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A simple mini alarm circuit

2015-01-08 10:12  
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This article describes a simple mini alarm circuit. The circuit is very simple, very helpful. If you understand this principle is not very thorough, it is recommended to understand some of the important components of the circuit: BC547, 1N4148 . This is a selection of small independent alarm circuits. They have a very low standby current; suitable for battery operation. Sw1 is painted in any one or a magnetic reed switch contacts; But as long as it does work you can use any type of switch you like. Using multiple switches if it fits your application. The output device is a "piezoelectric" buzzer, requires a current of about 10 horse. Provides a voltage buzzer is appropriate, the circuit will work from 5-15 volts. Its main feature is to describe each of the alarm circuit diagram itself. Each of the circuit will be printed on an A4. 4093 years Cmos Schmitt trigger version Cmos 4011. For the present purposes these two are interchangeable. However, in 4093 there is an improved switching performance, is the most obvious time, if time is greatly extended. Any exact length of time will depend on the characteristics of the components actually used; particularly accurate tolerances capacitor and the switching point Cmos door. 11 & 12 of the circuit, the value of the treatment as a rough guide R6 & R7. The door switch 3 and the characteristic points to determine the actual thermistor temperature range available. Change the value of R6 will allow you to access different areas of the temperature scale; while changing the value of R7 will allow you to change the width adjustment is available. Although they are described as alarm circuit, they will have other applications. May be replaced by the sound of a buzzer or a small relay opto-isolator, the timing components may produce the desired change in output performance. Any relay coil should have a resistance of at least 270 ohms; but for battery operation, the higher the better. If you use an optical isolator, connect a 1 k resistor in series together. 

 

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