Time switch with two time periods and power settings - has first full power triac circuit followed by second period half power thyristor setting

摘要

The time switch control is for a.c. powered equipment with one or more switches, e.g. automatic control of lights on a staircase. The appliance (lamp 1) is controlled for two time periods, the first at full power and the second for safety purposes at reduced power and brightness. The primary circuit is full wave through a triac (6) controlled by the first time control circuit (8) after the main switch (22) has been operated. After expiry of the first time period, the triac is switched off and the second time period started by connecting the control lead (18) of the half wave thyristor (19) to a time control output (13) and switching it on (thyristor 19). A second circuit is given using a third time period and employing multivibrators and flip-flops.