Theremin Toy using Arduino

I wanted to make a little toy for my granddaughter to play with when she visits. I know like most kids, she enjoys things that make sounds and have different colored lights on them and if she does something, the toy does something. I thought about a Theremin and decided to add a RGB light that changes color in a similar way that the sound does. This gave “birth” to “Oh”.

I call it “Oh” because when I look at it, it sort of reminds me of a face saying the letter “O”. Try it yourself. Look in a mirror and say “Oh”. There you have it.

Nothing earth shattering here. I “borrowed” some code that was already out there for the Theremin and for playing with RGB LEDs, tweaked them a bit and put it all altogether in one of my little cases.

Here’s a video of it in action.

Theremin Toy using Arduino

Step 1: Parts

Ultrasonic Module HC-SR04@ $2.50 on eBay

Anarduino An Arduino Compatible 24 DIP model kit @$5.40 on eBay

BreadBoard P.S. Breadboard Power Supply @$1.50 on eBay

Mini Speaker Item G19651 at Electronic Goldmine @$1.25

Module Wiring Dupont Wire Connector Cables 20cm (female-female) @$1.50 on eBay

RGB LED Common Anode 5MM LED 50 for $4.00 on eBay LED Holder

5MM LED holder 50 for $1.39 on eBay

2.1mm DC Pwr Jack @ 50 Cents

#2 hardware I use 3/8 inch bolts to mount speaker on case. Check out

1K Ohm Resistor 1/8W or 1/4W to control current to RGB LED

Molex Header Item G18974 at Electronic Goldmine @$2.00 / 10

Heat Shrink Tubing @$5.00 for an assortment of sizes and colors on eBay

Case enclosure MB-132 at @$3.00

Arduino UNO Used to program ATMEGA328P chip


Step 2: Wiring it up and putting it together

Theremin Toy using Arduino circuit

First, grab the code from the next step and program the ATMEGA328P chip in your UNO and then set that aside.

Next, we will work on the Anarduino.

The first picture above shows the wiring of the Anarduino after it is made and the Molex pins are added. See my Kitchen Sink Clock Instructable for more info on putting the Anarduino kit together.

To fix up the Bread Board P.S. for use in this project please see the video in my Instructable about that.

Some special wiring is done in this project to make a “Y” cable to tie the Trig and Echo pins together on the Ultrasonic Sensor into one “signal” line. You can see what I mean by looking at the long orange lead on the right hand side of the second picture. I have a piece of orange heat shrink tubing covering the exposed solder connection.

There is one other special wiring and that is a bit harder to see. The purple wire going into the RGB LED connects to a 1K ohm resistor and the other end is soldered to the anode lead of the LED. I have that covered with purple heat shrink and, if you zoom in on that section of the photo, you might be able to see the “bump” in the line which is the resistor.

Other than those two things everything is pretty straight forward.

Plug the programmed ATMEGA328P chip into the Anaduino socket and you are all set to put it all together.

Looking at the second picture, you can see how I laid out everything and then secured things down with double sided foam tape.

At this point it is a simple thing to plug in all the connectors to the right pins on the Anarduino and the power supply module as per the wiring diagram above in the first picture.

Please test it out before you screw down the cover to make sure you have all your connections right.


For more detail: Theremin Toy using Arduino

About The Author

Ibrar Ayyub

I am an experienced technical writer holding a Master's degree in computer science from BZU Multan, Pakistan University. With a background spanning various industries, particularly in home automation and engineering, I have honed my skills in crafting clear and concise content. Proficient in leveraging infographics and diagrams, I strive to simplify complex concepts for readers. My strength lies in thorough research and presenting information in a structured and logical format.

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