| Electronics > Projects, Designs, and Technical Stuff |
| 'HV' switches voltage ratings: AC vs. DC |
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| TinkeringSteve:
Ok, while I do like the simplicity of "just cover the rotary switches mechanically", my mind wanders off anyway and so... went to this: Relays can't possibly switch without coil current being available, eh? And there are these things called bi-stable relays. I've sometimes seen them for bearable prices in one-off offers. So how about: - making one coil supply rail for all relays. - a analog watchdoggy circuit that looks whether that rail is on. - whenever that rail is on, it does BOOM on the circuit that shuts down the HV, which can only be activated again explicitly, and with the condition that, of course, the coil rail is detected to be OFF. So no changing of switch status is possible when HV is on. I guess I could simulate something similar with mono-stable relays with some parallel-out latch shift register that holds the on/off status bits, and some intercepting element that does not electrically allow passing through state-changes when HV is on. That would retain the vulnerability for the case that there is a defect, maybe one relay coil dying and going from ON to OFF state (if that is a failure mode that exists, I have no idea), or a sudden failure of the coil rail. For that, maybe, rare / unlikely occurrence, the coil supply rail total current could be monitored, and if that current changes -> HV OFF trigger. |
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