Summative Test: Relay, Counter & Timer

When a relay’s coil is energized, the magnetic field pulls the armature to close the contact. What type of logic operation does this action resemble?

• OR

• AND

• NOT

• NAND

A solid-state relay is preferred over an electromechanical relay in automation systems because it:

• Costs less and is easier to replace

• Produces more noise when switching

• Has moving parts that wear out faster

• Has faster response and longer lifespan

If a circuit is designed to activate a motor only when both sensors A and B are active, which logic gate describes this behavior?

• OR

• AND

• XOR

• NOR

Which situation best demonstrates the application of a relay’s Normally Open (NO) contact?

• The light is on until the switch is pressed.

• The light remains off until the coil is energized.

• The current always flows through the contact.

• The coil is permanently disconnected.

A delay-on timer (TON) is used to start a motor fan 3 seconds after power is applied. What is the purpose of this delay?

• To test the circuit’s current load

• To prevent surge current and mechanical stress

• To increase the motor speed gradually

• To shorten the operation time

If the accumulated value of a timer equals its preset value, what happens to the done bit (DN)?

• It remains 0

• It resets automatically

• It changes state to 1

• It disables the timer

A relay can function like a logic gate. If the relay coil is energized only when both Switch A and Switch B are ON, which type of logic gate does this operation represent based on the truth table below?

• OR Gate

• AND Gate

• NOT Gate

• NOR Gate

What is the primary difference between a delay-on and a delay-off timer?

• Delay-on activates output immediately

• Delay-off keeps output energized after input is removed

• Delay-on has no preset value

• Delay-off only works with relays

If a logic gate outputs “0” only when both inputs are 1, what kind of gate is it?

• NAND

• AND

• XOR

• OR

You observe that a relay coil is energized, but the output device does not operate. Which is the most logical first step to troubleshoot?

• Replace the relay

• Check the coil voltage

• Verify the contact rating and wiring

• Change the load device