Crop anti-frost circuit

The frost alarm introduced in this example can send out an audible alarm signal when the ambient temperature is lower than 1°C to remind farmers to prepare for frost in time.
    (1) Circuit composition The frost alarm circuit consists of a power supply circuit, a temperature
detection control circuit and an alarm circuit , as shown in Figure 8-19. The power circuit consists
    of battery GB, power switch S and electric hot spot thermometer Q.
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    The alarm circuit is composed of a sound integrated circuit IC, a resistor, a resistor, a transistor
VT and a speaker Y.
    (2) Circuit principle: After turning on the power switch S, the alarm circuit enters
the alert state. When the ambient temperature is higher than 1°C, the electric heating control contact of Q is in
a disconnected state, the alarm circuit does not work, and Y does not sound. When the ambient temperature
drops to 1°C, the electrothermal control contact of Q is turned on, causing ]C to be triggered to work.
The audio signal output by the ◎ pin of LC is amplified by VT, and drives Y to sound an alarm.