报(bao)警器(qi)电路图

如图所示为电(dian)源电(dian)压高、低限(xian)报警(jing)(jing)(jing)(jing)电(dian)路(lu)(lu)(lu)(lu)。该报警(jing)(jing)(jing)(jing)器由(you)高限(xian)报警(jing)(jing)(jing)(jing)电(dian)路(lu)(lu)(lu)(lu)和(he)低限(xian)报警(jing)(jing)(jing)(jing)电(dian)路(lu)(lu)(lu)(lu)两(liang)部分组(zu)成。右侧为低限(xian)报警(jing)(jing)(jing)(jing)电(dian)路(lu)(lu)(lu)(lu)：在电(dian)源电(dian)压接(jie)近低限(xian)(但仍为正常)情况下，调节电(dian)位器Wz，使556 8脚电(dian)位稍大(da)于1/3VDD。

当电(dian)(dian)源电(dian)(dian)压向下偏移使⑧脚(jiao)(jiao)电(dian)(dian)位降到小于(yu)l/3VDD)时，556 ⑨脚(jiao)(jiao)便发生翻转，输出高电(dian)(dian)平(ping)(ping)，从而使低(di)限告警发光二极管(guan)(guan)LED2发光。同(tong)时，因晶(jing)体管(guan)(guan)BG与⑨脚(jiao)(jiao)相连，故(gu)管(guan)(guan)子饱和导通，相应又使8脚(jiao)(jiao)钳(qian)位于(yu)低(di)电(dian)(dian)平(ping)(ping)。

稳压(ya)(ya)(ya)管Dw的稳压(ya)(ya)(ya)值应选择(ze)为稍(shao)低(di)于2/3VDD值。左侧(ce)为高(gao)限报警电(dian)(dian)(dian)路(lu)(lu)：调节电(dian)(dian)(dian)位器W1，使电(dian)(dian)(dian)源电(dian)(dian)(dian)压(ya)(ya)(ya)在(zai)接近高(gao)限电(dian)(dian)(dian)压(ya)(ya)(ya)(但仍为正(zheng)常(chang))情况(kuang)下，556⑥脚(jiao)电(dian)(dian)(dian)位稍(shao)高(gao)于l／3VDD值，此(ci)时左侧(ce)电(dian)(dian)(dian)路(lu)(lu)输(shu)出(⑤脚(jiao))为低(di)电(dian)(dian)(dian)平。当电(dian)(dian)(dian)源电(dian)(dian)(dian)压(ya)(ya)(ya)瞬间升高(gao)时，因C1两端电(dian)(dian)(dian)压(ya)(ya)(ya)不(bu)能突变(bian)，即C，的电(dian)(dian)(dian)压(ya)(ya)(ya)相对于556的基准电(dian)(dian)(dian)压(ya)(ya)(ya)(1／3VDD)变(bian)低(di)，则电(dian)(dian)(dian)路(lu)(lu)发生(sheng)翻(fan)转(zhuan)，⑤脚(jiao)输(shu)出为高(gao)电(dian)(dian)(dian)平，此(ci)时高(gao)限告警二(er)极(ji)管LED1发光，告知超限。

图中A为复(fu)位(wei)开(kai)关。按下时，强(qiang)制复(fu)位(wei)，使电路(lu)输出(chu)低电平。本(ben)电路(lu)适用于在电源电压波动时及时发光报警、进(jin)行监视，从而保证(zheng)直(zhi)流电压稳定度比较高的场合。

报警器电路图