Shock alarm circuit

admin April 7, 2010 20 Comments
 Description. Here is a simple shock sensitive alarm circuit that has many many applications fro home to automobiles.The main application of this circuit is to use it as an anti theft alarm in automobiles.A peizo electric sensor is used as the shock sensor which has to mounted on the door which you have to protect. Here the IC1  LM 3558 is wired as an inverting Schmitt Trigger.The POT R1 sets the threshold voltage of the circuit.R1 is used as...
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Door handle alarm

admin May 15, 2008 4 Comments
 Description. The automatic door handle alarm circuit gives a audible alarm and glows a LED when somebody touches the handle of the door.The circuit is latching type and continues to produce sound until it is switched off. The transistor Q1 is wired as an astable multivibrator whose output is used to bias transistor Q2 to conduction.As a result the transistor q3 and LED are in OFF state.When someone touches the handle ,the capacitance of the human body damps the...
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Fire alarm circuit

admin January 21, 2014 127 Comments
Description. Here is a simple fire alarm circuit based on a Light Dependent Resistor (LDR) and lamp pair for sensing the fire. The alarm works by sensing the smoke produced during fire. The circuit produces an audible alarm when the fire breaks out with smoke. When there is no smoke the light from the bulb will be directly falling on the LDR. The LDR resistance will be low and so the voltage across it (below 0.6V). The transistor will...
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Infrared Motion Detector Circuit

admin August 3, 2016 255 Comments
In this tutorial, we have explained how to build a DIY (Do It Yourself) Infrared Motion Detector Circuit using 555 Timer IC, IR Diode, 2 comparator IC’s and other associated components. An Infrared Motion Detector circuit can be designed in different ways using different sort of components. This one is a low cost, easy to build one designed using inexpensive and easily available components. Note:- If you are looking for reviews of a commercial Motion Sensor/Detector to install at...
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Burglar Alarm Circuit and Projects

admin November 9, 2018 2 Comments
In this article, we list different burglar alarm circuit and projects we have designed and published in CircuitsToday. A burglar alarm is basically an intruder alert system used to prevent theft/robbery and protect one’s premises. Burglar alarms or alert systems can be designed in different ways; from very simple sound alarm system to the advanced and feature rich system which will send SMS alerts, activate sound alarm, turn ON lights, turn ON CCTV cameras, close the main gate etc....
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Light sensing intruder alarm

Sensitive Intruder Alarm Circuit

admin November 2, 2018 67 Comments
Super light Sensitive Intruder Alarm Circuit Intruder alarms are popular devices used in high-security areas as well as civilian houses to detect and alarm the presence of any intruders. There are different kinds of intruder detection alarms, some detect movements by using a laser, some use pressure variations etc.  Our intruder alarm works using an LDR (light dependent resistor). Also known as photoresistor its resistance varies with the intensity of light falling on it. Its resistance decreases with increase...
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Metal detector circuit

Metal Detector Circuit

jacky July 25, 2018 42 Comments
Metal Detector Circuit I always wanted to make a metal detector seeing how cool it was in all Hollywood, Bollywood movies. One thing I realised is; things aren’t as difficult as you think it is. After all, I found that a metal detector is really simple and easy to make. So in this post, I am sharing with you “How to make a metal detector” Description This is the circuit diagram of a low cost metal detector using a...
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