Re: SS Relays - Revisited

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "cutthroatplasmaco"
<cutthroatplasmaco@y...> wrote:

> Thanks guys, I'm pretty sure i understand this now. One last
> question, Would an automotive relay be acceptable and safe to use

in

> this situation? I've seen this mentioned (actually I think someone
> suggested it in reply to a previous question i posted). The reason

I

> even went with the SSR was that it was my understanding that an SSR
> is an isolated relay... I don't really know if that even matters,

but

> it sounded good at the time. If the automotive relay is not an
> acceptible device, then I think I'll just try to order the relay
> board from Bob and Jim.
> Thanks,
> Chris

Any small 12DC relay with at least one set of NO contacts will work.
RS has them. Surplus dealers like www.MPJA.com or www.BGMICRO.COm
have them for close to nothing. Most likely the switches on your
plasma torch activate a standard relay on the logic card inside the
unit. Automotive relays are made to carry large currents and usually
need a larger activation current to operate. The relays we are
talking about are not much bigger than an IC and made to handle
millions of operations at low current. They are sealed (another good
thing to have in the plasma world). The torch activate is just a low
current signal that drives an opto isolator or small relay. All of
the heavy switching is done by internal circuitry. You are just
putting another switch in parallel with the torch switch. Isolation
on any relay is extremely high since its like flicking a lightswitch
with a 12" wooden ruler!