In this project, we'll be electrifying our ukulele!

The outcome of this modification to the ukulele will allow us to plug in the instrument directly to an amplifier or a plethora of effects and processing pedals. We'll also be adding a control unit into the ukulele to let the player adjust the tone and volume on the side of the instrument.

Step 1: Watch the Video!

Click here to watch on YouTube

Check out this quick video to see the electric ukulele working and hear how it sounds! It also guides you through the steps below from start to end.

Step 2: What We'll Need

We're going to need:

A piezo transducer
A 47 nF capacitor
A 1/4 inch mono audio jack
A paper protoboard
2 200k ohm variable resistors
Polymer clay

I didn't have any potentiometers small enough to use as knobs for my soprano ukulele, so I'll making some with variable resistors and polymer clay instead.

Where to buy

Piezo transducer: http://amzn.to/2dHoVZA
Electrolytic Caps Pack: http://amzn.to/2d6upKs
1/4" Mono panel jack: http://amzn.to/2dPR3Ws
Perfboard: http://amzn.to/2cQcN7q
Variable resistors: http://amzn.to/2dPOB2i
Polymer clay: http://amzn.to/2dYNUGP

Soldering gear:

Weller WES51 Analog Soldering Station: http://amzn.to/2dq7Q4m
MG Chemicals Silver Solder: http://amzn.to/2dHj0nq
Helping hand: http://amzn.to/2dc553O

Testing gear:

Multimeter: http://amzn.to/2dc54N6
Breadboard & Jumpers: http://amzn.to/2dHknm2

Step 3: Find a Piezo

Here's a piezo from an old microwave.

You can find one of these in pretty much any appliance that makes a beeping sound.

We're going to only need the piezo element, so carefully remove the plastic housing if it has one.

Step 4: Make a Small Potentiometer

Here's the variable resistor that I'll be using to make our potentiometers with.

I cut a piece of credit card to fit the cavity.

Then I glued it down in place with a dab of Krazy glue and cut it down to a half centimeter in length.

Step 5: Make a Tool to Cut Knobs

To make the clay knobs, we'll have to make a tool to cut out polymer clay,

I took the tube from a pen and wrapped around it a piece of aluminium that I cut from a soda can.

Hold the aluminum piece in place with an elastic and slide it out about 2 centimeters.

Step 6: Cut Knobs

Now we roll out some polymer clay to about a centimeter in thickness.

Put our variable resistor into the clay as far as the knob needs to go.

Then slowly push and twist the cutting tool into the clay around the resistor.

When we reach the bottom, undo the elastic to release the clay.

Now we can carefully remove the resistor.

After we cut out two knobs, we'll set it on a plate and bake it in the oven at 250F for 30 minutes.

Step 7: Test Knobs

Once it's done baking, we can fit it back onto our resistors and give it a test with a multimeter.

Step 8: Place Knobs Onto Protoboard

To hold the knobs, we'll take a paper protoboard and cut it to height of our ukulele.

Glue the resistors in place with a bit of hot glue and make sure they're level with each other.

Use a dab of Krazy glue to attach the knobs to the resistors.

Step 9: Drill Holes

I sliced open a tennis ball and used it to hold the ukulele in place.

First make a small hole with a nail and hammer.

Then make a bigger pilot hole with a small drill bit.

Then, using a stepper drill bit, make a 1/4" hole.

After that I took some blue acrylic paint and painted in the holes.

In total there's three holes drilled - there's two holes on the side for the knobs, and one in the back for the output jack.

Step 10: Wire the Components

The schematics to this project is fairly straight forward.

We'll first wire up the piezo to the mono jack. We want to control the amount of signal going into the jack, so we'll add our volume knob here to create a voltage divider configuration.

Adding a 47nF capacitor in parallel will change the tone of our signal by cutting off the high frequencies. To make this adjustable, we'll wire the capacitor through the tone knob so we can adjust the amount of current going into the capacitor.

To prevent a mess of individual wires, I chose to use a ribbon cable like a piece from an old IDE cable.

Solder in all the connections as per the diagram above.

Step 11: Put Components In

Once we're done wiring, we'll need to fit everything into the ukulele.

We'll put a chopstick through the hole of the output jack, and tape the audio jack onto it. This is so that we can easily guide the jack through the hole.

First thing we'll glue is our piezo. Apply a thin layer of epoxy glue onto the smooth side of the piezo. Then reach in and attach the piezo as close as you can to the bridge.

After the piezo is set, we'll pull our output jack out from the back and glue that in place with hot glue. We'll then add a washer to secure the jack in place.

And lastly, we'll feed the knobs through the side holes and hold it in place with some sticky tack. If you have a small glue gun, you could just hot glue it in place through the sound hole, but I don't, so I'm just using epoxy glue here to set it in place.