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hardware:venta_connected

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Adding WiFi-control to a Venta LW45 humidifier

Why adding WiFi to a traditional humidifier

In our appartment, we have used a Venta LW45 air humidifier during the winter to increase air humidity to acceptable levels. These humidifiers follow a very simple principle: A ventilator blows air through the device, while several rotating discs are placed in the water and provide enough water to the airflow through them. The humidifier has three operating levels (1-3) and signals an error if the water reaches a low level.

Now, since I have ZigBee temperatur and humidity sensors in every room, I wanted to automate the humidifier and write rules in OpenHAB that would turn on the humidifier whenever the humidity falls below a threshold and also turn it off again once an acceptable level is reached.

Investigating the electronics of the LW45

Previous versions of the Venta humidifier (LW14, LW24, LW44) are simply using a 220V motor with a manual switch that changes between different resistor values to control the speed of the motor. With their current generation of humidifiers, Venta controls the motor through a fully electronic control board with two buttons to turn the device on/off and to change level by one.

Opening the device shows the main PCB, which is connected to a control panel (with the switches and LEDs visible at the upper side of the humidifier) through a 10-pin IDC flat band cable. The power supply is a 24V external power supply that is plugged into the control panel. The schematics of the control panel is as follows:

The control panel has the following features:

  • Four LEDs indicating Power On, the level (1-3) and a red error LED. All of them are controlled by the main PCB by pulling the corresponding pin of the connector to low
    • To detect current power status, level and error status, one can simply read out the pins of the connector.
    • To light up a LED, the corresponding PIN needs to be pulled to GND.
  • The power and level buttons simply connect the corresponding pin of the connector to GND.
  • The sensor to detect an opened device is implemented as another button, which again connects to GND when the device is opened.

Looking at this schematics, it is apparent how a WiFi control can be easily added to the LW45 humidifier:

  • Insert a WiFi-enabled PCB between the main PCB and the control panel
  • That PCB would read out pins 2, 4, 6, 8 and 10 of the cable/connector to detect the power status, level and error status.
  • To turn the device on/off or switch levels, the pins 7 or 9 are connected to GND by the microcontroller.
  • To detect an opened device, pin 5 is read (GND means device open)
  • To light up the error LED, pin 10 need to be pulled to GND.

All these steps can be easily done by any microcontroller used in smart home applications. The only problem is the power: The VCC is 24V and the levels of the LED pins are potentiall 24V!

hardware/venta_connected.1539358438.txt.gz · Zuletzt geändert: 2018/10/12 17:33 von reinhold

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