Electronic light timing circuit - has wide adjustable timing range using FET and Schmitt trigger switched by capacitance resistance timing circuit

摘要

A timing circuit is for applications, such as stair light or children's room light times switches. It consists of a capacitance resistance timing pair followed by a FET and Schmitt trigger stage. The timing may be adjusted over a wide range of up to 30 minutes. The timing circuit consists of a capacitance (6) and resistance (7) connected in series with a set of adjustment potentiometers (2,3,4,5) and a switch (1). This arrangement is connected to the gate of a FET (8) which is turned off when the switch (1) is actuated, for a period determined by the timing circuit. The FET feeds an output Schmitt trigger stage incorporating a transistor (14) and four resistors (10,11, 12,13).