One contact, two circuits 1

[enkwizative]

Is it ok to use one contact for two different circuits, with two different power supplies, as indicated?

thanks

 

[ScottyUK]

"Maybe".

Electrically it will work as drawn, but there are other questions which arise when you common up the two power supplies which we can't answer based on the information given, like isolation and protection.


----------------------------------

If we learn from our mistakes I'm getting a great education!

 

[VEBill]

If the existing power supply has enough current to run both "alarm modules", then you might simply eliminate or ignore the temporary power supply and wire the "alarm module" inputs in parallel.

But there's not quite enough info to be sure.

 

[waross]

What Scotty said. In the event of a problem the interconnected supplies may lead to a more serious issue rather than a simple shutdown.
Most of us would not do so. If we were tempted, we would not attempt it without more information than you have provided.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[Henneshoe]

If your power supplies are not perfectly balanced, some amount of current is going to flow through your alarms. At a minimum, I would put a diode in the hot leg of each power supply to ensure current isn't flowing the wrong direction.

 

[waross]

Good call Henneshoe;
Some devices are intolerant of reverse current.
Ripple may also be an issue.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[enkwizative]

thanks for the replies guys. i voiced these concerns with the engineer and we'll redesign it. i'm looking at separating the circuits and using an interposing relay.