NE555 alarm circuit diagram

Published:2011/4/17 20:36:00 Author:Ecco | Keyword: alarm circuit | From:SeekIC

The alarm is composed of two parts of the transmitting and receiving. Transmitting circuit is shown in Figure 1. It consists of two vibration temperature circuits with different frequencies and they are composed of two 555 time-base circuits. When the two ends of CK are in short circuit, the first(IC1) 555 constitutes a low-frequency shock temperature circuit, the frequency F1 is mainly decided by C1, R2, the output frequency of pin 3 is the low-frequency signal of F1. When the output of pin 3 is in high level, the second (IC2) 555 constitutes a high-frequency shock temperature circuit, the frequency F2 is mainly decided by C3, R4, and F2 much higher than F1, so the output of pin 3 is the pulse modulated signal of F2. The modulation signal throughs the driving circuit composing of Q1, T1, C5, C6 and produces high frequency modulation pulse on the power line, the voltage of high frequency modulation pulse is decided by transmission distance.



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