serious issue

The relay coil currents or opt input relays currents are the only touchy part.  Less components needed with opto relays but latching functions may be a problem. Most of these functions are pulsed output into another latching end-device that remembers where it is put. eg: 240 kv breaker. It stays open or closed after operating.
 
On top of all that the end-device always has an extra contact that is tied back into status and verifies the complete process from the end-device  back to the human and machine located remotely. Mostly separate channels of data except for comm lines.
 
On the WC32 IO board that Ross working with us, there are four channel high current output driver IC. 
For WC8, Ross might be able to make a relay driver daughter board for your needs.
 
I thought for the requirement is so strict that you would monitor relay output to feedback, so that if the action did not taken place on the secondary side , you would stop and alert operator.  If your relay has a pair spare contact, that could be used to feedback, or even monitor the device being connected through relay to make sure it turned on.
 
If you are doing anything that is genuinely likely to result in serious injury or death, relying on a second set of relay contacts is not really "good enough".
It might be enough to tell you that the relay has physically operated, but it won't tell you if the (primary) contacts have fused closed, or burned out.
In that case, actually monitoring the voltage presented to the output is the only really sure way to know.
 
rossw said:
If you are doing anything that is genuinely likely to result in serious injury or death, relying on a second set of relay contacts is not really "good enough".
It might be enough to tell you that the relay has physically operated, but it won't tell you if the (primary) contacts have fused closed, or burned out.
In that case, actually monitoring the voltage presented to the output is the only really sure way to know
Click to expand...
 
yes absolutely. It would make sense mating a control with a quality assurance board. Given devices are controlled digitally, we could query them about their status.  may be the first step into that direction could be a one wire photo mos relay allowing check of the switched line?
 
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