- Jan 1, 1970
I need to power a relay from 120 vac such that its action is delayed for a
few seconds after power-on. I realize that this means getting DC voltage (via
diode) and an R-C combination.
Ideally, a relay with DC-rated coil would be most appropriate, but I've got a
nice new relay with properly-rated contacts sitting on the shelf with a coil
rated at 24 vac, 330 ohms, 71 mA.
How complex would it be to run this relay with mains voltage? Is it as simple
as a diode followed by a resistor? Would this resistor be 120/0.071/2 = ~500
ohms and 2.5 watts?
And a fundamental question: can a relay with an AC coil function properly &
reliably on DC?
Since I need to delay the relay's turn-on, I'll be adding a capacitor,
anyway, whether I use this relay or a true DC-rated type. What should the
value of the capacitor be to give me a 1 or 2 second delay with the 500 ohm
resistor (or, if I've miscalculated that value, with the proper value
Any observations, suggestions, corrections (I'm getting used to these!!) are