Run 2 different PID codes

[Qhergt]

I'd like to run 2 different servos each controlled by a different section of PID code. How do I do this?

[br3ttb]

create two pid classes (myPID1 & myPID2, say) and link them to separate output, input, and setpoint variables.

On Sun, May 5, 2019, 11:43 PM Qhergt notifications@github.com wrote:

I'd like to run 2 different servos each controlled by a different section of PID code. How do I do this?

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[Qhergt]

How would I do that?

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From: br3ttb notifications@github.com Sent: Monday, May 6, 2019 2:49:34 AM To: br3ttb/Arduino-PID-Library Cc: Qhergt; Author Subject: Re: [br3ttb/Arduino-PID-Library] Run 2 different PID codes (#92)

create two pid classes (myPID1 & myPID2, say) and link them to separate output, input, and setpoint variables.

On Sun, May 5, 2019, 11:43 PM Qhergt notifications@github.com wrote:

I'd like to run 2 different servos each controlled by a different section of PID code. How do I do this?

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[lackdaz]

Hey Brett,

I loved the PID articles you wrote and its really furthered my understanding on the subject. I tried it pushing it further by deploying the code to multiple pid instances. I thought this would be a good example for writing in OO so that the variables are a lot easier to manage for each of the instances, say if I'm looking to scale up to 4 pid instances I've got a heater/thermistor setup for each unit and I wrapped the instantiated object instances into a "Heater" class seen here:

Heater::Heater(
  int analog_read_pin,
  int analog_control_pin,
  int signal_pin) :
    _read_pin(analog_read_pin),
    _control_pin(analog_control_pin),
    _signal_pin(signal_pin),
    pwm_state(0),
    current_temp(0.0),
    pid_output(0),
    crit_temp(CRIT_TEMP),
    threshold_range(THRESHOLD_RANGE),
    thermistor(
      new SmoothThermistor(
        new NTC_Thermistor(
          analog_read_pin,
          REFERENCE_RESISTANCE,
          NOMINAL_RESISTANCE,
          NOMINAL_TEMPERATURE,
          B_VALUE
        ),
        SMOOTH_FACTOR
      )
    ),
    pid(
      new PID(
        &current_temp, 
        &pid_output, 
        &crit_temp, 
        30, 1.0, 1, P_ON_M, DIRECT
      )
    )
    {
      pinMode(_control_pin, OUTPUT);
      pinMode(_signal_pin, OUTPUT);
    }

Heater::~Heater() {
  delete pid;
}

void Heater::begin() {
  pid -> SetMode(AUTOMATIC);
  pid -> SetSampleTime(50);
  pid -> SetOutputLimits(0, get_byte(PWM_PERCENT_MAX));
  digitalWrite(_signal_pin, LOW);

}

double Heater::read_temp() {
  const double celsius = thermistor->readCelsius();
  // Output of information
  // Serial.print("Temp: ");
  // Serial.print(celsius);
  // Serial.println(" ºC, ");
  return celsius;
}

void Heater::auto_pid() {
  pid -> Compute();
  analogWrite(_control_pin, pid_output);
}
... more class methods

and created two heater instances like this:

Heater *heater1 = new Heater(PID1_READ, PID1_CONT);
Heater *heater2 = new Heater(PID2_READ, PID2_CONT);

  heater1 -> begin();
  heater1 -> update();
  heater1 -> auto_pid();
  heater2 -> begin();
  heater2 -> update();
  heater2 -> auto_pid();

  unsigned long now = millis();

  if (now - last_published > PUBLISH_INTERVAL) {
    Serial.print(heater1 -> current_temp);
    Serial.print(",");
    Serial.print(heater1 -> pid_output);
    Serial.print(",");
    Serial.print(heater2 -> current_temp);
    Serial.print(",");
    Serial.print(heater2 -> pid_output);
    Serial.print(",");
    Serial.println(heater1 -> crit_temp);
    last_published = now;
  }

where I have the data output plotted to the Arduino Serial Plotter to see the PID in real-time action.

The only problem is that only the second instance works. I still get thermistor input but pid_output is always zero. I tested each individually to ensure they are both working. But it seems like when I'm creating a new instance for heater2 it declares over the previous instance for heater1. Any clue what might be happening? I'm a novice at writing C++ OO code and would take any advice.

[lackdaz]

I fixed it, turns out I put the pid.begin in the loop and was constantly redefining the config parameters. For anyone looking to solve this OO style, the solution is above

[br3ttb]

I'll add, for anyone else reading, that my approach in situations like this is to serial.print the values of the internals as much as possible. This will usually point to a value that isn't as it should be, and you can work back from there.

On Sun, Aug 4, 2019, 5:25 AM Seth Loh notifications@github.com wrote:

I fixed it, turns out I put the pid.begin in the loop and was constantly redefining the config parameters. For anyone looking to solve this OO style, the solution is above

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