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Controlling VAV Regulators with CO2 Sensors using LOGO8

Hi Martin,

Here's how you can control VAV regulators linearly with a CO2 sensor using LOGO8. Since you're familiar with TIA Portal, the LOGO!Soft Comfort environment will feel similar, but simplified.

Approach: Analog Scaling

LOGO8 can scale the analog input (CO2 sensor reading) to an analog output (VAV regulator control signal). This is done using the "Analog Scale" block.

Steps & Example Code (LOGO!Soft Comfort):

1. Input: Connect your CO2 sensor's analog output (4-20mA or 0-10V) to an Analog Input (AI) on the LOGO8.
2. Output: Connect the VAV regulator to an Analog Output (AO) on the LOGO8.
3. Network Configuration:
   • Drag an "Analog Scale" block onto your network.
   • Input: Assign the AI where your CO2 sensor is connected.
   • Input_Min: Set to 600 (representing 600 ppm CO2).
   • Input_Max: Set to 1100 (representing 1100 ppm CO2).
   • Output_Min: Set to 0 (representing 0V output).
   • Output_Max: Set to 10 (representing 10V output).
   • Connect the output of the "Analog Scale" block to the AO connected to your VAV regulator.

Example: The scaled value will be linearly mapped between 0V and 10V based on the CO2 level.

Resources:

• LOGO! Soft Comfort Help: Search for "Analog Scale" in the LOGO! Soft Comfort help files for detailed information.
• Siemens Support Article: https://support.industry.siemens.com/cs/ww/en/view/109789196 (Example of Analog Scaling)
• LOGO! 8 Training: https://new.siemens.com/global/en/products/automation/logo/training.html

This approach offers a simple and effective way to achieve linear control of your VAV regulators based on CO2 sensor readings. Let me know if you have any further questions.

Best regards,

Siemens Self Support