US Patent 10440827 Programmable logic controller override

An override board of a programmable logic controller includes a manual switch such as a push button for manual selection between a first “auto” mode where the output is controlled by the programmable logic controller, a second mode where the output is energized, and a third mode where the output is de-energized. The override board can be switched back to the “auto” mode electronically, without physically obtaining access to the controller and without moving the manual switch. The override clear signal is preferably provided on a power connection with the programmable logic controller and to a microprocessor on the override board which controls the output mode.