I have made a sketch which turns on a fan at a setted humidity value
and turns it off at a second setted value. Now i would like to keep it running for about
10 minutes if it gets under the setted value. I found something on google but i don't get it working in my sketch.
This is the sketch i'm using.
#include "DHT.h"
#define DHTPIN 2 // what pin we're connected to
#define fan 4
int maxHum = 60;
DHT dht;
void setup() {
pinMode(fan, OUTPUT);
Serial.begin(9600);
dht.setup(2); // data pin 2
}
void loop() {
// Wait a few seconds between measurements.
delay(2000);
// Reading temperature or humidity takes about 250 milliseconds!
// Sensor readings may also be up to 2 seconds 'old' (its a very slow sensor)
float h = dht.getHumidity();
// Read temperature as Celsius
float t = dht.getTemperature();
// Check if any reads failed and exit early (to try again).
if (isnan(h) || isnan(t)) {
Serial.println("Failed to read from DHT sensor!");
return;
}
if(h > maxHum ) {
digitalWrite(fan, HIGH);
} if(h < maxHum -2) {
digitalWrite(fan, LOW);
}
Serial.print("Humidity: ");
Serial.print(h);
Serial.print(" %\t");
Serial.print("Temperature: ");
Serial.print(t);
Serial.println(" *C ");
}
Save the millis() value at the time that the start action (turning on the fan) happens. Then, each time through loop(), check whether the required waiting period has elapsed by subtracting the start time from the millis() value now. If the period has elapsed then act accordingly (turn off the fan) If not, then go round loop() again.
#include "DHT.h"
/* Let's do this C++ style
#define DHTPIN 2 // what pin we're connected to
#define fan 4
*/
const byte DthPin = 2;
const byte FanPin = 4;
const unsigned int MaxHum = 60;
const unsigned long FanRunTime = 10 * 60 * 1000UL;
unsigned long fanOnTime;
DHT dht;
void setup() {
pinMode(FanPin, OUTPUT);
Serial.begin(9600);
dht.setup(DthPin); // data pin 2
}
void loop() {
// Wait a few seconds between measurements.
// NOTE: you probably want to do this wil millis as well ;)
delay(2000);
// Reading temperature or humidity takes about 250 milliseconds!
// Sensor readings may also be up to 2 seconds 'old' (its a very slow sensor)
float humidity = dht.getHumidity();
// Read temperature as Celsius
float temperature = dht.getTemperature();
// Check if any reads failed and exit early (to try again).
if (isnan(humidity) || isnan(temperature)) {
Serial.println("Failed to read from DHT sensor!");
return;
}
if(humidity > MaxHum ) {
digitalWrite(FanPin, HIGH);
//Let's watch the clock to see what time it is now
fanOnTime = millis();
}
Serial.print("Humidity: ");
Serial.print(h);
Serial.print(" %\t");
Serial.print("Temperature: ");
Serial.print(t);
Serial.println(" *C ");
//Now let's check if we need to turn off the fan
//We only do that when the fan is running
//And get the time difference by wathcing the clock again
if(digitalRead(FanPin) && millis() - fanOnTime >= FanRunTime){
digitalWrite(FanPin, LOW);
}
}
I thought i got this sketch up and running. I tried it on a breadboard and it seemed to work. Bit now if i use the sketch and the fan is switched on the fan won't go off somehow it keeps hanging.
if the humidity is greater than threshold, then turn the fan on if necessary and (unconditionally) make a note of the time
if the humidity is less than the threshold and the fan is not running, do nothing
If the humidity is less than the threshold AND the fan is running AND its been ten minutes since we last made note of the time, then turn the fan off.
You need to make a note of the time unconditionally, because if the humidity happens to peak again while the fan is in its 10-minute interval, you want to reset the 10-minute counter from that point.
to make a note of the time, put millis() in a [b]static[/b] variable.
To check if 10 minuts has elapsed, subtract the recorded time from millis() and check for >= 600000L
And when the fan "hangs", what does Serial monitor tell you? Because I have no idea where this simple sketch can fail...
You can even expand the output a bit
#include "DHT.h"
/* Let's do this C++ style
#define DHTPIN 2 // what pin we're connected to
#define fan 4
*/
const byte DthPin = 2;
const byte FanPin = 4;
const unsigned int MaxHum = 60;
const unsigned long FanRunTime = 10 * 60 * 1000UL;
unsigned long fanOnTime;
DHT dht;
void setup() {
pinMode(FanPin, OUTPUT);
Serial.begin(9600);
dht.setup(DthPin); // data pin 2
}
void loop() {
// Wait a few seconds between measurements.
// NOTE: you probably want to do this wil millis as well ;)
delay(2000);
// Reading temperature or humidity takes about 250 milliseconds!
// Sensor readings may also be up to 2 seconds 'old' (its a very slow sensor)
float humidity = dht.getHumidity();
// Read temperature as Celsius
float temperature = dht.getTemperature();
// Check if any reads failed and exit early (to try again).
if (isnan(humidity) || isnan(temperature)) {
Serial.println("Failed to read from DHT sensor!");
return;
}
if(humidity > MaxHum ) {
digitalWrite(FanPin, HIGH);
//Let's watch the clock to see what time it is now
fanOnTime = millis();
}
Serial.print("Humidity: ");
Serial.print(h);
Serial.print(" %\t");
Serial.print("Temperature: ");
Serial.print(t);
Serial.print(" *C\tFan: ");
Serial.print((digitalRead(FanPin) ? "on" : "off"));
Serial.print("\tfanRunTime: ");
Serial.print(FanRunTime);
Serial.print("\tMillis: ");
Serial.print(millis());
//Now let's check if we need to turn off the fan
//We only do that when the fan is running
//And get the time difference by wathcing the clock again
if(digitalRead(FanPin) && millis() - fanOnTime >= FanRunTime){
Serial.print(" Fan turned OFF!!");
digitalWrite(FanPin, LOW);
}
Serial.println();
}
