"mick" wrote

Probably 90% of plug-in relays used for general purpose control are 24v
(AC & DC), 110vAC and 220/230vAC. You also find 12vDC used occasionally,
particularly in fire alarm applications. You won't often find 5v relays
with 3 or more contacts either.

You are being very specific here, limiting your scope to plug-in relays.
Most relays don't plug in, though clearly they are the type you are most
familiar with.

I wouldn't like to say "the vast majority, are PCB mount types".

If you look in the catalogues you'll find many PCB relays for every plug-in
one..

Likewise I'd disagree
with "their voltage and current ratings are well in excess of what might
be needed for this application

Yes, I was wrong to say voltage. Few currently available GP relays have an
adequate voltage rating for this purpose. However PCB relays are no worse
than plug-in types in this respect.


That might be ok. Running it with 350v takes it out of it's DC rating,
but you'ld probably get away with it if the load is about 200mA. It does
break the isolation rule of having 2 breaks in series though, as it's
only a single pole relay.


Is it single pole?, I didn't read the write up very carefully I'm afraid. I
just noticed that it had a 440V ac rating, wheras most relays have only a
250V ac rating.


That's fair enough. I'd originally understood (perhaps wrongly) that the
PSU had the HT going through the plug.

That was my understanding too. But from a safety POV it's the wrong approach
IMO.

That's how I built mine because I
wanted a modular PSU that I could use with alternative amplifier chassis.

Perhaps a better way still is to have a bracket holding the plug in. The
bracket has to be removed by undoing a screw. That would be ok even for
"stupid people". :-) It always annoys me that we can install a lump of
live copperwork in a steel cupboard, stick big warning notices all over
the door and yet still have to shroud the copper to IP2x (with more
warning notices) just in case someone is daft enough to ignore the
notices, open the door and stick their hand in without looking...
sizzle

Of course if you are building an amp and separate PSU for your own use you
don't *have* to do anything in particular in that respect. Just bear in mind
that you are responsible if anybody gets hurt.

David.