Digital long delay circuit

Published:2011/4/20 9:10:00 Author:Nicole | Keyword: digital, long delay | From:SeekIC

Ordinary long time delay circuit is usually with the help of electrolytic capacitor or high impedance circuit. This circuit has poor stability, and the accuracy of delay also is not high. Here is a digital long delay circuit, it casts behind the electrolytic capacitor and high impedance circuit absolutely, the accuracy of delay is high. The core of this circuit is the integrated block MC14521B, it is a 24 class clock division circuit, it contains inverters which composed of oscillation circuit. If the trigger input terminal is grounding or without signal, then the circuit is into delay state, the delay time is adjusted by the range switch X and 100KΩ potentiometer. If X is connected to point A, the delay time is from 1 minute 40 seconds to 18 minutes 30 seconds, if X is connected to point B, the delay time is from 13 minutes 20 seconds to 2 hours 28 minutes. If X is connected to point C, the delay time is from a hour 47 minutes to 20 hours. The specific delay time is set by 100KΩ potentiometer. If it needs longer delay, you can use bulky capacitor insteads of 39nF capacitor. Then the delay time will reach more than one week. Added a positive signal on the trigger input terminal, the divider in 4521B can be reset. The delay is reliable and steady, it can use 6~15V regulated power supply. The prototype adopts 12V power supply.



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