Aren't you annoyed when people come in your room without permission. In this instructable you will learn how to stop people from entering in your room. The steps will tell you how can do it in different ways.

Step 1 and 2- How to detect the people that are trying to get into your room.
Step 3, 4 and 5-How to stop people from entering your room.
Step 6 and 7- Help for step 5

Step 1: Tripwire Alarm

The first way to detect the people is a simple tripwire alarm. It is very cheap, requires very few items and is very easy to make. The things that you will need to make the tripwire alarm are

9v battery and clip
Piezo or any siren or any kind of buzzer
A plastic peg/clip
Some thick thread and a piece of plastic

This is someone else's idea and is also available as another instructable

Its just a simple circuit and instead of the switch we'll use the clip. On both the points of the clip we'll use some duct tape or foil paper to attach the wire. Now if we leave the clip it will conduct if if we press it from the other side it will stop the circuit. We will simply take a peice of plastic or any other non conductive thing and tie a thick thread to it. Now tie the other end to some where on the other side and put the plastic peice in the clip to stop the circuit. When the person comes, the thick thread will get pulled and the plastic will get removed and thus, the piezo siren will start up.The schematic and a photo of the alarm made is given in this step.

Step 2: Invisible Laser Alarm System

The second way to detect people is an invisible laser protection alarm. It won't work like the expensive ones but it will still be invisible and the person will not be able to see the alarm. It is based upon a LDR (light dependent resistor) and IR(infrared) LED. The things that you will need to make this alarm are

2 coin cell batteries (CR 2032/2025)
Transistor 2n3904/2n2222/bc547
1k resistor
LDR (light dependent resistor)
Piezo or any other siren or buzzer
Strong IR LED

It is a very simple circuit. It is to be put on the gate. You will need to make two different circuits. Each at one side of the gate. One circuit is for sending the invisible light and the other is for receiving the light. Its just a simple IR LED which emits a light which humans cannot see and on the other side is a dark detecting circuit. When the person comes from the gate he will stop the light from being received and the alarm will sound up. The schematic for the dark detecting circuit and the installing scheme is given in this step.

Step 3: SHOCK Protection System

The third step will show you how to stop people from entering in your room. It will shock them a little so that they don't try to enter in your room. Just look at the first pic. It explains the device well. When anybody touches a negative and positive rod he gets a mild shock which is enough to convince him to not to try again. The things that you will need to make this device are

Some metal rods (or the substitute I've given below)
A high voltage low ampere circuit
A battery for the circuit

The metal rods can be very expensive for you because this device needs many of them. So as a substitute you can make a cheaper one instead which is given in the next step.

Step 4: Substitute Metal Rods

The substitute metal rods are very easy to make. To make them you will need

Some newspaper
Some foil paper
A little tape

First to make the base you should roll one large sheet of newspaper from the corner and keep rolling it as tightly as you can and once rolled seal it with some tape. Once the stick is made(as shown in the picture) just roll some foil paper on it and it should be ready.

Step 5: Dark Room Plan

This step shows the best way to keep people out of your room. Now I would like to ask who likes to come in a whole dark room. NO ONE. So just turn off the lights of your room and no one will come, and if someone does, he won't be able to see anything. BUT then how will you see????? Well there is a simple answer to that you will just need to place some IR LEDs in your room. Place as many as you can at the corners and sides of your room and turn off the lights. But still there is one more problem. Humans cannot see the infrared light. To see it you will need some special equipments about which you will learn ahead. As long as the peson coming in your room does not have them he will see the room as dark but you will see the room as lit up.

Step 6: Seeing Infrared Light-1

The first way to see the infrared light is using a camera. Cameras can see the infrared waves. Just switch off the lights and turn on the IR LEDs. See the room with a camera. The room will look very bright, but the people who are not using a camera will see the room as very dark.

Step 7:

Sometimes you can't have a camera with you at all times. So instead you can make a non-electric infrared seeing gadget. To make it you will need 3d goggles. One won't do so you will need 2 of them. Just take one of the 3d goggles and carefully take out the blue and red plastic pieces. Now stick them to the other 3d goggle in a order so in each eye you have 1 red and 1 blue plastic piece. You should be seeing purple color from each eye. Well just wear these goggles and you should be able to see the infrared light.

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