Staircase lighting time delay circuit - uses relay and electronic time with pushbutton operated override to save electricity

摘要

The time delay circuit for switching off staircase lighting on several floors, uses a relay (Re1) for the switching off operation, which can be overridden by operating a push button (Dr) for a second time. This ensures that the lights (L) are switched off sooner, to save electricity. The push button bring into operation a transistor (T.) in series with a capacitor (C2) and diode (d4) which excite the relay coil with a pulse of about the same time duration to override the relay. In series with the relay is a thyristor (Thy) connected to the capacitor (C2). An integrated circuit (JC) is used to control the time during which the relay maintains current to the lights. This forms an oscillatory circuit with further components (R8, R7,C4,P) to obtain a frequency for a divider which provides a lower frequency signal.