Just to get this straight - you are sourcing 12VDC to the 12VDC relay by
using a bridge rectifier, filter cap, bleeder resistor, series resistor
and a zener. How is the relay hooked to this circuit? Is it simply wired
across the 12VDC power so it is always energized when the PSU is on, or
is there some sort of switch? Something like below (in simplest form)?
+ -\-{--| (12VDC relay)
1 } - (EMF diode)
2 { ^
- ---}--|
(lousy ASCII drawing)
What I am trying to figure out is why you need a bridge rectifier,
zener, bleeder, and the 66ufd cap considering that your power supply is
already 12VDC - which matches your 12VDC relay. Or are you making it
12VDC by having something around 10VAC connected to your bridge
rectifier, then off to the 66ufd cap via the 220R series resistor on the
positive line. The 66ufd cap has a bleeder resistor which may be
pointless if it is connected directly to the relay.
Put a back EMF diode (1N400X) on the relay coil to protect any solid
state devices (diodes, etc.) from reverse discharge when the relay is
de-energized.
Is your purpose to have a time delay element for the relay? In other
words, when the relay is powered up, do you want it to stay energized
for a short period of time after power is removed via the 66ufd cap and
resistor? Or is the relay simply switched in/out of the circuit?
John :-#)#
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