# PLC Ladder Logic: Smart Window Blind System

## 7 posts in this topic

I have a PLC ladder logic problem that I am stuck with and would like to know if there is a solution for it.

PLC Ladder Logic Problem on PLC Fiddle: Automatic Window Blind

There is a window blind that is controlled by using an opening and closing motor. There are 2 IR sensors that act as limit sensors to identify the boundaries of the opening and closing of the blind. The blind can either fully open or fully close. The blind is fully opened during day time and is fully closed during night time. We assume that the day time is for 12 hours and night time is for the other 12 hours. The PLC ladder logic must include at least a SENSOR, an ACTUATOR, a TIMER, and a COUNTER. You may use PLC Fiddle to draw the ladder logic: https://www.plcfiddle.com/

The process is as follows:

1. Assuming that the blind is now fully closed (during night), the night time 12-hour count down starts. The counter is done using a timer that counts 1 second, and after every second, the counter goes down starting from initial value of 12 (1 second represents 1 hour count down for simplicity).

2. When night time counter reaches 0, the counter resets back to 12 and stops, then the blind opening motor activates and keeps running until the blind edge reaches the opening limit sensor.

3. The opening motor then stops, and the day time 12-hour count down starts. The day time counter operates the same as the night time counter.

4. When day time counter reaches 0, the counter resets back to 12 and stops, then the blind closing motor activates and keeps running until the blind edge reaches the closing limit sensor.

5. The closing motor then stops, and the night time 12-hour count down restarts again. The whole process is repeated again.

Please find attached below the rough sketch for the idea. Feel free to either sketch the ladder logic or use PLC Fiddle (link above). Thank you.

Edited by hisham

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Is this an assignment for school? Show what you have so far and someone will likely help out.

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18 hours ago, panic mode said:

I've used it several times when I didn't have an actual PLC available.

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unlike https://app.plcsimulator.online/ plc fiddle does not work on mobile phone but otherwise it looks very similar in capabilities.

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I'll have to check that one out.

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they are quite similar, both have similar instruction set, both require declaring variables to hold some value (cannot enter literals). i prefer look of thin lines of plc fiddle and more intuitive insertion of instructions but plcsim online has better handle on scrolling, instructions are in one group and always visible.