Boss Alarm
AGlass0fMilk 
Introduction
It's a common occurrence in any office -- you're on Facebook or browsing SparkFun when all of a sudden your boss walks in to see that you're not working.
This project aims to avoid that embarrassment and frowns from management. The Boss Alarm alerts you of anyone walking into your office and automatically changes the active program on your computer. The sensors are inconspicuously hidden in cute woodland creatures that are guaranteed to brighten up your office and definitely not creep out any of your coworkers!
The Boss Alarm uses an infrared breakbeam sensor made with a few common components. The design is based on schematics from this article with a few modifications.
There are three components to the Boss Alarm. There is a transmitter (hidden in the squirrel) that sends an invisible beam to the owl. The owl contains an infrared receiver (namely, the TSOP38238 IR Receiver Diode) and also another infrared transmitter. The last component is another IR receiver connected to a Teensy 3.2.
The Teensy is configured as a USB keyboard device. When the beam between the owl and the squirrel is broken, the owl sends a signal to the Teensy. When the Teensy receives this signal, it simply sends the Alt+Tab keyboard command to your computer to change the active program. If you are on a different operating system, you can change the key commands to whatever you want (for example, Windows Key + D to minimize all programs). You can trigger practically anything using this project.
Check out a video of the project in action below:
Materials
You're going to need a few things to build this project yourself.
Along with those parts, you will need a few other parts and tools:
- Various common parts including resistors, capacitors, and transistors (this project uses an NPN 2N3904)
- A single LED, but just get a whole bunch 'cause they're awesome!
- Hookup wire
- Wire strippers and pliers
- Soldering iron and solder
- It's always a good idea to have desoldering wick in case you make mistakes (it's easy to forget the pinout of those IR receivers...)
- You may need a common electric drill and bit set
- Heat-shrink tubing and a source of heat
If you plan on installing the electronics in the woodland creature enclosures, you will also need access to a 3D printer and a hot glue gun. You may also wish to paint them.
I highly recommend obtaining some sort of oscilloscope for troubleshooting, but it is not necessary to complete this project. You may also want to acquire a decent multimeter for diagnosing any issues you encounter.
Recommended Reading
You may need to read up on a few subjects to wrap your head around this project:
- Through Hole Soldering
- How to use an Oscilloscope
- Infrared Light for Electrical Engineers
- Infrared Communication
- Getting Started with the Teensy
- The 555 Timer
- How to Read a Schematic
- Transistors
- Pull-Up Resistors