Humidity monitoring and control is in preliminary development stage.

DHT11/DHT21(AM2301)/DHT22 sensors

DHT sensor family uses proprietary onewire protocol. For maximum flexibility, we don’t allocate a dedidcated pin for it. Generic PINs that are used for actuators(cooling, heating, and etc.) can be used for DHTxx sensors. Once assigned, the humidity reading is then available.

DHT sensors also report temperature, and the temperature sensor is available after a PIN is assigned to the DHTxx sensor.

NOTE:

• The humidity sensor must be assigned to a slot numebr that is smaller than the temperature sensor of the humidity sensor.
• I don’t get stable readings from my DHT21 sensor. I had on in my fridge, and the reading changes dramatically when cooling. I couldn’t get readings when fermenting lager at 10C. Maybe some fine tuning is needed, or it is the nature of DHT21. Don’t trust the temperature reading of DHTxx sensor before verifying.
• I have to supply 5V to my DHT21/AM2301 sensor when the “line” is too long, like 1 meter(3 feet).

BME280 sensors

BME280 utilizes I2C for communication. No extra PINs are required. Howerver, I2C addresses of 0x77 and 0x76 are reserved for BME280, so if the LCD uses one of these addresses, it won’t be detected.

If BME280 is present, it should be detected when listing devices.

Humidity Control

Humidity control runs similar algorithm as temperature control. The parameters are currently predefined and can be changed only by modification of source code.. “Humidifer” and/or “Dehumidifer” must be set-up for humidity control.

Parameter	Usage	Default value
IdleLow	maximum difference before Humidifying starts	3%
IdleHigh	maximum difference before Dehumidifying starts	3%
HumidifyingTargetHigh	the minimum difference before stopping humidifying	5%
DehumidifyingTargetLow	the minimum difference before stopping dehumidifying	5%
MinimumHumidifyingRunningTime	Minimum humidifying running time	60 secs
MinimumHumidifyingIdleTime	Minimum humidifying Idle time	60 secs
MinimumDehumidifyingRunningTime	Minimum dehumidifying running time	300 secs
MinimumDehumidifyingIdleTime	Minimum dehumidifying idle time	300 secs
MinimumDeadTime	Minimum idle time between humidifying and defhumdifying	600 secs

Eg. for humdifying,

• humidifier is started when the current humidity is lower than (TargetHumidity - IdleLow)
• humidifier is stopped when the current humidity is higher than (TargetHumidity + HumidifyingTargetHight)

for dehumdifying,

• dehumidifier is started when the current humidity is higher than (TargetHumidity + IdleHigh)
• dehumidifier is stopped when the current humidity is lower than (TargetHumidity - DehumidifyingTargetLow)