Inter posing relay 5

[Indy]

Hi,
With regards to a Siemens DO card which has outputs rated 0.5A@24VDC if we are using these output channels to power 24VDC solenoid valves (0.3W &7w)would these require interposing relays as they are within the limits of the channel?

Thanks

 

[danw2]

Apparently Keith and I run into more 'bottom feeders' than others. I also always opt for interposing relays for the same reasons Keith and Jeff cite.

 

[thebard3]

Danw2--
Don't go there. A couple of weeks ago I received a call about a problem at the plant. I was pretty sure I knew what it was and called the electrician to check it out. He reported back that everything I had him check was fine so I had to go in. I discovered that he was looking in the wrong control panel.

Brad Waybright

The more you know, the more you know you don't know.

 

[RedSnake]

In my experience savvy customers can change relays but not PLC cards.

danw2 then you are using the wrong PLC cards, the ones we have used for the last twenty years, you exchange as easily as a relay it's just plug and play.

But we never have to. ;-)

/A

“Logic will get you from A to Z; imagination will get you everywhere.“
Albert Einstein

 

[FreddyNurk]

I've seen the same argument for using additional terminals beyond PLC cards as the maintenance gibbons onsite somehow manage to break the PLC cards, so providing terminals helps prevent that, but I suspect that the overall consideration is a little more nuanced than that.
There have also been improvements in automation equipment over the years that make replacement easier (pluggable terminals for each PLC card as an example), and there's also the cost, both in equipment and assembly for the panels to include the additional relays. My preference is generally additional relays, as it's then possible to run with a single type of output card, and everything else gets interposing relays or equipment suitably rated to drive whatever's at the other end.

EDMS Australia

 

[jraef]

LOL... "maintenance gibbons "...

I use the term "Bubba". In my experience the worst maintenance tech in any given facility is invariably named (or nicknamed) Bubba. He has no neck, hands like meat hooks, fingers like sausages and a brain like Emmantaler cheese.

This guy is a Bubba...

" We are all here on earth to help others; what on earth the others are here for I don't know." -- W. H. Auden

 

[RedSnake]

I have only come across one like that during my years, but his nickname was like "weld guru" and he was actually good at his job and he made great sponge cake.

/A

“Logic will get you from A to Z; imagination will get you everywhere.“
Albert Einstein