Siemens LOGO!8: My DIY Experience with Smart Lighting Control System

Introduction

Hello everyone, I am Lao Wang. I have been working in the automation industry for over ten years, evolving from a novice to someone who can independently design small automation projects. Today, I would like to share my experience in implementing a smart lighting control system using Siemens LOGO!8.

I remember when I first encountered PLCs, I was overwhelmed by various technical terms and complex wiring diagrams. If someone had explained it to me in a simple and clear way back then, I could have avoided many detours. Therefore, in this article, I will try to share my practical experience in the most straightforward language, especially for friends who are interested in smart homes but feel that the threshold is too high.

Hardware Preparation

First, we need to prepare the following devices:

• Siemens LOGO!8 basic module (I am using the 0BA8 model)
• Expansion module DM8 (if controlling multiple lights)
• 24V DC power supply
• Relay module (for controlling high-power lights)
• Light sensor (to detect ambient brightness)
• Human infrared sensor (to detect presence)
• Button switch (for manual control)
• Connecting cables

Tip: When purchasing hardware, it is recommended to choose legitimate channels to avoid counterfeit products. I once bought a “super low-priced” LOGO! module, and it burned out in less than two months, forcing me to spend more money to buy a genuine product.

System Design Concept

My smart lighting control system mainly implements the following functions:

1. Automatically turn on/off lights based on ambient brightness
2. Automatically turn on lights when someone is detected, and turn off after a delay when no one is present
3. Manual control has a higher priority than automatic control
4. Support setting different lighting modes for various scenes

When designing this system, the core principle I followed was: simplicity and practicality, easy maintenance. As a DIY project, we do not need overly complex functions, but rather ensure that the system is stable and reliable, making troubleshooting easier when issues arise.

Wiring and Installation

The wiring for LOGO!8 is relatively simple, but there are a few points that need special attention:

1. Ensure that the power supply wiring is not reversed
2. Input devices (sensors, buttons) should be connected to the I terminals
3. Output devices (relays, indicator lights) should be connected to the Q terminals
4. Analog input (such as light sensor) should be connected to the AI terminals

I recommend drawing a wiring diagram before connecting to ensure that each device’s connection points are clear. The first time I wired, I went by feel, resulting in a tangled mess that made debugging particularly painful.

Programming

Programming LOGO!8 can be done using the LOGO! Soft Comfort software, which provides a user-friendly graphical programming interface. The main logic is as follows:

1. Read the light sensor value and set the threshold trigger conditions
2. Set the trigger logic and delay parameters for the human detection
3. Set the control priority for the manual button
4. Write the logic for different scene lighting modes

Some important functional modules I used in programming:

• Analog comparator: used to compare the light sensor value with the set threshold
• Delay relay: sets the delay time for turning off the lights after no one is detected
• RS trigger: implements priority locking for manual control
• Time relay: for timed on/off light functionality

Tip: Be sure to add clear comments for each functional block during programming; it will save a lot of trouble during future maintenance. I once didn’t touch a program for six months, and when I looked at it again, I found it had no comments, making it hard for me to understand the logic I had originally implemented.

Debugging and Optimization

After the system is built, debugging is a critical step. My debugging process is as follows:

1. First, test whether each sensor is functioning properly
2. Verify each control logic one by one to ensure it meets expectations
3. Adjust sensor sensitivity and delay parameters
4. Simulate various usage scenarios for testing

Typical issues encountered during debugging:

• Improper threshold setting for the light sensor, causing frequent on/off switching
• Improper angle for the human sensor, resulting in detection blind spots
• Delay parameters set too short, causing the light to turn off just after someone leaves

Solutions:

I recommend setting a “hysteresis” for the light sensor, meaning the thresholds for turning on and off the lights are different to avoid frequent switching near the critical value. It is best to choose a wide-angle model for the human sensor and install it in a position that can cover the entire area. Delay parameters should be set longer, such as 3-5 minutes, to improve the user experience.

Practical Application Cases

I first applied this system in my living room. The effect was excellent, especially at night when I come home, the lights automatically turn on, eliminating the hassle of searching for the switch in the dark.

Later, I helped set up a system for a small conference room in my company. The lights automatically turn off when the conference room is unoccupied, greatly saving on electricity costs. According to rough estimates, this alone can save several hundred kilowatt-hours of electricity each year.

What impressed me the most was installing the system for an elderly person with limited mobility. The automatic sensing lighting system significantly reduced the risk of walking in the dark. The elderly person praised this system, saying it was better than any electrical appliance they had used before.

Common Issues and Solutions

1. System occasionally malfunctions

   • Check if the power supply is stable; install a UPS if necessary
   • Check if the sensor connections are secure

2. Lighting flickers inconsistently

   • Check if the relay is of good quality
   • Confirm if the power supply capacity meets the requirements

3. Settings cannot be saved

   • Check if the LOGO! module has a battery or if the battery needs to be replaced
   • Write important parameters to the permanent storage area

Conclusion

After creating so many smart lighting control systems, my biggest realization is: technology is not the goal; improving the quality of life is. No matter how complex the system is, it ultimately serves human needs.

During the DIY process, do not be discouraged by problems; research more and consult experts. I often immerse myself in Siemens’ technical forums, where most of the issues I encounter have already been solved by others.

Finally, I welcome everyone to share their DIY experiences or suggest improvements to my solution. Technology progresses through communication; let’s learn and grow together!