According to Tom Gardner :

[ ... ]

guns. I need to delay the fixture at the top of the stroke long enough to
fire the guns.

A few tenths of a second should be enough. An off-delay timed relay should
do it, right? As I look through the Grainger catalog and McMaster-Carr I
get a bit confused.

First off -- if your relay controls are DC powered and not AC
powered, there are relays from old phone systems which would serve you
well. The normal relay has one or two coils wound on the center soft
iron core (about 3" long IIRC), and that one is quick both in pick and
in release. The ones which I am describing below were made by Automatic
Electric and Claire -- among others.

Then you take one of the two-coil ones and replace one of the
coils with a slug of copper occupying the same space. If the copper
slug is closer to the moving arm of the relay, it will be slow to pick,
and only slightly slow to release.

If the copper slug is closer to the base of the relay, then it
will be only slightly slow to pick, but quite slow to release, which is
what you want.

Ones made to be slow in both have the copper as a thick-walled
sleeve around the core with the winding around that.

Now -- there are other ways to do this. That copper slug is a
shorted turn. You can get some of the same effect (a bit less delay) by
putting a short circuit across the terminals of a second coil -- at the
base if you have a choice. And to make it still as quick pick up but
slow release, use a spare pair of contacts to short the second coil's
terminals only once the relay has actuated.

Or -- you can connect a capacitor across the coil's windings,
with a diode to isolate it from the control power when the relay turns
off. (Again, you need DC relays for this.)

Or -- get a relay with a dashpot which can either be slow to
pick or slow to release, depending on the design. Those can be DC or AC.

What is a "Off delay Retrigerable, one shot" relay? I don't think that this
is what I want but I'm not sure. I think I want just an "Off Delay" relay.

That is an electronics description of the behaviour which you
want. It will need steady power independent of the control signal. The
"one shot" is a circuit which goes through its time cycle once per input
pulse. The real question is whether it can be adjusted to turn off
quickly enough so it does not slow your production.

Good Luck,
DoN.
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