美國邦納Banner光電開關的亮控制

在夜(ye)(ye)(ye)間(jian)，城市許多地方（如道(dao)路(lu)施(shi)工場(chang)(chang)地）或野外作(zuo)業施(shi)工的單(dan)(dan)位(wei)，都需(xu)要(yao)在施(shi)工現場(chang)(chang)安(an)裝(zhuang)指示(shi)燈，以保證(zheng)夜(ye)(ye)(ye)間(jian)行人及(ji)行車的安(an)全。自控(kong)夜(ye)(ye)(ye)間(jian)閃(shan)光(guang)指示(shi)燈，便(bian)具有(you)白天自動(dong)關閉而(er)夜(ye)(ye)(ye)間(jian)又自動(dong)開啟閃(shan)光(guang)、指示(shi)的功能。電(dian)(dian)(dian)路(lu)簡單(dan)(dan)、安(an)裝(zhuang)容易、工作(zuo)可靠。當一(yi)定波(bo)長的光(guang)照(zhao)射到BG1的基極時，便(bian)產生(sheng)光(guang)電(dian)(dian)(dian)流，使(shi)BG2管(guan)基極處低電(dian)(dian)(dian)位(wei)而(er)截止，BG2管(guan)集電(dian)(dian)(dian)極處高電(dian)(dian)(dian)位(wei)，BG3管(guan)導(dao)通，繼電(dian)(dian)(dian)器J得電(dian)(dian)(dian)動(dong)作(zuo)，實現了光(guang)電(dian)(dian)(dian)開關的亮(liang)控(kong)制。

目前(qian)，為整(zheng)頓城市市容，美化城市面貌，都在(zai)搞穿(chuan)過公路(lu)敷設地(di)下(xia)電(dian)(dian)纜、地(di)下(xia)排水溝(gou)等工(gong)程建設，這樣必需在(zai)路(lu)面上開(kai)溝(gou)挖槽，若不安(an)裝施工(gong)指示燈，將給車輛行駛帶來很大危險，因此施工(gong)現(xian)場都裝有安(an)全信號(hao)(hao)燈。是由220V市電(dian)(dian)經電(dian)(dian)容降壓的夜間(jian)光電(dian)(dian)開(kai)關(guan)信號(hao)(hao)燈電(dian)(dian)路(lu)。220V市電(dian)(dian)經電(dian)(dian)容C1降壓、D1～D4橋(qiao)式整(zheng)流和DW穩(wen)(wen)壓后，向光電(dian)(dian)開(kai)關(guan)電(dian)(dian)路(lu)提供穩(wen)(wen)定的9V直流電(dian)(dian)源(yuan)。

白天在強光(guang)作(zuo)(zuo)用下(xia)光(guang)電開(kai)關(guan)阻(zu)斷(duan)，由時基電路NE555構(gou)成(cheng)的(de)振(zhen)蕩(dang)器，因(yin)電路無(wu)(wu)電源(yuan)電壓不(bu)能工作(zuo)(zuo)，雙向可控硅(gui)(gui)SCR1無(wu)(wu)觸(chu)發電流而處于關(guan)斷(duan)狀態(tai)(tai)，紅色信號燈ZD不(bu)亮。當進(jin)入夜晚，BG1因(yin)無(wu)(wu)光(guang)照，使光(guang)電開(kai)關(guan)處于通的(de)狀態(tai)(tai)，NE555等組(zu)成(cheng)的(de)振(zhen)蕩(dang)器工作(zuo)(zuo)，腳便不(bu)斷(duan)地(di)輸(shu)出(chu)超低頻(pin)矩形脈沖，觸(chu)發雙向可控硅(gui)(gui)SCR1不(bu)停(ting)地(di)導通與(yu)關(guan)斷(duan)，使信號燈一(yi)閃一(yi)閃地(di)發亮。

在白天，光(guang)敏二極(ji)(ji)管(guan)(guan)D2因受光(guang)照呈低電(dian)阻，BG管(guan)(guan)基(ji)極(ji)(ji)電(dian)位下降，使(shi)BG截止(zhi)，電(dian)阻R1上(shang)無(wu)電(dian)壓(ya)輸(shu)出，故雙向可(ke)控硅SCR處于關斷(duan)狀態(tai)，燈泡ZD不亮(liang)。當夜(ye)幕降臨(lin)時，D2因無(wu)光(guang)照其暗(an)阻增(zeng)大(da)，使(shi)BG基(ji)極(ji)(ji)電(dian)位升高而(er)導(dao)通，R1上(shang)輸(shu)出的電(dian)壓(ya)觸發可(ke)控硅SCR導(dao)通，路燈得電(dian)點亮(liang)。調(diao)節電(dian)位器(qi)W，可(ke)調(diao)節BG基(ji)極(ji)(ji)電(dian)位高低，即調(diao)整了光(guang)控的靈敏度。  在安裝時，光(guang)敏二極(ji)(ji)管(guan)(guan)D2應加有(you)防(fang)雨(yu)的透明玻璃(li)罩，且(qie)安放在能全天被日光(guang)照射的地方(fang)。D2也可(ke)用光(guang)敏電(dian)阻或(huo)光(guang)敏三極(ji)(ji)管(guan)(guan)。