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PLC traffic light


This ladder logic simulates a 4 stages traffic light. By closing the switch connected to the input 2 the yellow lamps flash with a frequency depending on the timers TIM09 and TIM10. When the button connected to the input 0 is pressed the traffic light starts working. The green lamps are connected to the inputs 100,103,106,109; the yellow lamps are connected to the outputs 101,104,107,110; the red lamps are connected to the outputs 102,105,108,111. The green signal duration can be set by the timers TIM01,TIM03,TIM05,TIM07. The yellow lamps duration depends on the timers TIM02,TIM04,TIM06,TIM08. Due to the timers TIM11,TIM12,TIM13,TIM14 each green light turns on two seconds after the red lamp of the previous stage. By pressing the button connected to the input 1 the traffic light stops working.

Ladder diagram (pdf)