It would help a lot if you could make me an example of using the PID_v1.h library (if you think it could work) with input value from a sensor , setpoint a variable ( ie. 25oC ) , and give output HIGH or LOW to my relay.
I can't come up with anything better than the library example code.
Replace the analogReading of A0 with the reading of the dht sensor. Change the pins and setpoints to meet your needs. Forget about setpoint adjustments, buttons, display, etc to get started. The basic example should work, and the only issue might be the relay active low or high.
/********************************************************
* PID RelayOutput Example
* Same as basic example, except that this time, the output
* is going to a digital pin which (we presume) is controlling
* a relay. the pid is designed to Output an analog value,
* but the relay can only be On/Off.
*
* to connect them together we use "time proportioning
* control" it's essentially a really slow version of PWM.
* first we decide on a window size (5000mS say.) we then
* set the pid to adjust its output between 0 and that window
* size. lastly, we add some logic that translates the PID
* output into "Relay On Time" with the remainder of the
* window being "Relay Off Time"
********************************************************/
#include <PID_v1.h>
#define PIN_INPUT 0
#define RELAY_PIN 6
//Define Variables we'll be connecting to
double Setpoint, Input, Output;
//Specify the links and initial tuning parameters
double Kp=2, Ki=5, Kd=1;
PID myPID(&Input, &Output, &Setpoint, Kp, Ki, Kd, DIRECT);
int WindowSize = 5000;
unsigned long windowStartTime;
void setup()
{
windowStartTime = millis();
//initialize the variables we're linked to
Setpoint = 100;
//tell the PID to range between 0 and the full window size
myPID.SetOutputLimits(0, WindowSize);
//turn the PID on
myPID.SetMode(AUTOMATIC);
}
void loop()
{
Input = analogRead(PIN_INPUT);
myPID.Compute();
/************************************************
* turn the output pin on/off based on pid output
************************************************/
if (millis() - windowStartTime > WindowSize)
{ //time to shift the Relay Window
windowStartTime += WindowSize;
}
if (Output < millis() - windowStartTime) digitalWrite(RELAY_PIN, HIGH);
else digitalWrite(RELAY_PIN, LOW);
}