Time Delay Relay
A time delay relay matches the general outline of a normal relay , but is not instantaneous. A Time Delay relay can hold a power supply anywhere from 2 seconds to about 3 minutes once power is removed. These Time- Delay relay contacts must either be Normally Open or Normally Closed, as well as a specification on how the delay operates. This may sound complicated, but in reality, it is basically asking if the delay is an “on-delay” or an “off-delay. An “on-delay” timer starts immediately when the voltage is applied. Once the selected delay time is complete, the contacts will close. These contacts will then stay closed until the beginning voltage is not going to the coil.
On the opposite side, an “off-delay” timer does not start when voltage is applied. One needs to open the control input before the timing actually begins and the contacts will remain closed during this time. Once this time is complete, the contacts will open and the relay will shut off.