Connect the musical element from a singing greeting card to the caps lock LED on the victims keyboard. Now each time they press the caps lock key the music plays (and quite loud too).

This is a great sleeping prank -- It might be found on the first day, or several weeks from the implementation. It's the perfect prank.

Difficulty: Easy, but involved. (ability to solder and use a multi-meter helps)

Disclaimer
If you decide to do this prank, understand that it could be a career-limiting move if it is done on your boss and/or somebody without a sense of humor. I would also recommend experimenting with a dummy keyboard that you don't mind destroying first.

Why Caps?
True, most people don't use caps lock very often, if ever, but unfortunately not many other keys are linked to an LED. Also most keys are only pressed momentarily, which would require a more complicated circuit to work effectively. The num lock LED turns on and off several times during boot time, so that's out which only leaves the caps lock as a viable solution.

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Origin of this Project
This was originally posted on on my blog (before KipKays video):
http://blog.mozmonkey.com/2006/april_fools_hack/

Step 1: Setup

To start you’ll need, of course, several musical greeting cards. Hallmark stores usually have a section dedicated to these cards. You’ll also need these tools and supplies:

1. Screw drivers (Phillips and a wide slotted)
2. Needle nose pliers
3. Soldering iron + solder
4. Thin wire (22 gauge works well)
5. NPN transistor
6. Electrical tape

You can get all these from your local RadioShack.

I bought a CoolHeat soldering iron for this project due to its great portability. If you get one of these be sure to purchase at least 2 replacement tips since they’re brittle and WILL break during normal use.

Step 2: Getting the Music.

The first thing you want to do is remove the musical element from the greeting card and cut off the excess paper around it. Be careful not to cut the wires!

Step 3: Switch Work - the Transistor

We now need to replace the metal switch with your transistor. You don't need to know anything about transistors for this project, just make sure you purchased an NPN type transistor and follow along.

Metal Switch Parts
The element already has a switch, that we'll be modifying for our purposes. The bendable metal part of the switch I’m calling the metal tab (or switch arm), and thing it connects to, or touches, I’m calling the contact area. You can remove the paper or plastic thing that the card used to make contact when the card is opened.

Transistor Work
Take the transistor and bend the center pin back slightly. Then slide the transistor onto the musical element switch area with the outer pins on top and the center pin on the bottom .

Now make sure that one of the outer pins is resting on top of the metal tab and the other outer pin on the contact area. (see the picture with notes)

Lastly, using your needle nose pliers bend the metal switch tab back over the transistor pin and make sure it holds it tightly. Now solder the other other pin to the switch contact area. (see second picture with notes)

Step 4: Lets Wire It Up!

Cut two lengths of wire about 12 - 15 inches long. Solder one to the switch contact area (see black wire in picture) and other to the center pin of the transistor. (see both pictures)

At this point you’ll want to use some electrical tape to secure the center the transistor pin and protect it from being pulled on by the wire. Just tape it down to the paper and make sure it's secure.

Step 5: Deconstructing the Keyboard

Using your phillips screwdriver remove all the screws from the bottom of your keyboard. This is where a small electric keyboard is useful.

Important: On some keyboards there are screws hiding under the rubber feed.

After all the screws are out, use the slotted screwdriver to separate the keyboard halves. Be very careful with this step since it’s likely to create visible damage.

Step 6: LED Setup

Find the caps lock LED and locate the positive and negative pins on the circuit board. You can do this by either using the diode checker on your handy multi-meter or by using a small battery and a couple wires to to light it up.

Fish the wires from the musical element up through the keyboard and to the LED.

Solder the wire from the center transistor pin to the positive LED pin and the other wire to the negative pin. (the image is from an ergo keyboard)

If the LED is not attached to the circuit board (as in the image) you can solder the wires straight to it. Be quick to prevent overheating the LED. However, most keyboards have the LEDs attached to a circuit board. In that case solder the wires to the same point on the bottom of the board where the LED is soldered to.

Step 7: Finishing Up

Most keyboards don't have room inside for the musical element. Just fish the wires out through the same place the main keyboard cord goes in, close it up and tape the musical element to the bottom.

You’re done, plug it in and try it out!

Step 8: Results

Late one night I went into the office and carefully chose 3 keyboards to terrorize and an hour later I was done. The following day the first person got the music playing right away, since he always uses caps instead of shift. He was baffled for a couple of hours, muting the sound on his computer and still wondering why it was making noise. Eventually he turned over the keyboard to find my note, and got a good laugh out of it. Strangely enough, he didn’t want me to remove it.

The second victim found it sometime after lunch. I wandered by, acting as innocent as I could, and suggesting “Try turning your sound off” then asking “Did you install anything today? Could it be a virus?” She started getting a bit concerned and I couldn’t hold a straight face any longer and ended up giving away my guilt.

The last guy never uses caps, so after waiting 2 weeks for it to happen and I had to coerce him to press the key.

I still have 5 more units setup and ready to go, I just have to find more victims…

Video
Somebody took my instructions and made a video out of it. Here it is:
http://www.metacafe.com/watch/327832/great_keyboard_practical_joke_prank/

Step 9: Reversing the Prank

There are 3 easy ways to reverse the prank:

1) Cut the wires to the musical element. Be sure to tape them off so they don't touch and short the keyboard out. (30 seconds)

2) Take your handy electric screwdriver and Cool Heat soldering iron and open the keyboard back up and unsolder the wires. (10 minutes)

3) Open the keyboard back up and cut the wires right at the circuit board. (5 Minutes)

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