| 摘要 |
PURPOSE:To prevent a human accident caused by a fact that a lamp lighting AC is applied to a manual operating part by cutting off electrically a transfer of a signal of an exposure control signal input part and a dimming circuit by use of an optical coupler. CONSTITUTION:When an operator indicates an exposure quantity control value by moving a variable resistance, it is inputted to terminals 25, 26 of a dimming circuit as a pulse wave whose duty and period are varied. By this pulse wave, a light emitting diode 24 emits light, a phototransistor 23 receives light, and a pulse element 9 is turned on and off. In this way, conduction of a primary winding 8 of a pulse transformer is controlled, and an AC control element 2 is turned on and off through a secondary winding 4 of a pulse transformer. In this way, a phase angle of a point of time when a current flows to a lamp 1 is controlled, and the intensity of illumination is adjusted. Since the operating part of a man is cut off from an AC power source of the lamp, the safety standard to an electric appliance of the circumference is satisfied. |
