Question

我正在尝试使用霍尔效应传感器和Arduino Uno构建转速计。我正在使用Arduino软件，我编写了以下代码：

#include <LiquidCrystal.h>

int sensorPin = 2; // hall effect
float revs;
float rpm;
volatile byte rpmcount;
long previousmicros = 0;
long interval = 500000;
LiquidCrystal lcd(12, 11, 6, 5, 4, 3);


void setup() 
{
  // setup serial - diagnostics - port
  Serial.begin(115200);
  // setup pins
  pinMode(sensorPin, INPUT);
  // setup interrupt
  attachInterrupt(0, RPM, RISING);
}

void RPM()
{
  rpmcount++;
} 

void loop() 
{
  unsigned long currentmicros = micros();
  int sensorValue = digitalRead(sensorPin);        // sensor value is read
  if (currentmicros - previousmicros > interval)  
  {
    previousmicros = currentmicros;

    detachInterrupt(0);
    revs=10.0/rpmcount;
    rpm =600.0/revs;
    Serial.print("rpmcount : ");
    Serial.print(rpmcount);
    Serial.print("  rpm : ");
    Serial.println(rpm);
    lcd.clear();
    lcd.begin(16, 2);
    lcd.print("RPM = ");
    lcd.setCursor(6,0);
    lcd.print(rpm,0);
    rpmcount=0;
    attachInterrupt(0, RPM, RISING);
  }
}

这可以正常工作并测量RPM，但是该值始终是60的因数。如何更改此值以便更准确地测量RPM，比如说+ -5 RPM？我尝试使用我的revs和rpm公式，但收效甚微。

Answer 1

现在你有

rpm =60.0*rpmcount;

您必须在较长时间内存储计数并从中计算值（或更改循环的运行频率）

Answer 2

在ISR中，不计算增加计数，计算自上次ISR起火后经过的时间。

unsigned long someArray[2] = {0,0};
unsigned char rpmindex = 0;

void RPM_isr()
{
   rpmindex ^= 1;
   someArray[rpmindex] = micros();
} 

// And then in the main body

{
   // Disable interrupts
   // Copy someArray to a localArray
   // reEnable interrupts
   // Compute the interval between ISR fires
   unsigned long interval = abs(localArray[0] - localArray[1]);
   // Compute RPM
   unsigned int rpm = (60*1000000)/interval;
}

伪代码由您自己承担风险。

编辑：关于RPM计算的错误数学。

如何获得更准确的RPM值

2 个答案: