Mydin-UseCase-Basic-Thermostat

Basic Thermostat

This project implements a basic temperature control system from a 3 modules MyDin made of:

• DINCASE-MB3PICO : controler based on Raspberry-Pi Pico
• DINCASE-2R-BP3MOD : 2 relays backplane
• TMP-DS18B20-WP : a DS18B20 OneWire temperature sensor.

The temperature sensor takes the room temperature and the heater is controled by the relay 1.

• LED 1 reflect the Rel 1 state (so heating state).
• LED 2 is lit while a FORCED forced is currently active
• LED 3 will blink once to acknowledge T° increase.
• LED 4 will blink once to acknowledge T° decrease.
• BUTTON 1 reverse (force) the current state of the relay.
  When the relay is ON then it switch it off.
  When the relay is OFF then is switch it on.
• BUTTON 2 cancel the forced state.
• BUTTON 3 will decrease the setpoint T° of 1 degree.
• BUTTON 4 will increase the setpoint T° of 1 degree.

Current temperature, setpoint temperature and relay state is displayed in the REPL session.

Hysteresis

A thermostat allows to define the target temperature called the setpoint (eg: 25°C) and use an hysteresis range (EG: 2.5°C) to avoids continuous state change around the target temperature.

With the hysteresis, the heater starts heating from 25-2.5 = 22.5°C and will stop heating when the temperature raised above 25+2.5 = 27.5°C. The temperature will slowly decrease and the heater will start again when temperature falls under 22.5°C.

Forced Mode

From the previous example here upper

Lets say the heater already reached 27.5°C and the heather stopped.

The temperature is now 25°C and you are already frozen... unfortunately the heater will not restart before the temperature falls under 22.5°C.

Pressing the Forced button will restart the heating process and the forced state will automatically disabling when the temperature is reached.

Remarks: forced state can also be used during a normal heating process to stop it. In such case, the forced state will get disabled when the lower temperature is reached.