Timers and Smart Relays. Flashcards Preview

Electrical Lab MCSC Period 2 SAIT-Alberta > Timers and Smart Relays. > Flashcards

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What are the three basic types of timing devices?

Spring-wound interval timers.
Mechanical and electronic time switches.
Timing relays.


Is a spring wound interval timer used when precision of timing is required?

No, it is not very accurate and inexpensive.


What are mechanical and electrical time switches generally used for?

Security lighting control.
Landscape irrigation.
Parking receptacle circuits.


How would one adjust a panel mount timing relay?

Timing is adjusted by connecting the appropriate resistors to terminals on the relay.


What are the two basic timing functions a relay can provide? There are three additional functions used by a multi-function relay, what are these?

Time delay on energization (TDOE),
Time delay on de-energization (TDOD).

One - Shot,
Repeat cycle.


If an interval relay was started and the relay lost power, would the timing interval be interrupted?

Yes, the timed contacts would immediately open. Generally speaking, a timing relay requires power to keep the contacts energized.


Which function, always utilizes an initiating circuit with dry contacts?

One - shot.


What must be used in any basic TDOD circuit?

A mushroom stop button, to maintain safety.


How must a smart relay input be connected?

The input simply registers voltage for the internal programmable contact to close. This may be interrupted by a pushbutton or switch to serve as the input.


How does a smart relay output work?

A smart relay output is simply a set of normally open contacts which close, when the path of the ladder logic program allows it.


Are smart relays generally more advanced/useful than timing relays?

Yes, they are fully programmable and have an abundance of timing functions.