Timers and Smart Relays 030204b

Question 1

What are three basic types of timing devices?

Timers and Smart Relays ILM

Answer 1

Spring-wound interval timers.

Mechanical and electronic time switches.

Timing relays.

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Question 2

What are spring-wound interval timers commonly used for?

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Answer 2

Lights.
Fans.
Bathtub spa motors.
Sauna heaters.

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Question 3

What is the disadvantage of spring-wound interval timers?

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Answer 3

Not very accurate or precise.

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Question 4

What are mechanical and electronic time switches commonly used for?

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Answer 4

Security lighting.
Landscape irrigation.
Parking receptacle circuits.

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Question 5

What type of timer use a small electrically driven clock motors that control adjustable trip mechanisms or cams to change the state of the contacts?

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Answer 5

Mechanical Time switches.

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Question 6

What are three methods of controlling the timing of a timing relay?

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Answer 6

Pneumatically (by air).
Fluid-filled dashpot.
Electronically.

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Question 7

What are the five basic timing functions provided by timing relays?

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Answer 7

TDOE (Time Delay on Energization) also known as on-delay or delay-on-operation.
TDOD (Time Delay on De-energization) also known as off-delay.
Interval timing
One-shot timing
Repeat cycle timing.

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Question 8

How do time delay on energization (TDOE) contacts work?

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Answer 8

Contacts change state after a specified amount of time on energization.
Will immediately revert back to normal state on de-energization.

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Question 9

How do time delay on de-energization (TDOD) contacts work?

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Answer 9

Change state immediately on energization.
Revert back to normal state after a specified amount of time after de-energization.

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Question 10

How do interval timing contacts work?

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Answer 10

Change state instantly on energization.
Revert to normal state after a specified amount of time regardless if the coil remains energized.

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Question 11

How do one-shot timing contacts work?

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Answer 11

Require a start signal.
Once the start signal is activated the contacts change state for a specified amount of time then revert back to normal state.
Remain in normal state until they receive the start signal again.

Example: pop machine or oil-spray pump on a lathe.

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Question 12

How do repeat cycle timing contacts work?

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Answer 12

Contacts cycle from normal to changed state until de-energization.
Can be initited by energization or by a start signal.

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Question 13

What is a smart relay?

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Answer 13

Simple relays and/or timers that are programmable.
Have memory to store programs.

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Question 14

How can smart relays be programmed?

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Answer 14

Through the relay’s keypad or a computer.

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Question 15

What programming languages are smart relays typically programmed with?

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Answer 15

Ladder logic.
Function block.

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Question 16

What are smart relays often compared to?

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Answer 16

Small programmable logic controllers (PLCs)

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