Relay Delay

Question

I want to make a delay, so that when the circuit turns on, it takes a while for it to come on.

D_Hersey · Accepted Answer

Heavens Tbilisi! 'A while!' I will presume a coupla seconds like you are shorting out the current limiter on a bypass cap. 'Turns on' is also problematic if you don't specify after being off for at least so-and-so period. I will further presume your excitation is DC. You hook up a RC string across the supply. The tap goes to one of the inputs of a voltage (hate that word!) comparator. The other input is a reference, like a backwards Zener (or coupla LEDs, even) with a ballast R, maybe, say 2/3s Vcc. Timing cap charges, changing potential at the tap, comparator triggers Q which fires relay. Comparator has provisioning to avoid the jits, such as Schmidt action. Alternatively, Norton comparator with input resistors. If you need more time, one option is a capacitance multiplier circuit.

Relay Delay

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