The school bell timing circuit diagram

Published:2011/4/10 20:20:00 Author:Ecco | Keyword: school bell timing | From:SeekIC

General school bell is pulled by the people, but it is difficult to control the tone time. It can solve this problem by installing a timer to control ring. Working principle is shown in Figure 213: To press the button QA when pulling the bell, the time relay SJ pulls, bell ring tone is also energized, to release the button QA, as the SJ pulls, SJ normally open point is self-hold until time relay seting time(time relay could adjust to 1 minute or according to the choice), the delay normally closed point is cut off and make time relay loses electric and releases, SJ normally open point is cut off, the tone will stop.



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