Solid State Timers and Time Delay Relays
Time delay relays and solid state timers are devices used to provide a time delay. The most common types of timers are: (i) ON-delay and (ii) OFF-delay timers.
The application of a signal initiates the time delay. At the end of the delay, the load is energized or de-energized, depending on the normal state of the contacts (open or closed, respectively).
The removal of the input power causes the timer contacts to open or close, depending on their normal state.
Other types of solid state timers are:
Single-shot timers. The application of power causes the contacts to change position and remain so for the specified time delay. It is measured one output pulse for each rising-edge transition in the input.
Interval timers. The application of power initiates time delay, during which the output is energized.
Recycle timer. As long as power is applied the load is energized and de-energized at regular intervals.
Time delay relays and solid state timers are used in industrial control circuits, such as engine auto-start control, motor soft-start delay control and flashing light control.