SK ENGINEERS

  CLASSIFICATION OF CONTROL SYSTEM A.        Open loop control system (NO feedback control system) B.      Closed loop control system (with feedback control system) 1.       OPEN LOOP CONTROL SYSTEM ·         The system which doesn’t have any feedback loops connected to it is called “open loop control system”. ·         These type of systems doesn’t depend upon its output i.e. in open loop feedback system, output is not used as the control variable for the system. ·         Open loop systems are one way signal flow systems. ·         As these systems doesn’t contain a feedback loops, these are also known as Non feedback systems. ·         As there is no feedback loops, no data is transferred back to the open loop systems. · ...

  TIMERS DEFINITION : A timer is a special counter ladder function that allows the PLCs to perform timing operations based on a precise internal clock. TYPES OF TIMERS : 1.       Delay ON timers or ON delay timers 2.       Delay OFF timers or OFF delay timers 3.       Pulse timers 4.       Cascaded timers 5.       ON-OFF cycle timers 6.       One shot timers 1)      DELAY ‘ON’ TIMERS : ·         The term delay is used to indicate that this timer burns on, after waiting for a fixed time delay period. ·         When there is an input, the timer is energized and start timing, after some pre-set value, the timer contacts are closed to outputs. ·         TON is used to denote ON- delay. 2 ...