time delay relays (TDRs)
No matter what the application is, when a definite-purpose
solution is required, time delay relays (TDRs) can provide
simple, reliable, and economical control. Adjusting the delay
time is often as simple as turning a knob. Providing time-
delayed switching to start a motor, control a load, or affect a
process,
time delay relays (TDRs)
TDRs are typically used in industrial applications
Additionally, they play an important role for targeted logic
needs, such as in a small panel or in sub-panels. They have
a variety of features and operating characteristics, such as
compactness, economy, simplicity, and ease-of-use
time delay relays (TDRs)
On-delay timers
With an on-delay timer, timing begins when voltage is
applied. When the time has expired, the contacts close — and
remain closed until voltage is removed from the coil. If
voltage is removed before time-out, the time delay resets
Time-delay relay contacts
Time-delay relay contacts must be specified not only as
either normally-open or normally-closed, but whether the
delay operates in the direction of closing or in the direction
of opening.
Normally-open, timed-closed
Normally-open, timed-closed. Abbreviated “NOTC”, these
relays open immediately upon coil de-energization and close
only if the coil is continuously energized for the time duration
period. Also called normally-open, on-delay relays.
Normally-closed, timed-open
Normally-closed, timed-open. Abbreviated “NCTO”, these
relays close immediately upon coil de-energization and open
only if the coil is continuously energized for the time
duration period. Also called normally-closed, on-delay relays.
Off-delay timers
When using an off-delay timer, nothing happens when voltage
is applied. Closing the control input causes the contacts to
transfer Opening the control input causes timing to begin,
and the contacts remain closed. On time-out, the contacts
transfer. Closing the control input prior to time-out causes
timing to reset.
Normally-open, timed-open
Normally-open, timed-open. Abbreviated “NOTO”, these
relays close immediately upon coil energization and open
after the coil has been de-energized for the time duration
period. Also called normally-open, off delay relays.
Normally-closed, timed-closed
Normally-closed, timed-closed. Abbreviated “NCTC”, these
relays open immediately upon coil energization and close after
the coil has been de-energized for the time duration period.
Also called normally-closed, off delay relays.
Off-delay timers
Removing voltage prior to time-out resets the timing and
opens the contacts. In addition, true off-delay timers provide
this functionality (keeping contacts closed) after input
voltage is lost.
practice
question
Time-delay relays are important circuit elements in many
applications. Determine what each of the lamps will do in the
following circuit when pushbutton A is pressed for 10 seconds
and then released:
question