Frost Alarm Circuit (2)

Published:2011/5/12 2:19:00 Author:Robert | Keyword: Frost, Alarm | From:SeekIC

The forst alarm circuit introduced in this example can give the sound and light signal immediately when the frost coming to remind the workers to prepare for anti-frost in time. This device can be widely used in the areas such as agriculture and mining and so on.The circuit's working principle is shown below.This frost alarm circuit is made up by the frost detecting circuit and sound-lignt alarm circuit which is shown in the picture below. The frost detecting circuit is made up by the thermistor RT, resistance R1~R3, potentiometer RP, capacitor C and operational amplifier integrated circuit IC1.The sound-light alarm circuit is made up by resistance R4, R5, transistor V1, V2, alarm alarm indicator lamp HL, sound effect integrated circuit IC2 and speaker BL.When there is no frost, the atmospheric temperature is relatively higher. RT is in low-resistance mode, IC in-phase input port's voltage is higher than the out-phase input port's, and it outputs high voltage level to make V1 and V2 disconnected. So HL does not light and IC2 does not work, BL has no sound.In case of the frost coming, the atmospheric temperature is low and the RT's resistance would rise to make the IC's out-phase input port voltage higer than the in-phase input port's voltage and make its output port's voltage be low voltage level. So V1 and V2 is connected and HL would light, IC2 is electrified to work and BL would have the alarm sound.



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