Multi-way pocket alarm circuit

Posted on Mar 28, 2007

This is a two-way can set the alarm circuit which uses a Schmitt IC, with responsive and sound and light show, small size, low power consumption, all of the elements is only 13, a very low cost. This circuit is divided into two parts by the A, B and R4,

Multi-way pocket alarm circuit
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C1 composition limit alarm. And in C, D and R5, C2 constitute the lower limit alarm function, the circuit shown in Figure 1.Usually RP1, RP2 are provided two upper and lower alarm point, the A and C inputs are high, the outputs are low leaving the oscillator are halted. When the temperature is too high, the thermistor resistance R1 decreases, the output high A, B start-up, the piezoelectric ceramic YD a high-pitched beep. At the same time, the light emitting diode LED1 lights on to indicate overheating. When the temperature is too low, the thermistor R2 resistance increases output high of C, D start-up, the piezoelectric sheet issued YD bass tone beep. Light emitting diode LED2 display temperature is too low.Since CMOS circuit static power consumption is extremely small, only microampere current level, so static power consumption mainly in the RP1, RP2 and thermistors. If we can use resistance at more than a hundred k special temperature resistance, RP1, RP2 a corresponding increase in the scale drawing press, the static power consumption can be controlled very small, it is extremely beneficial to prolong battery life.Component list as follows: Number Name Type Quantity R1,2 thermistor 1K 2 R3 resistance 3K 1 R4,5 resistance 2M 2 RP1,2 adjustable resistor 10K linear 2 Polyester capacitors C1 300P 1 Polyester capacitors C2 1000P 1 LED1,2 emitting diode µ3mm 1 Schmidt integrated circuit or IC CD4093 MC14093 1 YD piezoelectric buzzer µ20mm HTD20A-1 type 1 E battery lighter dedicated 12V small battery 1 The alarm uses the components is not large, do like so small matchbox.If instead of using photosensitive resistance thermistor can be used as the light intensity alarm. It can also be the other input of the Schmitt trigger use down as light, temperature bifunctional two-way alarm. It leads to a control signal from the LED fill light, humidification (ultrasonic humidifier) to compose automatically fill light and humidity controller.

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