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DC time delay? Answered

Here's the situation-I close a switch completing a circuit,providing DC power to a load(6 volt,0.1 A).But I do not need the load to start functioning as soon as the switch is closed i.e,only after a delay of say..30 seconds.I googled for "Time delay circuits" but the ones I got were either dealing with AC or the transistor -capacitor(Time Constant) based circuits that makes a load function for a preset time after the circuit switch is opened.I think I could achieve this "pre-delay"  with elements such as transistors,resistors,capacitors etc. but I can't figure out how.Please suggest possible circuits that can be used to achieve my purpose.



Best Answer 5 years ago

Here is a very simple After Relay.

Once turned ON the capacitor C begins charging through resistor R

Eventually the capacitor voltage rises high enough to trip the Diac
and turns  ON  the SCR  which  Closes the Relay .

This will stay closed until power is turned OFF !


After-timer scr.GIF

Use a 555 timer to operate either a relay or a transistor as a switch.

main switch operated the 555 and the end of time operates the relay to turn on the main circuit.

I don't have much experience with the 555 but I think u r talking about its astable mode.Could you add a schematic to give me a good idea?Appreciate it.