Instructables
Picture of Infrared Intruder Alert
Stop intruders from trespassing on your property with this infrared alarm system.

Step 1: What You Need

Picture of What You Need
IntruderAlert_003.bmp
1. Garage Door Sensors like these
2. Wireless Doorbell Chime for $6
3. Photocell
4. Various components as shown in the schematic.
5. 5 Volt AC Adapter. You need a regulated supply so the voltage does not 'float'. A 1.0 Amp supply will typically be regulated.

Step 2: Prepare the Receiving Sensor

Picture of Prepare the Receiving Sensor
I tried to get inside the garage door sensor to access the circuit but after a bit of prying decided that it would be better to leave it intact and keep the waterproof design as it was clear the case was glued together. So, using a photocell over the receiver LED was the best option.

1. Epoxy the photocell to the receiver to prevent any light from getting to the cell. I also added some coats of spray paint as these cells are extremely sensitive to light.

NOTE: To see which is the receiver, you can power up the sensors by using 3-4 "AA" batteries (4.5-6 volts). Connecting a 100ohm resistor connected to one of the sensor positive (+) lines will tell you which is the receiver when they both light up.

Step 3: Build the Circuit

Picture of Build the Circuit
The circuit is designed so the photocell triggers the 6 volt relay which in turn closes the switch on the transmitter, sending the signal to the receiver and ringing the chime. I built it as small as possible because I wanted everything to fit inside the smallest Radio Shack hobby box.

Step 4: Finish it

Picture of Finish it
Install the new circuit along with the transmitter circuit inside the hobby box. I drilled 3 small holes. Two on the side for the wiring that goes to the sensor transmitter/receiver and power and one more hole on the bottom that the leads for the photocell would fit inside. I also used rubber grommets and silicone to seal those holes. I used "5-Minute" epoxy to glue the box to the bracket that came with the garage door sensors.
 
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austech1 year ago
Replace the chime with several Li- Po batteries with a timed switch and a capacitor, put it at the entrance to your house, and when they arrive... Flaming doorway, what burgalar wouldn't think twice?
sunofgod1 year ago
"Epoxy the photocell to the receiver to prevent any light from getting to the cell"
This statement is confusing to me and a few others, surely this will block the receiver?, but after reading the preceding sentence
"So, using a photocell over the receiver LED was the best option"
I am no longer confused, If I may make a suggestion you could reword the statement.

"Epoxy the photocell to the receiver LED, to detect the LED turning, on and prevent any light from getting to the photocell"
Is it possible to hook this up to a phone? So it calls you about an intruder while you are away?
tomtortoise3 years ago
does anyone know of a substitute for the transistor i cant find them at radio shack or online?
In a circuit such as this the transistor is not super critical. Use a PN2222 or even a 2N2222 and it will be fine.
Amazing!!!!
Aron3132 years ago
Nice!!!!!! :O
eneergcam5 years ago
now you know when the crazy man down the street has gone crazy and is planning to kill you with an axe!
I thought it is spelled ax not axe. Axe is a brand of hair products
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It's spelled both ways.
what if he goes around it though?
you would have to know it's there. or you could just jump over it
Yeaaahhh, i didnt think about that....know i only have one arm :(
oh no! you better duct tape it back on! lol

maybe you could surround your house by building a few of these
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M-16 with armor piercing ammo.
Why AP? And why an M-16? You just need a long shelled silenced .17, Leave the neighbours wondering
exactly!
Or 1 gross tonne of C-4.
30 gigaton payloaded warheads
Lolz, that's the same power I use to open cans.
dont say lolz
*Lolz*
lolz hehe im board
Hire Chuck Norris to round house kick them.
 zero creativity here... you guys need to watch more SAW
I suggest you have a pit in the ground filled with punji sticks and tigers
And ninjas.
but ninjas don't need a pit for people to fall into they. work alone
True, but they'd want to keep the Tigers happy by petting their heads.
Now were thinking
This is in the suburbs, most likely not to do but while in the woods thats a different story >:()
Vulcan minigun.
wtf you dont have to have a massive gun to kill someone... did it ever occur to you, you could just use a knife?
Exacto blade catapult.
KNIFE!
check out the Ghurka Khukri knife. One of those in a good size would make the holder feel pretty safe
I *love* those.
Exacto knife blade catapult.
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