Rule for humidity sensor driven fan relay

[rhannink]

Hello,

I use a Sonoff TH16 with the THS-01 hum/temp sensor running Tasmota to control my bathroom fan.
I started with the rule:

Rule1 ON SI7021#Humidity>70 DO _Power 1 ENDON ON SI7021#Humidity<65 DO _Power 0 ENDON

But this is suffering from overshoot, after turning off the fan, the hum rises a bit starting the fan again.
I tried to solve this with turning of the rule for 5 minutes after turning the fan off:

Rule1
  ON SI7021#Humidity>75 DO _Power 1 ENDON 
  ON SI7021#Humidity<70 DO backlog _Power 0 ENDON rule1 0 ENDON RuleTimer1 300 ENDON
  ON Rules#Timer=1 DO rule1 1 ENDON
Rule1 1

But this also does not work right. Last attempt I tried:

Rule1
  ON system#boot DO var1 0 ENDON
  ON SI7021#Humidity>75 DO power1 1 ENDON
  ON SI7021#Humidity>=70 DO if (var1!=0) RuleTimer1 0; var1 0 endif BREAK
  ON SI7021#Humidity<70 DO if (var1!=1) RuleTimer1 300; var1 1 endif ENDON
  ON Rules#Timer=1 DO Power1 0 ENDON

But this is still not working reliable. Fan is not turning off at all or is turn on again quicly after turning off.

Does anyone have a good rulset for a humidity driven bathrrom fan relay?

Gr. Remco

[sfromis]

You have pretty bad syntax here:
ON SI7021#Humidity<70 DO backlog _Power 0 ENDON rule1 0 ENDON RuleTimer1 300 ENDON
Not even clear what those things after the first ENDON is supposed to do, but nothing the rules engine can process. If you are trying to deactivate and activate rule set number 1 from inside of the rule set itself, that can't work.

A possibly useful technique is to set a PulseTime, meaning that when it is powering on, it will by itself power off again after that interval (like 5 minutes), unless extended with a new power on, or explicitly powered off. You can also use the TimedPower command in a similar way, having the interval in the command instead of a persistent setting. Both are simpler to manage, instead of a logic with RuleTimer.

Setting a minimum on-time reduces the risk of the fan cycling on/off in an annoying way; probably better to let it run a bit longer than strictly needed. Simplest case is to have a single rule to turn it on, and no explicit turn-off step, as this is assumed to be when no longer having the level to turn on.