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I wanna make some sketch to generate number to represent sensor value, with range from high (900) to low (670), that number decrease with range between 1-10 and with some delay of switching number with range from 5-15 seconds:

    void setup() {
      Serial.begin(9600);
    }

    void number(){
      int sensor = 0;                  //sensor variable
      int a = random(0, 10);           //range subtraction sensor value
      int delay = random(5000, 15000); //range delay switching value
      for(sensor = 900; sensor >= 670; sensor -=a){ //iteration sensor value with range 670-900
        Serial.println(sensor);
        delay(delay);}
    }

    void loop() {
    number();
    }

with output:

  • 900 (delay 7 sec)
  • 894 (delay 3 sec)
  • 988 (delay 5 sec)
  • 979 (delay 9 sec)

The sketch above was work as well, but i still can't using variable "sensor" result after iteration "for" in void loop. I hope you can help me, thanks.

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4
  • upvote for well presented question ... this is a programming question, so the c++ tag is valid, but the other 4 tags are not valid ... it is not completely clear what you are asking, but that appears to be because of language difference Commented Jan 8, 2020 at 19:25
  • i just wanna generate random number, with range, maybe had another alternative sketch? Commented Jan 8, 2020 at 19:34
  • To use the for() loop iteration variable after the end of the loop, it has to be defined outside of the loop. Defining a variable in the loop is a convenience for when you only need it inside the loop. Commented Jan 8, 2020 at 20:31
  • how to upvote? so i need to make variable utside the loop? Commented Jan 8, 2020 at 20:50

1 Answer 1

Reset to default
2 
int sensor = 900;                 //variabel sensor

void setup() {
  Serial.begin(9600);
  while (!Serial);
  randomSeed(analogRead(A0));
}

int number() {
  int a = random(0, 10);          //range pengurang nilai sensor
  int d = random(500, 1500); //range delay perubahan nilai
  if (sensor < 670) {
    sensor = 900;
  }
  sensor -= a;
  delay(d);
  return sensor;
}

void loop() {
  int val = number();
  Serial.println(val);
}

I modified the delay for test.

randomSeed ensures different random values at every run

EDIT: a not blocking version which returns the same values for random interval:

int sensor = 900;                 //variabel sensor
unsigned long nextChangeMillis = 0;

void setup() {
  Serial.begin(9600);
  while (!Serial);
  randomSeed(analogRead(A0));
}

int number() {

  if (millis() < nextChangeMillis)
    return sensor;

  int a = random(0, 10);          //range pengurang nilai sensor
  int d = random(500, 1500); //range delay perubahan nilai
  if (sensor < 670) {
    sensor = 900;
  }
  sensor -= a;
  nextChangeMillis += d;
  return sensor;
}

void loop() {
  int val = number();
  Serial.println(val);
}
Improve this answer
12
  • @Juraj Why did you kind of copied my answer? Btw, you don't need to return sensor in number(), since it's a global variable anyway. Commented Jan 8, 2020 at 20:39
  • 1
    @MichelKeijzers, your function returns only the last value. the function number() should simulate values returned from a sensor Commented Jan 8, 2020 at 20:44
  • @Juraj ... thanks ... I thought that was the intention, but I guess the question was not so clear. Upvoted! Commented Jan 8, 2020 at 20:46
  • @UlinnuhaLuthfi (I removed my answer, this answer should answer your question already. Commented Jan 8, 2020 at 20:47
  • 1
    sorry everyone, i just realize how to upvote Commented Jan 8, 2020 at 21:03

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