The post explains an LED based intruder position indicator circuit which will indicate the position of the burglar throughout the secured corridor as the person tries to sneak past the area.The idea was requested by Mr. Michael.

Requesting a Intruder Position Indicator Security Circuit

Your articles are nice, well done. sir can this, close and open door security circuit be mounted on an iron door?.sir can you help me with a security circuit that will have five to ten(5-10)light emitting diode indicating the position of an intruder in a house.the circuit will work in such a way that when the intruder is at your gate,the LED will light up and when he or she enters your compound,the second one will light on.Thank you sir in Advance.

The Design

The requested idea can be actually implemented through a few very basic circuits as described below:

Using an LED/LDR laser beam interruption method.

Using an proximity sensor circuit

Using piezo electric device sensor

Using a PIR based circuit.

Here we will pick the most simple one out of the four options, and utilize the piezo sensor concept for implementing the position intruder indicator circuit and detecting an intruder who may crossing the prohibited section of the premise.

As shown in the figure below, the proposed intruder position indicator security circuit can be built by positioning many such modules across all those areas which need to be monitored.

How it Works

The circuit basically consists of a monostable multibrator circuit using the IC 555, which is activated when T1 is activated through the attached piezo buzzer element.

We have already learned from one of our previous post regarding how a piezo could be used for generating electricity, here the same concept is enforced for triggering the transistor in response to a physical strike or vibration on the piezo.

For implementing the intruder position indication, one such unit could be positioned across each of  the selected strategic locations, with the piezo element hidden inside a carpet or a door mat.

Whenever an intruder attempts to cross the secured zone, the person steps on the carpet or the door mat where the piezo is installed, and in the process triggers the circuit into action, illuminating the LED.

The circuit module could be installed somewhere near to the piezo, and the LED terminated and fitted at the location where the LED indication is required to be visualized.

The values of R3, R4, and C2 determine for how long the LED remains switched ON and then switched OFF once the piezo is triggered, and these could be appropriately adjusted for acquiring any desired length of illumination period.

Parts list

R1, R4, R5 = 100K
R2, R6 = 1K
R3 = 1M pot
C1 at T1 base  = 0.22uF
C1 at T1 collector = 4.7uF/25V
C2 = 100uF/25V
C3 = 10nF

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