is Interview question that every PLC programmer came across in his
carrier.The Question is very tricky and shows the fundamentals (basic Ladder
Laws) and depth of candidates knowledge.
we are going to discuss PLC program for Push to ON device and Push to Off
Device.But the trick is that we have to use only Normally open(NO)
,Normally Close (NC) contacts ,and Coil as output only(No timer,Counter, OSR ).
In short there will be a single Push Button Input (X0) , and one Output (Y0).
When user press Push button for 1st time output will be ON ,when user Presses
Push Button for 2nd time output will be OFF. This is also called as “Push
to On Push to Off ” logic.Analogy can be provided with “TV” on
and off Push Button.
only NO,NC,Coil only
- Using OSR
(Rising Edge ,Falling Edge) Instruction
Note:Do not Replace M0 with Y0
Below Program is using Counter instruction
Question asked on this are related to Scan time and rung interchange etc.
Check Video Demonstration of Above Program