| 摘要 |
PURPOSE:To increase the utility of a room lamp to be lit at the opening of a door and turned off at the closing by gradually decreasing the electric current on the basis of a CR time constant circuit for dimming after a door switch is turned off. CONSTITUTION:When a door is opened, a door switch 1 is closed to turn on a door indicator 4 and a room lamp 3, while at the same time, the electric charge of a condenser C2 of a time constant circuit 61 is discharged by the door switch 1 via a resistance R2 and a diode D3 to reset the time constant circuit 61. When the door is closed, the door switch 1 is opened to send electric current to the condenser C2 of the time constant circuit 61 of a dimming circuit 6 via the door indicator 4 and a diode D2 for charging. At this charging, a transistor Q3 is on via transistors Q1 and Q2, and the room lamp 3 is maintained to be lit. As a terminal voltage V1 of the condenser C2 is increased, the current flowing through a collector of the transistor Q3 is decreased, and the lamp 3 is gradually dimmed. |
