應急燈自動充電器的設計制作
用6V免維護電瓶供電的應急手提燈在農村應用非常廣泛,其配用的充電器是一個變壓器降壓、單二極管半波整流裝置,充電時間很難掌握。由于電池虧電或過充電往往會造成電池壽命縮短,本人設計制作了一個簡易自動充電裝置,可有效延長電池壽命。
電路如圖1所示。GB為待充電電瓶,平時只要不再使用,就將充電器插頭X1、X2插入手提燈的充電插孔內。按一下啟動按鈕SB,220V交流市電經保險Fu、SB加在電源變壓器T1初級。其次級輸出兩路交流電壓:交流12V經VD1半波整流、C2平滑濾波,使VT導通。繼電器K1吸合,K1-1閉合。此時松手使SB斷開后,充電器仍然工作。圖中,R2是VT的偏置電阻;C1是降壓電容,LED1(紅)為市電電源指示管;啟動完成后,交流9V電壓經VD2整流為電瓶GB充電,LED2(綠)為充電指示管。隨著充電過程的進行,電瓶兩端電壓不斷上升,當升至極限電壓值(約7.5V)時,穩壓管VD3反向擊穿導通,光耦合器4N25①、②腳內發光二極管發光,④、⑤腳內光電管受光后隨之導通,VT基極被下拉(約0V)而失去正偏壓,所以VT截止,K1釋放使K1-1斷開,充電器停止充(chong)電(dian),充(chong)電(dian)指示管LED2熄滅。
元件選用與制作
T1可(ke)使(shi)用(yong)10VA左右(you),次(ci)級有9V和(he)12V輸(shu)出的(de)電(dian)(dian)(dian)(dian)源變(bian)壓(ya)(ya)器(qi)(qi)(qi),若(ruo)使(shi)用(yong)原配變(bian)壓(ya)(ya)器(qi)(qi)(qi)(次(ci)級輸(shu)出9V)時,繼(ji)電(dian)(dian)(dian)(dian)器(qi)(qi)(qi)K1工作電(dian)(dian)(dian)(dian)壓(ya)(ya)也應選9V。繼(ji)電(dian)(dian)(dian)(dian)器(qi)(qi)(qi)選用(yong)4088、4089、JRX-13F等12V繼(ji)電(dian)(dian)(dian)(dian)器(qi)(qi)(qi)。VT使(shi)用(yong)9013、9014、8050等小(xiao)功率晶(jing)體管,要(yao)求穿(chuan)透電(dian)(dian)(dian)(dian)流(liu)要(yao)小(xiao),開(kai)關(guan)特性好,β=100~1500光耦合器(qi)(qi)(qi)IC可(ke)用(yong)4N23、4N25、4N33等型號。C1的(de)耐壓(ya)(ya)不得小(xiao)于(yu)450V,容量取(qu)220nF~470nF,容量越(yue)大,LED1越(yue)亮。調試時,先(xian)斷開(kai)VD2,在(zai)X1、X2兩端加7.5V直流(liu)電(dian)(dian)(dian)(dian)壓(ya)(ya),從(cong)大到小(xiao)調電(dian)(dian)(dian)(dian)位(wei)器(qi)(qi)(qi)RP,使(shi)4N250⑤腳電(dian)(dian)(dian)(dian)位(wei)突然下降(K1釋放)即(ji)可(ke)。