Setting up a basic PID controller using a temperature sensor, and a power switch & PWM

Setup, Configuration and Use Beginners
1
  • Platform information:
    • Hardware: Raspberry Pi 4
    • OS: Openhabian
    • Java Runtime Environment: which java platform is used and what version
    • openHAB version: openHAB 4.3.2
  • Issue of the topic: Cant find a step by step guide for a simple PID rule

Hello!

I am new to openHAB and home automation in general.

I got some shelly power switches and esphome based temperature sensors.

After playing around with Modeling and Plots i would like to try out the PID controller
add on. My understanding from the documentation is that in order for the PID to work
i need to have a action that accepts more then just ON/OFF. The way to do that would
be with a PWM item.

I just couldnt find any example/tutorial on how to implement that.

Any suggestions and links are welcome. Im stuck for 2 days now and dont seem to get
any closer to even test the PID addon.

thanks for any feedback!

2

First of all: Welcome to the very best home-automation community.
Btw: Trying for 2 days is quite a lot. You can ask here earlier and the best way is to describe your goal in detail and what you already tried (e.g. paste your code (use code fences!) or a screenshot of your rule).
I currently don’t use PID or PWM controllers but this is how I think it should work:

  • Install the add-ons (I guess that’s done)
  • Create a rule
    – chose ID and label as you like
    – select PWM as your template
    – save (ignore the error)
  • click PWM-trigger and chose your parameters
  • click add action and select your actuator and save the rule

Repeat the same for the PID-rule and chose your PWM-item as the action item.

3

Hi Lohtek

welcome to the openHAB world of wonder where anything is possible. Just sometimes a bad idea.

Please give all the information you can you will get your best results.

EG- Using a shelly to control temp in reptile enclosure with epshome temp sensor.

Advise you will cook your reptile when something happens you don’t understand happens and the heater stays on. Use a store bought heating solution.

4

Hi!

Thanks for the nice welcome!

For now i just want to use a 40W lightbulb on a power switch & a Temperature sensor
in a shoe box to test the capabilities of the PID controller and my ability to configure it.

If i manage that i want to replace the thermostat in my small workshop with a openhab
based control solution.

What i did so far is:

Create all the necessary items and channels. That worked like a charm!
Put up nice plots on the Overviewpage. Also very intuitive and very nice to look at.

For my PID experiment i installed the PID Controller and the PWM Controller Add-ons.

Then i created a String item with the Tags Setpoint and Temperature and put a control widget on the overview page for easy access.

After that i created a heaterpwm rule. And last but not least the PID rule.

Since my last post i fixed some errors and the PID is now triggering the PWM and the lamp/heater goes on. it overshoots and the openhab rules page is not responsive. but thats just
tuning issues i asume.

I guess now comes the tuning part. ill come back when i have finished playing around with the pwm dutycycle and other parameters and the PID.

5

Hello again!

Had some time to continue playing with PID and PWM so here is an update.

created the following items:

type: Number, class: Setpoint, semantic property: temperature
testSetpoint - this is used as the target temperature

type: Number, class: Equipment_HVAC
PwmDutyCycleItem - this one gets the value from the PID and is used by the PWM controller

type: Number, class: Point
PIDpInspector - Name of the inspector Item for the current P-part
PIDiInspector - Name of the inspector Item for the current I-part
PIDdInspector - Name of the inspector Item for the current D-part
PIDeInspector - Name of the inspector Item for the current regulation difference (error)

created a rule PWM controller:

configuration: {}
triggers:
  - id: 8ce443da-d45a-4202-8558-e98b2f472189
    label: PWM Trigger
    configuration:
      dutycycleItem: PWMdutycycleItem
      minDutycycle: 0
      equateMinToZero: false
      deadManSwitch: 10000
      interval: 60
      maxDutycycle: 100
      equateMaxToHundred: true
    type: pwm.trigger
conditions: []
actions:
  - inputs: {}
    id: "1"
    configuration:
      command: ON
      itemName: shelly1pmminig33030f9ec8240__10101020_Power
    type: core.ItemCommandAction

created a rule PID controller:

configuration: {}
triggers:
  - id: 719fd807-bd8a-4907-9de3-7e6992e6a442
    label: PID Controller Trigger
    configuration:
      iInspector: PIDiInspector
      setpoint: testsetpoint
      kp: 1
      pInspector: PIDpInspector
      kdTimeConstant: 1
      dInspector: PIDdInspector
      integralMaxValue: 100
      input: Test_1_Temperature
      eInspector: PIDeInspector
      kd: 1
      integralMinValue: 0
      ki: 1
      loopTime: 1000
    type: pidcontroller.trigger
conditions: []
actions:
  - inputs: {}
    id: "1"
    configuration:
      itemName: PWMdutycycleItem
    type: core.ItemCommandAction

still not working properly. it switches on below testsetpoint, but does not switch off.
even if the PWMdutycycleItem is 0 or , and i dont know how this can be is -1.

but then again i only defined a ON in the PWM Rules as command.

any insights are welcome. but i am in no hurry and confident that i can figure this out within a month or something like that…

cheers

6

Hi Lohtek

I don´t use the PWM Controller only the PID controller, but i guess your interval: 60 is to big.

http://10.0.0.97:8080/addons/automation/automation-pwm#:~:text=Yes-,interval,Yes,-minDutyCycle

Start with 1 sec. and adjust while testing

7

Hi!

This was not the fault, just changes the “reaction time” to duty cycle changes.

Well, i still dont know why PWM does not switch of when dutycyle is 0, or and thats strange sometimes -1 or -2.

I think i can build a scheduled script that checks if dutycycle is 0 and switches
off the power to the lamp/heater. but thats a workaround, id rather find out
what i am missing here with the PWM. At least i think i have a PWM problem
since my PID sets the dutycyle as i want it to, except for the small negative values
which should not matter since the PWM rounds up evrything below 0 to zero.
At least thats what the documentation in the GUI says.

Any ideas anyone?

8

I just reviewed your PWM code and i think found the reason why it’s not working.

You defined a command in your item action but the command should be empty.

Pulse Width Modulation (PWM) Automation - Automation | openHAB.

9

BINGO!

Thanks, that was the problem.
i almost got it a few days ago, regarding the defining ON but not OFF.

case closed.

working pwm config:

configuration: {}
triggers:
  - id: 8ce443da-d45a-4202-8558-e98b2f472189
    label: PWM Trigger
    configuration:
      dutycycleItem: PWMdutycycleItem
      minDutycycle: 0
      equateMinToZero: true
      deadManSwitch: 10000
      interval: 60
      maxDutycycle: 100
      equateMaxToHundred: true
    type: pwm.trigger
conditions: []
actions:
  - inputs: {}
    id: "1"
    configuration:
      itemName: shelly1pmminig33030f9ec8240__10101020_Power
    type: core.ItemCommandAction