The gist of it is to fit a fun music module from those musical greeting cards inside a keyboard and wire it to the caps-lock key to trigger the music each time the key is pressed. Do it on a friend's keyboard, unbeknownst to them, and wait for them to press caps-lock by mistake. Genius!
I'm in the ideal situation because many of my colleagues have the same standard issue Dell keyboard at work, so I took one home, wired the caps-lock key with some cheesy Christmas music and took it back to work ready to put my colleagues in the mood before the holidays. Once one is bored of it, I could simply move the keyboard to someone else!
Here's how to make yours!
- Keyboard with caps-lock LED
- Musical greeting card
- NPN transistor
- Thin wire
- Phillips screwdriver
- Solder iron & solder
- Electrical tape
Step 1: Choose the right keyboard and take it apart
Here we have a USB Dell keyboard with the caps-lock LED next to the wire connection.
Turn it over, remove the many screws holding it in place and keep them in a safe place for now.
Take the cover off and keep it close by.
The caps-lock LED is likely to be marked as such on the circuit board. It will be easy to locate.
Step 2: Get the musical module
Take the module out carefully and look at how the music is triggered.
Here it's a piece of paper preventing the contact from the battery. Classy.
Step 3: Find a space for the module inside the keyboard
Step 4: Wire the module to the keyboard
Fire up the solder iron.
Cut two lengths of wire (about 15 inch each, preferably one red and one black), strip and tin them.
Cut the musical module switch away, you will replace it with the transistor.
Get the NPN transistor and hold it flat side up, pins away from you. Spread the pins apart.
- Solder the left pin to the positive contact of the battery.
- Solder the right pin to the other contact of the switch, leading to the music chip (big black blob).
- Solder the red wire to the middle pin.
- Solder the black wire to the same contact as the right pin of the transistor.
- Solder the other side of the red wire to the positive side of the LED.
- Solder the other side of the black wire to the negative side of the LED.
Step 5: Test it and clean up
Now you need to test it. Make sure the board on the keyboard is in place properly, plug in the USB cable into your computer, test the keys to make sure it works ok, and... press caps-lock. Can you hear the music?
Yes? Victory! Tidy-up the wires with electrical tape, make sure you can close the keyboard properly and put it all back together. Congratulations, you're done!
No? Here are a few things to check that could have gone wrong:
- The solder connections could be dry, weak or otherwise dodgy. Check them carefully.
- The transistor could be the wrong one or the wrong way around, or soldered at the wrong location on the music module.
You can use a screw-driver to short the left and right pins of the transistor (not the middle), you should hear the music. If not the problem might be with the music module itself.
You can unsolder the wires from the LED side and touch them to a 1.5V battery (red one to the positive), you should hear the music. If not, then the transistor is probably at fault (is it really an NPN?)
Step 6: The final product
Step 7: How does it work ?
Here's the schematics.
I've highlighted the new connections and transistor in red.
The transistor replaces the switch on the musical module. A transistor is essentially an on/off switch that turns on when it receives current on the B pin. When you press the caps-lock key, the keyboard tries to light up the LED, which sends a current to the transistor and triggers it like a switch and turns on the music! When caps-lock is pressed again, the keyboard turns off the LED, which stops the current to the transistor, which opens the circuit again and stops the music.
Thanks Kipkay for the original idea.
Check out my blog for my other projects.
Thanks for reading!