Thermostat PI

[XSPA2474KW]

Hello,

is it possible to create a thermostat PI (e.g. MTN6212-04XX) with Wiser?
I don't mean to have an MTN6212-04XX in the installation and just to visualize through Wiser.

In fact, I need to replace the MTN6212-04XX with a script.

Thanks for your help!

[admin]

This might be helpful: https://openrb.com/example-pid-thermostat-with-lm2/

[XSPA2474KW]

In this link mentions that: There is a PID function already added by default in Logic Machine -> Scripts -> Tools menu.

I have Wiser and not Logic Machine and there isn't by default in Wiser.

[admin]

The example is somewhat outdated. You need to create a user library named pid and copy the code there.
Then load the library in your resident script:

Code:

-- init pid algorithm
if not p then
  require('user.pid')
  p = PID:init({
    current = '1/1/1',
    setpoint = '1/1/2',
    output = '1/1/3'
  })
end

-- run algorithm
p:run()

[XSPA2474KW]

I will check it.

Thanks for the help.

Appreciated.

[XSPA2474KW]

Can you please tell me what should I write to the residential script?

Thanks in advance.

[admin]

See my previous post. The code there is for the resident script. Set the script sleep interval to at least 10 seconds or more. This controls how often the algorithm runs. Change group addresses as needed.

[XSPA2474KW]

Hello

I have added in residential the following:

Code:

-- init pid algorithm
if not p then
  p = PID:init({
    current = '32/2/16',
    setpoint = '32/2/17',
    output = '32/2/18'
  })
end

-- run algorithm
p:run()

and in the user library the following

Code:

PID = {
  -- default params
  defaults = {
    -- invert algorithm, used for cooling
    inverted = false,
    -- minimum output value
    min = 0,
    -- maximum output value
    max = 100,
    -- proportional gain
    kp = 1,
    -- integral gain
    ki = 1,
    -- derivative gain
    kd = 1,
  }
}

-- PID init, returns new PID object
function PID:init(params)
  local n = setmetatable({}, { __index = PID })
  local k, v

  -- set user parameters
  n.params = params

  -- copy parameters that are set by user
  for k, v in pairs(PID.defaults) do
    if n.params[ k ] == nil then
      n.params[ k ] = v
    end
  end

  -- reverse gains in inverted mode
  if n.params.inverted then
    n.params.kp = -n.params.kp
    n.params.ki = -n.params.ki
    n.params.kd = -n.params.kd
  end

  return n
end

-- resets algorithm on init or a switch back from manual mode
function PID:reset()
  -- previous value
  self.previous = grp.getvalue(self.params.current)
  -- reset iterm
  self.iterm = 0
  -- last running time
  self.lasttime = os.time()

  -- clamp iterm
  self:clampiterm()
end

-- clamps iterm value
function PID:clampiterm()
  self.iterm = math.max(self.iterm, self.params.min)
  self.iterm = math.min(self.iterm, self.params.max)
end

-- clamp and set new output value
function PID:setoutput()
  local t, object, value

  self.output = math.max(self.output, self.params.min)
  self.output = math.min(self.output, self.params.max)

  value = math.floor(self.output)
  local t = type(self.params.output)

  -- write to output if object is set
  if t == 'string' or t == 'table' then
    if t == 'string' then
      self.params.output = { self.params.output }
    end

    for _, output in ipairs(self.params.output) do
      grp.write(output, value, dt.scale)
    end
  end
end

-- algorithm step, returns nil when disabled or no action is required, output value otherwise
function PID:run()
  local result

  -- get manual mode status
  local manual = self.params.manual and grp.getvalue(self.params.manual) or false

  -- in manual mode, do nothing
  if manual then
    self.running = false
  -- not in manual, check if reset is required after switching on
  elseif not self.running then
    self:reset()
    self.running = true
  end

  -- compute new value if not in manual mode
  if self.running then
    -- get time between previous and current call
    local now = os.time()
    self.deltatime = now - self.lasttime
    self.lasttime = now

    -- run if previous call was at least 1 second ago
    if self.deltatime > 0 then
      result = self:compute()
    end
  end

  return result
end

-- computes new output value
function PID:compute()
  local current, setpoint, deltasc, deltain, output

  -- get input values
  current = grp.getvalue(self.params.current)
  setpoint = grp.getvalue(self.params.setpoint)

  -- delta between setpoint and current
  deltasc = setpoint - current

  -- calculate new iterm
  self.iterm = self.iterm + self.params.ki * self.deltatime * deltasc
  self:clampiterm()

  -- delta between current and previous value
  deltain = current - self.previous

  -- calculate output value
  self.output = self.params.kp * deltasc + self.iterm
  self.output = self.output - self.params.kd / self.deltatime * deltain

  -- write to output
  self:setoutput()

  -- save previous value
  self.previous = current

  return self.output
end

but is not working.
I have also this error below in the "error log" window

User library PID:133: attempt to perform arithmetic on field 'previous' (a nil value)
stack traceback:
User library PID:133: in function 'compute'
User library PID:110: in function 'run'

[admin]

Check that 32/2/16 exists and has correct data type. Try restarting the script by performing disable/enable.