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Programmable Logic Controller (PLC) Questions and Answers – 1

Suppose we have a PLC connected to three pushbutton switches as shown in this illustration:

PLC Questions - 1

In the above diagram :

  • X1 to X4 : Digital Inputs
  • Y1 to Y4 : Digital Outputs

Determine the switch actuation statuses (i.e. pressed versus released) given the “live” display of the ladder logic program shown here:

PLC Switch Logic

Also, determine the status of the lamp connected to the PLC’s Y1 output.

Answer :

Switch statuses:

  • Switch A = pressed
  • Switch B = released
  • Switch C = released

The lamp will be de-energized.

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Credits :  Tony R. Kuphaldt – under CC BY 1.0

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jairo francisco October 23, 2017 at 1:27 pm

A lampada só acenderar se A e C for prenssionados juntos

Translated : The lamp only glow if A and C together is present.

ali alghasham June 12, 2018 at 8:39 am

thank you

Hitesh December 31, 2018 at 12:50 pm

The lamp only glow without any action on pushbutton means exiting field wiring and logic instruction condition is true when power on


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