Humidifier¶

Purpose¶

Adds moisture to the grow space air to raise relative humidity and lower VPD when the environment becomes too dry. Operates as the "lower" side of the VPD PID controller — counterpart to the exhaust fan.

Hardware¶

• Component: TBD (e.g. ultrasonic mist transducer in a water reservoir, or a consumer ultrasonic humidifier)
• Interface: GPIO relay (on/off)

Control Logic¶

• Triggered by: VPD too high or RH below minimum threshold
• Output: relay on → humidifier produces mist
• Controller: PID on VPD — see State Machines

Safety Guards¶

• Maximum on-time per cycle (prevents over-saturation)
• Internal water level for humidifier reservoir must be maintained separately
• Avoid misting directly onto plant canopy to reduce disease risk

Sources¶

• Kyle Gabriel: VPD Regulation