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夜间在室内干活,突然遇到停电,这时若能有一点亮光作照明,你就不会因在漆黑一团的房子里而感到不知所措。本文介绍一种由两节1.5V 电池供电、发光二极管作光源的应急照明灯。电路原理:该小型应急照明灯电路原理如图1所示。B1电池(3V)正极通过开关 S1接到三极管 Q2发射极。通常,有外光源照射在光敏电阻 R1上,其阻值较小,与 R5分压使 Q2基极电位较高,Q2截止;当没有外光源照射在 R1时,其阻值增大,与 R5分压使 Q2基极电位下降,Q2导通,LM555(IC)定时器得电起振,
Working indoors at night, suddenly having a power outage, and at this moment, if there is a little bit of light for lighting, you will not feel overwhelmed by the dark house. This article describes a two 1.5V battery-powered, light-emitting diode light emergency lighting. Circuit Theory: The small emergency lighting circuit shown in Figure 1. The B1 battery (3V) is connected to the emitter of transistor Q2 via switch S1. Generally, there is an external light source on the photosensitive resistor R1, its resistance is small, and R5 partial pressure so that the Q2 base potential is higher, Q2 off; when no external light source in the R1, the resistance increases, and R5 Partial pressure so that the base potential of Q2 decreased, Q2 conduction, LM555 (IC) timer was energized,