Miniature Loop Alarm


Posted on Feb 2, 2013

A few months ago, I decided to build a compact, yet effective alarm. My demands were:- simple construction, reliable operation, very small power consumption, and, most of all, small size. I started with CMOS logic gates, but was soon forced to abandon the concept after a few unsuccessful (and far too complicated) attempts. Then I suddenly realized that a simple transistor switch might do the job and I was right. As you can clearly see from the schematics, the circuit is utterly primitive and consists of two identical transistor switches. Each has its own alarm LED and they`re coupled to a neat 82dB buzzer. The two 1N4148 diodes are used to prevent a signal from one sensor from triggering both LEDs.


Miniature Loop Alarm
Click here to download the full size of the above Circuit.

The sensors used are either wire loops or normally closed reed switches or even a combination of both. You could, for example, tie a wire loop to your suitcase and place a reed switch to the door of your hotel room. Since this little alarm is intended




Leave Comment

characters left:

New Circuits

.

 


Popular Circuits

VLF Radio Receiver circuit
Bar-code-scanner
Oscillator DesignGuide Reference
Some Voltage Regulator Ciruits for Microcontroller based Projects
Pic microcontroller project
Auxiliary Lighting Circuit
AR-300 DC arc welding machine circuit
XTR115 116 Basic circuit diagram connection
And broadening the delay circuit



Top