On Wednesday 12 April 2006 19:56, I.F. wrote:
An easy way to make a time delay is with a long tailed pair of transistors
like a differential amplifier stage and add a high value cross coupling
resistor so it acts as a Schmidt trigger and avoids relay chatter. Connect
one base to a zener about half the voltage of the secondary rail used and
the other base to a potential divider shunted by a time delay capacitor -
don't forget a discharge diode from the capacitor to Vcc, this ensures that
as Vcc falls below 1/2 value at switch off it discharges the cap. A relay
driver transistor tapped off the collector resistor of the Schmidt output
transistor completes the line up of only 3 transistors, be sure to remember
also the back emf diode on the relay coil, the relay of course must provide
adequate isolation between primary & secondary supplies!

I have a circuit in use which is sensitive to relay chatter, so anything better
is welcome.

My circuit design skills are somewhat limited (I really need to work on it), so
I can't completely follow what you mean. Especially the LTP, I never really
understood how they work. Could you draw up a schematic? You can post images
to www.imageshack.us, should you be unable to send attachments. Thanks in
advance.