• 1
    Setup hardware

    SonOff Pow / Th

    Any ESP8266 / ESP32 relay that can be flashed with Tasmota (or other suitable firmware, here I'm using Tasmota) and has at least one usable GPIO is fine, personally I prefer ones that have power measurement, like the Sonoff Pow family or Shelly PM devices.

    Details to be added.

  • 2
    Setup Tasmota

    By default Tasmota's "power" command directly controls the relay, but generally I'm more interested in controlling something like temperature than a relay so need to do something. I'd like to be able to set a target temperature and to easily change between at least two different preset temperatures.

    The "power" command is linked to a relay, which is also linked to a button in the UI so would be convenient to use a "relay" for controlling the temperature instead of a heater resistor. Luckily Tasmota doesn't really care if a relay assigned to a GPIO really exists so one can use an unused GPIO as a "virtual relay" that will follow the "power" command and have a button in the UI:

    To achieve this, lets first setup Tasmota with the device's template as usual, pick yours from here, and then add a "virtual relay" to an unused GPIO, here GPIO4 (Configuration->Configure Template):


    The real relay was originally set as "1", but to allow using the plain "power on" / "power off" commands to change between low and high temperatures I configured the original relay in GPIO12 as "2" and the new virtual relay as "1".

    To rename the buttons:

    webbutton1 Heat
webbutton2 Resistor
webbutton3 Hold

    That's all about the basic configuration, Rules to continue from there.

  • 3
    Tasmota rules

    The rule to rule them all:

    For every device:
Rule1
  ON system#boot DO Var1 %mem1% ENDON
  ON Tele-am2301#temperature<%var1% DO power2 on ENDON
  ON Tele-am2301#temperature>%var1%+1 DO power2 off ENDON
  ON power1#state=0 DO backlog Var1 %mem1%;RuleTimer 0 ENDON
  ON power1#state=1 DO backlog Var1 %mem2%;Ruletimer %mem3% ENDON
  ON Rules#Timer=1 DO power1 off ENDON

Customized for each room, here for non-living space:

backlog var1 2; mem1 2; mem2 18; mem3 10800; rule1 on
# var1 = initial thermostat value, degrees Celsius
# mem1 = lower thermostat value, degrees Celsius
# mem2 = higher thermostat value, degrees Celsius
# mem3 = high thermostat timeout, seconds
#   10800 = 3 hours as seconds, ESP32 builds also allow 3*60*60

Description:
Rule1
# Start the ruleset 1

ON system#boot DO Var1 %mem1%
# At boot copy the lower value from flash to RAM

ON Tele-am2301#temperature<%var1% DO power2 on ENDON
# When sensor (here am2301 that supports AM2302=DHT22) reports
# temperature lower than the target, turn the real relay on  

ON Tele-am2301#temperature>%var1%+1 DO power2 off ENDON
# When temperature more than target + 1, turn the real relay off

ON power1#state=0 DO backlog Var1 %mem1%;RuleTimer 0 ENDON
# When state of the virtual relay 1 changed to "off", use the low value as target
# and stop timer
 
ON power1#state=1 DO backlog Var1 %mem2%;Ruletimer %mem3% ENDON
# When virtual relay turned on, use the high value as target
# and start the timer with value from mem3

ON Rules#Timer=1 DO power1 off ENDON
# When timer run out, turn the virtual relay off

    The virtual relay, controllable by the commands "power off" and "power on" sets the target temperature from the flash-based variables mem1  and mem2.

    For controlling there are three commands:

    • power off - Set the thermostat to the low temperature
    • power on - Set the thermostat to the high temperature
    • var1 nn - Set the thermostat to nn degrees Celsius

    After setting the value with var1, changing state with power on|off will set it back to a preset temperature.

    Note that "power on" will time out after the desired period and change back to the off/low state, but setting a certain temperature with var1 doesn't time out with the current set of rules.