Auxiliaries relays can be used in a number of ways with different accessories to obtain a variety of types of operation. By adding some extra accessories, a relay can do more in addition to its normal functionality.
Plug-in units with e.g., diodes, resistors and capacitors are readily available by manufacturer. This plug in unit can be insert in front or rear side as per manufacturer.
Drop-out time-lag by auxiliary relay with a diode:
For below image- Drop-out delay can be achieved by connecting a parallel diode across the relay coil as shown. The polarities of the dc voltage and the diode must be cared. When S makes the relay picks up instantaneously. When S breaks the relay drops out.
Pick-up time-lag by auxiliary relay using a thermistor
[alvaa]When S makes, the current heats the thermistor t and its resistance drops as its temperature increases. When the current through R reaches the pick-up value, the relay picks up and the thermistor is shortcircuited by a make contact on the relay.
Pick-up and drop-out time-lag by auxiliary relay using a capacitor
When S makes, the pick-up time is determined by the values r, R and C. The relay picks up when C is sufficiently charged and the time lag upon drop-out is caused by C discharging through R after S breaks