actually debounce time should be on the other of 10ms, not 0.1ms

I know. But in this case, the contacts will be already closed or already opened. To be specific, the state of the contacts are tested once every 5 seconds (to save energy) and it is not important if, by coincidence, the sampling takes place at the very unlikely exact same time the relay is changing state. The next sample reading will be done well after the relay contacts have stabilized anyway.

The relay changes states only once every few hours, by the way.

 

I know. But in this case, the contacts will be already closed or already opened. To be specific, the state of the contacts are tested once every 5 seconds (to save energy) and it is not important if, by coincidence, the sampling takes place at the very unlikely exact same time the relay is changing state. The next sample reading will be done well after the relay contacts have stabilized anyway.

The relay changes states only once every few hours, by the way.

If you're only reading the switch once every 5 seconds, that's effectively a 5 second debounce.

You're good to go.

 

are you certain that the relay is switching? If dependent on an input, that input may be spurious, or conditional logic. PLC have modbus capabilities?, forget the hardware.

 

are you certain that the relay is switching? If dependent on an input, that input may be spurious, or conditional logic. PLC have modbus capabilities?, forget the hardware.

The reliability of the relay itself is not my responsibility. The customer is very much aware of that. What concerns me, is that my circuit reacts accordingly depending on the state of the relay, and as long as the relay is functioning within its own specs.

The control logic is extremely simple. There are no PLC's, modbus, nor any type of comms available.

 

Once in the eighties I was watching technician at vacuum implanter built on relay logics. Thus all the automatics was driven by 6 shelves each shelve a 24 raws of relays and each raw 48 relay long. Thus, the mis-actuting was a just norm. I was that technician learned well in wjich corner must be kicked by feet to program restore. The only cure was to sprinkle small amount of silicon grease soluted in large amount of alcohol. Ethylspiritus makses silver oxide reduction reaction, and silicon saves it against oxygen.

 

I may have missed the explanation, but I am wondering about the ultimate function that requires checking a relay status every few seconds when it changes only occasionally. What is the means of checking? OR, is the relay open or closed the actual logic input to some control scheme??If it is actually a voltage across the contacts then what sort of limits??

AND, is this a one-off system, or is this a standard product being sold to some market??