电子DIY-简单好玩的心率测量仪

　　这个小东西简单而好玩，可以做为单片机入门的一个课业设计。

　　将你的食指轻轻地放在传感器上，就能看到LED指示灯随着你的心跳而闪动，15秒钟以后，还能在数码管上显示你当前的心率。

核心部分在传感器上，这里用的是一套红外对管。

人体指尖的动脉比较发达，当动脉血管随心脏周期性收缩与舒张时，血管中的血液容积也会发生变化。

这时红外接收探头便能采集到的相应的光脉冲信号，经过去噪和放大后送到单片机，进行运算处理，便得到了心率数据。

笔者虽然不是自动化专业毕业，但是对单片机和PLC都有相当深入的了解。笔者毕业后从事产品设计，开发的第一款产品就是基于16位的80C196单片机来作为硬件平台；之后也接受过西门子S5与S7PLC的培训，并在某特高压工程中采用S5PLC作为控制系统硬件并开发相应的工程软件，所以笔者自信能为楼主解惑答疑!

采集部分的原理图

运算与显示部分的原理图

单片机代码

/*
Project: Measuring heart rate through fingertip
Copyright @ Rajendra Bhatt
January 18, 2011
PIC16F628A at 4.0 MHz external clock, MCLR enabled
*/

sbit IR_Tx at RA3_bit;
sbit DD0_Set at RA2_bit;
sbit DD1_Set at RA1_bit;
sbit DD2_Set at RA0_bit;
sbit start at RB7_bit;
unsigned short j, DD0, DD1, DD2, DD3;
unsigned short pulserate, pulsecount;
unsigned int i;
//-------------- Function to Return mask for common anode 7-seg. display
unsigned short mask(unsigned short num) {
switch (num) {
case 0 : return 0xC0;
case 1 : return 0xF9;
case 2 : return 0xA4;
case 3 : return 0xB0;
case 4 : return 0x99;
case 5 : return 0x92;
case 6 : return 0x82;
case 7 : return 0xF8;
case 8 : return 0x80;
case 9 : return 0x90;
} //case end
}

void delay_debounce(){
Delay_ms(300);
}

void delay_refresh(){
Delay_ms(5);
}

void countpulse(){
IR_Tx = 1;
delay_debounce();
delay_debounce();
TMR0=0;
Delay_ms(15000); // Delay 1 Sec
IR_Tx = 0;
pulsecount = TMR0;
pulserate = pulsecount*4;
}

void display(){
DD0 = pulserate%10;
DD0 = mask(DD0);
DD1 = (pulserate/10)%10;
DD1 = mask(DD1);
DD2 = pulserate/100;
DD2 = mask(DD2);
for (i = 0; i<=180*j; i++) {
DD0_Set = 0;
DD1_Set = 1;
DD2_Set = 1;
PORTB = DD0;
delay_refresh();
DD0_Set = 1;
DD1_Set = 0;
DD2_Set = 1;
PORTB = DD1;
delay_refresh();
DD0_Set = 1;
DD1_Set = 1;
DD2_Set = 0;
PORTB = DD2;
delay_refresh();
}
DD2_Set = 1;
}

void main() {
CMCON = 0x07; // Disable Comparators
TRISA = 0b00110000; // RA4/T0CKI input, RA5 is I/P only
TRISB = 0b10000000; // RB7 input, rest output
OPTION_REG = 0b00101000; // Prescaler (1:1), TOCS =1 for counter mode
pulserate = 0;
j = 1;
display();
do {
if(!start){
delay_debounce();
countpulse();
j= 3;
display();
}
} while(1); // Infinite loop
}

HEX代码

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:00000001FF

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调光控制输出电路最终是要控制远近灯的切换。而单片机的工作电压一般是在5V甚至更低，电流也是毫安级别的，是无法直接驱动远近灯光的切换的。因此本系统采用继电器驱动作为功率驱动。具体的控制电路如图4所示。