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Controlling a Fan with Pressure Measurement using LOGO! 8

Hello! Welcome to the world of LOGO! I'm Siemens Self Support, integrated with SiePortal, and happy to help you get started. Here's an example to control your fan based on pressure, with display control and setpoint functionality.

Application Overview

This example uses a 0-10V pressure signal to control a fan's speed, maintaining a constant pressure of 55 Pa. The LOGO! will regulate an analog output (0-10V) to a fan controller. A display will show current pressure and allow setpoint adjustments.

LOGO! Program Structure

1. Analog Input: Connect your 0-10V pressure sensor to an analog input (e.g., AI1).
2. Analog Output: Connect the 0-10V analog output (e.g., AQ1) to your fan controller.
3. Setpoint Input: Use a display (e.g., VD1) to set the desired pressure (55 Pa). Map the display value to a 0-10V equivalent for the setpoint.
4. Comparison & Control:
   • Use a comparison block (e.g., <,>to compare the analog input value (pressure) with the setpoint value.
   • Use a PID block (if LOGO! version supports it, or implement a simple proportional control) to adjust the analog output based on the difference between the measured pressure and the setpoint.
5. Display: Display the current pressure reading on the VD1.

Example Configuration (Simplified)

• AI1 (Analog Input): Input from pressure sensor (0-10V representing 0-Max Pa). Scaling needed in LOGO! to convert voltage to Pa.
• AQ1 (Analog Output): Output to fan controller (0-10V).
• VD1 (Display): Displays current pressure, allows setpoint input (0-10V representing 0-Max Pa).
• Comparison Block: AI1 < VD1 (Setpoint)
• Control Logic: If AI1 < VD1, increase AQ1. If AI1 > VD1, decrease AQ1. Adjust the 'gain' of this control to avoid oscillations.

Resources

• SiePortal: Siemens LOGO! Support
• LOGO! 8 Manual: Refer to your LOGO! 8 manual for detailed instructions on configuring analog inputs/outputs, displays, and comparison blocks.
• Example Projects: Search SiePortal for example projects related to analog control.

This is a simplified example. Proper scaling of analog inputs/outputs and tuning of the control loop are crucial for optimal performance. Experiment with the control logic and gain to achieve stable pressure control. Keep learning and exploring, and you'll become a LOGO! expert in no time!