJNZ R7,DEL1
       RET

DISPLAY: MOVC A,@A+DPTR    // gets 7seg digit drive pattern for current value in A
         CPL A
         RET
LUT: DB 3FH                // LUT starts here
     DB 06H
     DB 5BH
     DB 4FH
     DB 66H
     DB 6DH
     DB 7DH
     DB 07H
     DB 7FH
     DB 6FH
END

How to use

When power is switched ON, the indicator LED D4 will glow an continues in that state. Now place your finger tip over the sensor and adjust preset R14 so that the LED D4 starts blinking. After you got the LED blinking, reset the power and wait for 15 seconds. The display will show your heart rate in beats per minute