65 lines
1.8 KiB
C++
65 lines
1.8 KiB
C++
/********************************************************
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* PID RelayOutput Example
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* Same as basic example, except that this time, the output
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* is going to a digital pin which (we presume) is controlling
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* a relay. the pid is designed to Output an analog value,
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* but the relay can only be On/Off.
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*
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* to connect them together we use "time proportioning
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* control" it's essentially a really slow version of PWM.
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* first we decide on a window size (5000mS say.) we then
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* set the pid to adjust its output between 0 and that window
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* size. lastly, we add some logic that translates the PID
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* output into "Relay On Time" with the remainder of the
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* window being "Relay Off Time"
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********************************************************/
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#include <PID_v1.h>
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#define PIN_INPUT 0
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#define RELAY_PIN 6
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//Define Variables we'll be connecting to
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double Setpoint, Input, Output;
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//Specify the links and initial tuning parameters
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double Kp=2, Ki=5, Kd=1;
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PID myPID(&Input, &Output, &Setpoint, Kp, Ki, Kd, DIRECT);
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int WindowSize = 5000;
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unsigned long windowStartTime;
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void setup()
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{
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windowStartTime = millis();
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//initialize the variables we're linked to
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Setpoint = 100;
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//tell the PID to range between 0 and the full window size
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myPID.SetOutputLimits(0, WindowSize);
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//turn the PID on
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myPID.SetMode(AUTOMATIC);
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}
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void loop()
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{
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Input = analogRead(PIN_INPUT);
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myPID.Compute();
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/************************************************
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* turn the output pin on/off based on pid output
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************************************************/
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if (millis() - windowStartTime > WindowSize)
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{ //time to shift the Relay Window
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windowStartTime += WindowSize;
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}
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if (Output < millis() - windowStartTime) digitalWrite(RELAY_PIN, HIGH);
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else digitalWrite(RELAY_PIN, LOW);
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}
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