Study the ladder logic program in Figure and answer the questions that follow: a
ID: 2081082 • Letter: S
Question
Study the ladder logic program in Figure and answer the questions that follow: a. Under what condition will the latch rung 1 be TRUE? b. Under what conditions will the unlatch rung 2 be TRUE? c. Under what condition will rung 3 be TRUE? d. When PL1 is on, the relay is in what state (LATCHED or UNLATCHED)? e. When PL2 is on, the relay is in what state (LATCHED or UNLATCHED)? f. If ac power is removed and then restored to the circuit, what pilot light will automatically come on when the power is restored?Explanation / Answer
a) Rung 1 will be true when input 1 (I1) and Input 2 are true or on.
b) Rung 2 will not be true as input 3 is a normally closed switch and hence will remain de energised even when rung looses power.
c)Rung 3 will be true whenever PL1 is not on i.e. Rung 1 is not true.
d) Unlatched. When PL1 is on, I3 should be off, i.e. relay should be unlatched
e) Latched. When PL2 is off, i3 should be on, i.e. relay should be latched.
f)PL2 will turn on as when power comes on as I3 is normally closed and unlatches PL1, hence rung 3 becomes true and PL2 turns on.