Generate number

Question

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.

• jsotola: 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
• Ulinnuha Luthfi: i just wanna generate random number, with range, maybe had another alternative sketch?
• JRobert: 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.
• Ulinnuha Luthfi: how to upvote? so i need to make variable utside the loop?

Answer 1

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);
}

• Michel Keijzers: @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.
• Juraj: @MichelKeijzers, your function returns only the last value. the function number() should simulate values returned from a sensor
• Michel Keijzers: @Juraj ... thanks ... I thought that was the intention, but I guess the question was not so clear. Upvoted!
• Michel Keijzers: @UlinnuhaLuthfi (I removed my answer, this answer should answer your question already.
• Ulinnuha Luthfi: sorry everyone, i just realize how to upvote