ELECTRONIC LAPTOP CAJON

A cajón (Pronounced ka-hone) is a box-shaped percussion instrument, played by slapping the front or rear faces (generally thin plywood) with the hands, fingers, or palms. They are usually quite large and the player sits on them like a stool. Some have a wire snare that adds a rattle sound. I wanted to build a smaller, more compact version as a prototype, and for proof- of - concept. I will eventually build a wooden version but this one functions so well, I thought it deserved its own Instructable. 

If you like to slap out the beat on an empty beer case, this one will appeal to you as it is made of cardboard. I decided to add amplification because of its small size and was pleasantly surprised by the sounds it produces plugged into a standard guitar amplifier.

Hardware items: I used a medium sized, unused and unassembled pizza box, a pool noodle, some double-sided mounting squares, stick on furniture floor protector feet and a small piece of scrap wood.

Electronic items: Some fine hook- up wire, 2 DPDT ( Double pole double throw) switches, a 6 foot connector cord with 1/8” plugs, (the kind used to connect your phone to other audio devices), a 1/8” to 1/4” audio plug adaptor and 4 piezo transducers. These are available from any electronic supplier. I ordered mine online from: digikey.ca. 

These are Listed as -BUZZER ELEMENT- It’s the part that makes those beeping sounds from your coffee maker or microwave. For that, however, it requires an oscillator circuit. It works just as well as a mini speaker or microphone, and in this case functions like a guitar pickup to detect drumming sounds. 

Part#- 7BB-20-6L0

Price: $1.18 CDN -cheaper if you buy 10 or more

You will need solder and a soldering iron, a glue gun, drill and drill bits.

Note: The cord, adapter, mounting squares, furniture floor protectors, pool noodle are all from the Dollar Store.

Assemble the pizza box but don’t close it yet. Cut a 3” hole in the bottom. I used a hole saw but you can trace around a DVD and cut with an x-acto. Cut two pieces of the pool noodle to the height of the box and then cut them longitudinally in half. Hot glue them around the hole at 12, 3, 6, and 9 o’clock. These support the lid and mute the sound. Drill holes for the audio cord and switches in the back side of the box and install the switches. A small block of wood should be hot glued below the audio cord exit hole so the cord can rest on it and be fastened to it later.

Attach the mounting squares. I measured the half way point between front and back and also half way between the pool noodles and each side for the lid. For the base, I staggered them a bit to avoid oscillation between the piezo transducers. 

Next, I pressed the transducers onto the mounting squares and made all the connections. 

A wiring schematic is provided but it is imperative to connect the transducers in parallel, that is, red to red, and black to black. This is also true of the audio cord. Cut off one end and strip the insulation back a couple of inches. There will be 3 wires, red, white, and black. I checked with an ohmmeter and found that the black was the tip of the plug and the white and red, were the two sleeves. Remember this is a stereo plug and the guitar amp is monaural. Solder the white and red together and you’ll solve that problem and allow it to work with a standard guitar amp. Feed the cord through the hole drilled and hot glue it to the wood block leaving enough of the inner wires to reach one switch. ( Be careful to make your solder connections to the transducers quick to avoid overheating them.)

The audio cable connects to the centre position on both switches. The bottom transducers are connected in parallel to one side of one switch. The top transducers are connected in parallel to the opposite side of the other switch.

This will allow the output to be switched between top only, bottom only, or both at the same time to change the sound. Orient your switches so that it is easy to know what transducers are connected. On mine, both switches up= top, Both switches down= bottom, Left down / Right up= All

Before closing the box, attach the adapter to the plug end of the cord, plug into your amplifier and do a test. Making sure your switches are in the right position, tap each transducer in turn. You should hear a drumming sound. You might want to put some beads of hot glue on the wires to keep them from rattling against the box and producing stray sounds.

If it all works, carefully close the box and start drumming. Experiment with the settings. You’ll be surprised at the effects.

I installed 4 furniture feet on the bottom and a description of the switch positions. I also glued some wood veneer to the top and front to strengthen the lid as it will take a pounding (pun intended). The decals are just for decoration.