Open water notification Circuit Design

Posted on Mar 28, 2007

Boil water on the kitchen gas stove, once the water is boiling, if not stalled, spilling boiling water will come out, the flame extinguished. Gas spills, very safe. Water can s

Open water notification Circuit Design
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olve this problem after opening notification device. Circuit works : The circuit uses a thermistor as the temperature sensing element, when the water temperature rises, the thermistor resistance decreases, A point potential increases, when the A point potential is higher than the IC-1 inverters convert voltage, IC-1 will output low, IC-2 output high. So that IC-3, IC-4 audio oscillator work composed, piezoelectric ceramics sound. When IC-2 output low, IC-3, IC-4 consisting of audio oscillator is not working, piezoelectric ceramics silent. IC selects C066 two-input NAND gate four, working voltage 3V ~ 18V, the power supply circuit is 3V ~ 6V; RT thermistor resistance is about selected 1k ; piezoelectric ceramics selected diameter of 27mm; use an ordinary resistor 1/8 or 1/4W metal film resistors. Production and Testing Method : find two waste fluorescent starter shell, made with iron clamps, snapping the top two starters and secured with screws. Wherein a starter can be set in the mouth of the kettle to get water temperature. Thermistor two pins welded on the other starter cover and filled shell, attention must be close to the thermistor within the shell wall, it is easy to heat. Welding on the outer lead thermistor temperature sensors on the well. After all the components check and correct weld can turn on debugging, the temperature sensor set in the kettle mouth, adjusting RP and other water boils, the piezoelectric ceramic sheet just sound, several times repeated testing, it can officially use. To change the sound frequency can vary the capacity C2. If you feel that the sound is not enough, you can add transistors in the output of IC-4, amplification sound effects.

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