Circuit for overriding the cripple mode so that the relay remains latched

摘要

A plug presence sensor comprises an LED and a light sensor in the form of a photo-transistor which senses presence of a plug in a receptacle. The sensor is monitored by a microcontroller to control latching of a relay. The microcontroller de-energizes the relay, so that no power is present at the receptacle, when no plug is inserted. When the plug is inserted, then the microcontroller causes the relay to be energized to provide power to the receptacle. The microcontroller is preprogrammed to communicate with a remote master controller. In the event that a loss of communication occurs between the microcontroller and the master controller, the microcontroller automatically de-energizes the relay so that no power is present at the receptacle. A communication error output signal is connected to an override circuit including a capacitor which differentiates an edge of the communication error signal to inject a pulse onto the plug presence sensor signal which simulates removal and reinsertion of the plug. As such, the override circuit fools the microcontroller into thinking that a plug was removed and then inserted so that the relay remains energized to power the outlet receptacle.