Protect PLC outputs against transients

Hi there,
I’m wiring a PLC with relay outputs (LM3109). Relay outputs have an on/off capacity of 2A resistance load.
I would like to protect the PLC outputs against transients, if necessary.
My questions are:

1) I want to connect 24VDC, 1A peristaltic pumps directly to PLC outputs. Should I connect a suppressor diode on the pump terminals?
2) Some PLC outputs are connected to power relays (JQX-13F coil power 0.9W). Should I also connect a suppressor diode on the power relay’s coil terminals?
3) There are other types of transient suppression. Is diode the most suitable in my case?
4) Which diode should I use (voltage and current)?

Thanks

1) I want to connect 24VDC, 1A peristaltic pumps directly to PLC outputs. Should I connect a suppressor diode on the pump terminals?

Click to expand...

Don't connect the pump directly to the PLC output, use an intermediate relay.

2) Some PLC outputs are connected to power relays (JQX-13F coil power 0.9W). Should I also connect a suppressor diode on the power relay’s coil terminals?

Click to expand...

It depends on how often you want to be called to site to fix problems, I like a peaceful life so I fit suppression to all relays.

3) There are other types of transient suppression. Is diode the most suitable in my case?

Click to expand...

See the attached (page 2) for information on suppression.

4) Which diode should I use (voltage and current)?

Click to expand...

I am not an expert on Diode ratings, I use 1N4004, they are over the top on current but sturdy enough to survive an industrial environment.

BryanG said:

Don't connect the pump directly to the PLC output, use an intermediate relay.

It depends on how often you want to be called to site to fix problems, I like a peaceful life so I fit suppression to all relays.

See the attached (page 2) for information on suppression.

I am not an expert on Diode ratings, I use 1N4004, they are over the top on current but sturdy enough to survive an industrial environment.

Click to expand...

Thanks a lot, Bryan!! I'll do as you said.
Cheers!