| 摘要 |
PURPOSE:To enable to obtain constant visual recognizability regardless of brightness of the surroundings by a method wherein a photo transistor and a visible light emitting diode are connected in series. CONSTITUTION:The circuit is formed in a structure wherein a power source 1, a protection resistor 2, the photo transistor 3, and the visible light emitting diode 4 are connected in series. When the voltage of the power source 1 is kept adjusted so that an appropriate fixed current flows in case of surroundings in normal brightness, the photocurrent flowing to the photo transistor 3 increases in proportion to the brightness in case of surroundings brighter than normal brightness, and thereby the current flowing to the visible light emitting diode 4 increases, then it shines brightly. In case of surroundings darker than normal brightness, since the photo current in proportion to the decrease of surrounding light flows to the photo transistor 3, the current flowing to the visible light emitting diode 4 decreases, and accordingly it shines darkly. The use of a light emitting diode which increases brightness in proportion to current enables the brightness of the visible light emitting diode 4 to vary in proportion to the brightness of the surroundings, resulting in constant visual recognizability to the surrounding brightness. |
