夜间从石英钟辨认时间,人们都甚感不便。若给石英钟增加一个小光源,不仅能在夜间看清时间,而且还能起到装饰作用,可谓一举两得。本文介绍一种石英钟夜间指示电路,它能够在白天闪烁发光,模拟出石英钟秒针的走动,到了夜间便转换成常亮状态,以助人们认清时间。本电路简单,适台家庭制作,广大电子爱好者也不妨一试。电路原理该自动指示电路如附图所示。电路由光控电路和振荡电路两部分构成。光敏晶体管BG1用来检测环境的光线强度,当环境光线很弱时,BG1处于高阻状态,BG2因无偏置电流而截止,BG3则导通。由BG4、BG5组成振 People find it inconvenient to recognize time from a quartz clock at night. If the quartz clock to add a small light, not only to see the time at night, but also play a decorative role, can serve two purposes. This article describes a quartz clock night indication circuit, which can shine during the day and simulate the movement of the quartz clock second hand, the night will be converted into a permanent light state to help people recognize the time. The circuit is simple, suitable for Taiwan family production, the majority of electronic enthusiasts may wish to give it a try. Circuit Theory The automatic indication circuit shown in the figure. Circuit consists of light control circuit and the oscillation circuit is composed of two parts. Phototransistor BG1 is used to detect ambient light intensity. When the ambient light is weak, BG1 is in a high impedance state, BG2 is turned off due to no bias current, and BG3 is turned on. By BG4, BG5 form vibration