Hardware Hacking Projects for Geeks

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Chapter 9, How to Build a Cubicle Intrusion Detection System

11. Align the system

If you are using the Radio Shack entry alert product, set it up in the door-

way of the cube you want “protected.” The kit includes a red reflector and

instructions on setup.

If you are setting up the laser-based version, mount the main project

enclosure so that the laser will fire across the opening of the cube or office

you want protected. Mount it with tie wraps, metal coat hangers, or even

Velcro. Power it on and look to see where the laser places its dot. Take a

small mirror and secure it with double-sided foam tape or other adhesive so

that it reflects the dot back at the main enclosure. Use the laser pivot mount

to point the laser so that it hits the photo-detector assembly. When properly

aligned, the LED on the board will switch off. It will switch on when the

beam is interrupted. Multiple mirrors may be used to cover a larger area.

The LED laser should be able to project a beam over 50 feet.

Finally, attach the “warning” LED cable assembly to the circuit board and

check that it switches on when someone breaks the beam. Place it so that it

is inside your field of vision when you are working.

Project Demo

After you have aligned the laser or entry alert box and set the warning LED

on your desk so that you can see it, call a few fellow office workers and ask

them to step in to your cubicle. Before they arrive, put on a set of head-

phones and play some of your favorite music. When your colleague enters

your cube area, you will see the warning LED switch on. You’ll never be

surprised again!

Extensions

A number of additional features can be easily added to the system. The laser

box currently requires a separate 12V DC power supply. You may want to

add a four-conductor RJ-11 connector and pass the power on two of the

wires.

If you would like your PC to be able to interface to the cube intrusion sys-

tem, you will need to add a serial output to the controller via an RS232 level

converter such as the MAX233. This chip can be added to any free I/O port

on the BasicStamp2. Every time an entry event happens, a byte of data can

be sent out and recorded by the PC. You will need to add some code to the

BasicStamp2 to enable this feature; I leave this as an exercise for you.

Extensions

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Part II: Advanced Hacks, Tools, and Techniques

The output transistor, Q1, can trigger other devices such as web cams to

grab a series of images each time the sensor is triggered. The Axis web cam

(http://www.axis.com/) has an input connector that allows external devices

to trigger an image capture. This camera can be easily connected to the

cubicle intrusion system.

The Q1 output transistor could also be used to trigger a motorized toy or

electric water gun to provide a surprise for the unsuspecting intruder. The

best way to do this is to replace Q1 with a larger transistor (the TIP112 from

Fairchild Semiconductor available, from DigiKey, will work well).

Extensions

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