"David Nebenzahl" wrote in message
s.com...
On 3/29/2009 6:43 AM Baron spake thus:

David Nebenzahl wrote:
Ok but excuse the ascii art.

live ----diode---relay---resistor---capacitor---neutral

You're excused. That illustrates the circuit perfectly.

Size the resistor to give the time constant with a
particular value
capacitor. The relay contacts are isolated and can be
connected to
your low voltage circuit.

The resistor should have sufficient wattage rating with
respect to the
current and the capacitor should be rated for at least
the maximum
voltage applied. ie 120v X 1.414. The relay can be
almost anything
with a suitable coil voltage. ie 100 - 120.

The circuit works by utilising the charging current into
the capacitor
to energise the relay. As the capacitor voltage
increases the relay
will drop out. The time difference between energising
and dropping out
is how long the annunciator will sound.

So I take it you'd like this circuit:
http://www.geocities.com/bonezphoto/...-shotBell2.gif

And now can you give us the R and C values to give, say, a
1- or 2-second on time? I don't know how to calculate such
things. (Understand how they work, just never learned the
actual math involved.)

I thought you learned that there should be a discharge path
for the capacitor unless you want to wait hours or days
before it will work a second time.

David