When measuring the speed with opta, it gives randomly incorrect values

Official Hardware Opta
1

There is a protrusion on the electric motor housings. The sensor gives a signal when it sees this protrusion. I want to see the time of 1 revolution of the motor. The average motor speed is 100 rpm. I wrote the program as follows. I see an average value of 500ms. But it gives small values ​​from time to time. I thought it was a serial communication error, but it is not a communication error.
Why do you think it gives low values?

unsigned long newTime = 0;
unsigned long cycleTime = 0;
bool  risingedge1 = LOW;

void setup()
{
pinMode (LED_D0, OUTPUT); //Motor
pinMode (LED_D1, OUTPUT);
pinMode (LEDR, OUTPUT); //Active_Input
pinMode (LED_BUILTIN, OUTPUT); //PLC_Active
pinMode (D0, OUTPUT); //Motor
pinMode (A0, INPUT); //Stop_B normally closed contact button
pinMode (A1, INPUT); //Start_B
pinMode (A5, INPUT); //Sensor
Serial.begin(9600);
}

void loop()
{

digitalWrite (LED_BUILTIN, HIGH); // If the PLC is working, the green LED will light up.

if (!digitalRead(A0)==HIGH || digitalRead(A1)==HIGH || digitalRead(A5)==HIGH) // If any of the buttons are pressed, the red LED will light up.
{
digitalWrite (LEDR, HIGH);
}

if (!digitalRead(A0)==LOW && digitalRead(A1)==LOW && digitalRead(A5)==LOW) //If the hand is removed from the button, the red LED will turn off.
{
digitalWrite (LEDR, LOW);
}

if (digitalRead(A1)==HIGH )
{
digitalWrite (D0, HIGH);
digitalWrite (LED_D0, HIGH);
}

if (!digitalRead(A0)==HIGH)
{
digitalWrite (D0, LOW);
digitalWrite (LED_D0, LOW);
} 

if (digitalRead(D0)==HIGH && digitalRead(A5)==HIGH &&  risingedge1==LOW)
{
risingedge1=HIGH;
cycleTime=millis()-newTime;
Serial.println(cycleTime); 
newTime=millis();
}

if (digitalRead(A5)==LOW &&  risingedge1==HIGH)
{
 risingedge1=LOW;
}

}

serial communication output
525
583
592
598
591
592
584
584
581
575
575
574
579
577
579
591
594
61
528
590
582
583
63
515
575

2

Hi, try changing this to INPUT_PULLDOWN

3

Thanks, I'll try.

4

I solved the problem. The sensor was faulty and was giving parasitic voltage. I changed the sensor and it was fixed.

1 Like
5

Take care (as @steve9 said) of undetermined logic states, independently of faulty sensors. To attach the digital line to an convenient default logic level is a good practice. Anyway, the correct software implementation is:

good -> the use of interrupts
far better-> use the digital signal rising/falling edge to read&reset a MCU timer

Hope this helps.

6

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