Water boiling electricity called circuit design

Industrial Router Crystal 3.2*2.5mm 3225 26M (26.000MHZ) 12PF 10PPM 20PPM 30PPM

inductance

SMD aluminum electrolytic capacitor

The electric caller is used for water boiling to inform the owner that the water has been boiled, so as to avoid empty burning or even burning.
The electric circuit includes three parts: a temperature sensing head, an RS trigger and an acoustic reporting circuit, as shown in the figure. The temperature sensing head is a small stainless steel tube (or copper tube) with a plug, and is equipped with a neon diode D1 for detecting the water temperature, and D1 is connected in series in the voltage dividing branch in the circuit. At room temperature, due to its high reverse resistance, it is broken, making 555
The 6 and 2 feet are high and the 555 is in the reset state.
The 555 is used as an RS flip-flop, that is, a flip-flop is made by using the difference between its set terminal and the reset terminal potential. As the water temperature in the kettle increases, the D1 reverse resistance in the sensor head inserted in the water gradually decreases; when the water is boiling, the resistance of the RP1 is adjusted so that the Dl reverse resistance value and the RP1 partial pressure are 1∕. 3VDD, after a few seconds of water on, the voltage divider value will be lower than 1∕3VDD, that is, the low level of the 555 pin 2 is set, the 555 is turned OFF, and the 3 pin turns high. It provides the working voltage for IC2.
IC2 uses the music integrated circuit HY-2, which has 3 pieces of music. HY-2 adopts level and timing trigger mode. Each time it is triggered, a piece of music is broadcasted in sequence, and each song plays for about 30 seconds. The typical working voltage of the chip is 3V. In order to ensure its normal use, the voltage regulator R2 and DW are used in the circuit, and the voltage is regulated by 2CW51 and the voltage is +3V. In the figure, the trigger terminal is connected with VDD, that is, when the water is boiling and the IC1 output is turned to a high level, IC2 is energized and triggered, HY-2 will immediately release the music of the memory, and the well is amplified by VT, and the speaker is driven to report. sound. After the owner hears the call, or lifts the kettle, or unplugs the sensor temperature, the signal stops; if the owner does not take timely measures, HY-2 will play the 3 pieces of memory repeatedly until the owner comes.