that is exactly what i've been saying.

 

that is exactly what i've been saying.

When the ULN2003 arrived on the scene 40 years ago, it had the diode built in!

 

yes, and things changed a lot in 40 years. modern ICs pack way more punch. for example
https://www.infineon.com/dgdl/Infin...N.pdf?fileId=db3a304320d39d590120f700bb736a89

 

yes, and things changed a lot in 40 years. modern ICs pack way more punch. for example
https://www.infineon.com/dgdl/Infin...N.pdf?fileId=db3a304320d39d590120f700bb736a89

One great thing about AAC is learning about new ICs that I would never have thought to look for.

 

this is a public forum and everyone is entitled to their opinion.
... snip ...
btw. why stop at one interposing relay per output? you can have several of them driving each other. if you play your cards right, you can get kickbacks from the relay company

I came here to ask a question about a flyback diode on the coil of a contactor and the thread was rapidly hijacked into why suppression was required across the load. The signal to noise ratio made it hard to figure out the answer to the original question.

Anyway, I have finished my design. Thanks to all who replied.
P.S. no kickbacks sought or required.

 

I would not say it was "rapidly highjacked" , you just received some varying opinions?
BTW, I have experienced interference from a solenoid that shut down a system, and the offender was galvanically isolated from the operating unit.

 

i see no reason for confusion but if there was a concern or trouble following discussion...why not just ask for clarification? the point of the topic is to help answer questions, it is your topic so feel free to participate.

btw. the "inductive load" in this context was the contactor coil itself (and not the device that contactor is controlling).
for inductive load suppression is usually needed, recommended and it was stated where it is best to add it.

one way to get more precise answers is to ask questions that are very specific. for example in this case why not include model name of the output card, exact model of the contactor, schematics of the circuit etc.?

 

why suppression was required across the load.

Actually, it's quite important to know whether the suppression should go across the driver or across the load.

 

the very first response includes info and screenshot from the manufacturers webpage with sample range of suppression devices. and they are designed to fit directly onto contactactor coil... one just need to read the catalog or product selection guide. that is an important step of industrial automation design process.

 

Some PLC output modules were intentionally made to switch a bit slower so as to reduce that possible inductive spike. I am not sure if that is still done or not, but it was very handy.