The power failure alarm circuit

Published:2011/9/18 20:56:00 Author:Ecco | Keyword: Power failure , alarm circuit | From:SeekIC

Sometimes, when the power is black out for some reasons, it needs to alarm automatically to inform people overcoming the breakdown as soon as possible. Figure 185 shows a power failure alarm. When power supply works normally, ZJ contactors pull in, so that the ZJ normal closed contact cuts off, then power is charged by the electrolytic capacitor C1 between the lights XD and diode D. When the power is black out for some reasons, ZJ contactors release, so that electrolytic capacitor C1 discharges to the sound and light alarm circuit, neon light bulbs turn on, speakers emit alarm signals, the alarm time is 5 to 6 minutes.



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