The only reason the relays run on 24 volts is because I had a source for a large quantity of units with 24V coils. I've also found that 24V relays are easier to find than 12V. It really has nothing to do with the voltage being controlled.
Don
Interesting, and a basically GOOD idea.
>
> The use of a separate low voltage circuit to run power control devices
> such as relays is an industry standard. It's FAR safer in commercial
> machinery (where 220 and 440 volts is the common power circuitry), as
> the controls the operator actually touches are all low voltage (commonly > 24 volts).
>
> In your case, however, you are using the 24 volt control circuit to
> control a 12 volt power circuit ... rather the opposite of normal
> practice, but quite acceptable since ALL the voltages involved are low
> enough to be usually and relatively 'safe'.
>
> Dan Mitchell
> ==========
>
>
>
> Tra> >
> > >
> > >
> > > "KTØT" wrote:
> > >
> > > > :
> > > > : > But feedback from the DCC supply could also energize it. > > > > :
> > > > : I must be missing something here. ..... One set of stationary contacts
> > > > goes
> > > > : to the DCC supply. One set of stationary contacts goes to the DC > > supply.
> > > > The
> > > > : moving contacts goes to the track. There is absolutely no connection
> > from
> > > > : the DCC to the DC supply or to the relay coil.
> > > > :
> > > > : John H
> > > >
> > > > John, missing on this page is the original question as to whether a SPDT
> > > > switch would work safely. A SPDT switch would have one side of the > > output of
> > > > each supply connected together as well as a connection of some sort at
> > the
> > > > mains plug and grounds. Therefor, unknown and possible sneak circuits.
> > >
> > > He's probably thinking that the relay would be energized by an "accessory"
> > > output from the DC supply, one which turns on only when the DC supply is
> > on, and
> > > *not* from the DC supply's track output. This should be safe (but of > > course
> > > more trouble than the original poster asked about)..
> >
> > I run my relays from a separate 24V supply built from a cheap radio shack
> > transformer.
> > 24V relays are also easier to find than 12V.
> >
> > Keeping everything separate insures nothing can "feed back" through an
> > unsuspected common.
> >
> > --
> > snipped-for-privacy@prodigy.net
> >
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> > Don