Example Program for ALPHA Series

5. Humidity Control in Greenhouse
 

 

 

In this example a humidifier is operated to increase the humidity in a greenhouse when it falls below the specified percentage. A humidity sensor and the ALPHA series' analog input (0 to 10 V), Offset Gain, and Schmitt Trigger are used to control the humidifier.

Contents of Control:

  1. When the automatic mode button (S1) is pressed, the automatic operation of the humidifier starts. The humidifier is operated when the indoor humidity falls below 50% until it reaches at least 70%. This automatic operation continues until the stop automatic mode button (S2) is pressed.
  2. When the manual mode ON/OFF button (S3) is pressed during the automatic operation, manual mode is entered. The humidifier operates or stops according to the status of the button (S3).
  3. When the manual mode ON/OFF button (S3) is set to ON, the humidifier operates, and when it is set to OFF, the humidifier stops.

How to convert output of humidity sensor (1 to 5 V) into humidity percentage (%)

In this example 0 to 100 % have to be converted into 1 to 5 V. Set the following linear function calculation in the function block Offset Gain to convert the input voltage into an analog value.

Installing and Wiring:

  1. Refer to the ALPHA/ALPHA2 Hardware Manuals for correct installation and wiring procedures.

Program:

  1. Refer to the ALPHA/ALPHA2 Programming Manuals for explanations concerning function blocks and program input. Refer to the ALPHA Software Manual when using the AL-PCS/WIN-E programming software.