On Tue, Nov 22, 2011 at 06:14:54PM -0500, Jay Ashworth wrote:
----- Original Message -----
From: "Matthew Kaufman" <matthew@matthew.at>
Indeed. All solid-state controllers, microprocessor or not, are required to have a completely independent conflict monitor that watches the actual HV outputs to the lamps and, in the event of a fault, uses electromechanical relays to disconnect the controller and connect the reds to a separate flasher circuit.
The people building these things and writing the requirements do understand the consequences of failure.
If you mean "an independent conflict monitor which, *in the event there is NO discernable fault*, *connects* the controller to the lamp outputs... so that in the event the monitor itself fails, gravity or springs will return those outputs to the flasher circuit", than I'll accept that latter assertion.
That protects against a conflicting output from the controller at the same time the conflict monitor completely dies (assuming its death is in a manner that removes voltage from the relays). It doesn't protect against the case of conflicting output from the controller which the conflict monitor fails to detect. (Which is one of the cases you seemed to be concerned about before.) -- Brett