The multi-functional portable dual-way alarm circuit

Published:2011/7/6 8:47:00 Author:qqtang | Keyword: multi-functional, portable, dual-way alarm | From:SeekIC

This circuit consists of two parts, the upper limit alarm function is composed of A, B, R4 and C1, and C, D, R5 and C2 form the lower limit alarm function, see as figure 1. Usually, there are two alarm spots, the upper and lower, which are fixed in RP1 and RP2 respectively, which make the input terminals of A and C both in a high LEV, and both of them output a low LEV so the oscillators stop. When it is too hot outside, the resistance of the thermistor is falling down, which makes A output a high LEV, B is starting to oscillate, and the piezoelectric pottery chip YD is generating the bumming sound of high frequency. At the same time, LED1 is glowing, indicating that the temperature is too high.



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