RLD Practice Question

Relay Logic Design

Practice Questions Set

Q1.  Use a single switch to control an output, i.e. when pressed – O/P is high and when released O/P goes low?

Q2.  Use two switches and the O/P should activate (go high) only when both the switches are pressed?

Q3.  If two switches are used to control a motor and the logic says that the O/P should turn ON when any one of the two switch is pressed?

Q4.  Draw the Control and Power ckt to control a motor when only a single switch is provided?

Q5.  Implement a NOT gate using a single switch? Draw the truth table as well?

Q6.  Use two switches; one should turn ON the O/P and the second to turn it OFF. Draw the control ckt.

Q7.  Given only one NO switch it is required that the motor connected to it should turn OFF when the switch is pressed? Explain the overall process as well.

3-Switch Analogy

Q8.  Given three switches I₁, I₂, I₃ to control the O/P, it is mandatory that all the three switches are pressed to activate the O/P.

Q9.  For the same 3 switches we need the control to be a bit modified and now the O/P should activate when any one of them is pressed.

Q10.                  The O/P should turn ON only if one of the three switches is pressed at a time.

Q11.                  The three switches I₁, I₂, I₃ should be arranged such that the O/P should turn ON only when any two switches are pressed together.

Multiple O/P Analogy

Q1.  Implement Half Adder using the RLD; provide the truth table and the Boolean equation.

Q2.  Given two switches use one to run a motor in forward direction when pressed and another for rotating the motor in reverse. The motor used is a 3-phase motor.

Q3.  If three switches are provided namely  I₁, I₂, I₃, and three motors M₁, M₂, M₃ are to be controlled using them according to the below instruction, draw the control logic for them.

a)       I₁ is pressed ----- M₁ turns ON,  when I₂ is pressed ---- M₂ turns ON and when I₃ is pressed ----M₃ Turns ON

b)       I₁ is pressed ----- M₁ turns ON,  when I₁ I₂ is pressed ---- M₂ turns ON and when I₁ I₂ I₃ is pressed ----M₃ Turns ON

c)       I₁ is pressed ----- M₁ turns ON,  when I₁ I₂ is pressed ---- M₁M₂ turns ON and when I₁ I₂ I₃ is pressed ---- M₁M₂ M₃ Turns ON

d)       I₁ is pressed ----- M₁ turns ON,  when I₂ is pressed ---- M₁M₂ turns ON and when I₃ is pressed ----M₁M₂ M₃ Turns ON

e)       Use relay O/P interfacing to simplify the logic designed for the above problem (d).

Draw the logical control ckt using the truth table for all the problems.

Reverse /Forward Action of Motors

Q1.  Use two switches one to reverse a 3-phase motor and another one to move the motor in forward direction it should be kept in mind that the motor should not move(be in off condition) if both the switches are pressed together. Draw the Control and Power Ckt for it.

Q2.  Use single physical switch as resources are limited we cannot use an interfacing from the O/P relay and hence have to manage from the switches provided. Design a Control and Power logic such that the motor runs in forward and reverse direction when the switch is pressed and when released. Draw it using two switches in control logic.

Q3.  For the same condition of Q3 draw a control and power ckt using a single switch in logic instead of previously given two.

Q4.  Repeat all the above three questions(Q1, Q2, Q3) using an extra switch to turn the motor off, as the motor will keep running in forward or reverse direction until supply is disconnected.