Timer Relay Functions and Timing Diagrams
Compare on-delay, off-delay and interval relay behavior using trigger and output timing diagrams, then check reset behavior, trigger type and timer power requirements.
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Compare idealized timing functions
A timing function relates a defined trigger to a defined output state. Power-on, a separate signal input and signal removal are different trigger events. Read the selected product mode and contact diagram together; a dial setting alone does not identify the function.
| Function | Trigger and output concept | What the manual must define |
|---|---|---|
| On-delay | After the trigger becomes active, output waits for the set time. | Whether the trigger is supply power or a signal, and how early removal resets the timer. |
| Off-delay | Output is active during the trigger and remains active for the set time after removal. | Required sustained timer power or the specifically supported power-off-delay design. |
| Interval | Trigger starts an immediate output pulse of the set duration. | Retriggering, early trigger removal and reset behavior. |
| Repeat cycle / flasher | Output alternates on and off according to the selected timing sequence. | First state and whether on/off times are independently adjustable. |
Read the timing diagram
In the idealized diagrams, high means active, low means inactive, and t marks the set interval. On-delay begins timing at the rising trigger edge. Off-delay begins timing at the falling trigger edge. Interval begins its output pulse at the rising trigger edge. The drawings assume a suitable sustained timer supply and omit reset/retrigger details.
A relay output may contain instantaneous and timed contacts on the same product. Check the actual contact designation. Do not infer a timing function or a normally closed contact action from a generic relay terminal number.
Record the chosen mode
- Write the exact model, supply voltage and mode selector position.
- Identify the trigger terminal or supply event and its normal state.
- Record time range, dial setting, output contact and reset time.
- Check power-loss response and the effect of a repeated trigger.
Use terminal markings for contact identification and control diagrams for ordinary command logic. A timer alone does not establish a machine safety function.