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ChelseaBack

September 16, 2013 14:44

Making a Light Theremin Instrument

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An adaptation of the Arduino Starter Kit light theremin project.

In this project I decided to adapt a project from the Arduino Starter Kit, and chose to make a light theremin but with a few additions of my own.

Instead of using the Arduino UNO board I used a minimal Shrimp and added a few extra components:

  • an LED power indicator

  • a jack socket output

  • a potentiometer for volume control

What is the minimal Shrimp? This is basically like a very simple Arduino, is cheap to build and good as a starting point for projects.

A bigger LDR than used in the Arduino starter kit was selected because it fitted in with the look of the project better.

Shopping list

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For this project I had to order most of the parts in, and first I had to decide what type of enclosure I wanted to use, dial, switch, jack socket, LED and LDR.

My intentions for the end result were to use this as an instrument and to make it look like a hand held effect pedal.

Once all the parts were ordered I then just had to wait for them to arrive!

Programming the ATmega bootloader

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Since I was using a new ATMEGA328-PU chip this had to programmed with the Arduino bootloader, which was done using an ISP shield with an Arduino UNO board.

Prototyping

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Next I prototyped the minimal Shrimp circuit on a breadboard to make sure that it worked.

After putting all the components into the breadboard there were some issues with programming it, and I found this to be because the transmit and receive connections were connected the wrong way round to the USB UART.

After getting past this initial glitch I then added the light theremin components to the breadboard to prove that this circuit would work.

Planning the layout

Before I could build the minimal shrimp onto the perfboard I had to plan it out on a perfboard template, by doing this I had some instructions to follow when building my circuit.

Assembling

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I had a slight problem when all the components were soldered onto the perfboard: when this was connected to a computer to be programmed, I found that I was unable to do this.

I thought this was the transmit and receive connections between the USB UART and the ATMEGA328-PU being swapped. It turns out this wasn't the case and it was because a capacitor was shorting out due to the legs being crossed with a resistor. I repositioned the resistor so that it was no longer shorting out the capacitor, and re-swapped the connections so they were in there original positions.

I then added a 5v regulator into the circuit to so that it could run off a 9v battery.

Enclosure

The next step was to measure the diameter of the holes for each component I intended to fit into the enclosure. I had to mark out on the enclosure where the holes were going to be before drilling.

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I then began to fit the components directly onto the enclosure.

I had to make a few adjustments when fitting the components, because I had placed the LED over the jack socket and the LED bezel was too long and so this had to be shortened in length, which then resulted in it not fitting properly in the hole so it had to be secured with glue.

The potentiometer also had to be sawed down to the correct length.

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I then proceeded to fit the perfboard into the lid of the enclosure on nylon spacers. This created a little bit of difficulty with the height of some of the components, but after a few minor adjustments this was soon solved.

Completion

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With all the soldering completed it was time to fasten the lid on the enclosure and test.

When first testing I found that it was making a strange sound and not the one I expected it to make! So I re-opened the enclosure and checked the insides to be sure nothing was shorting. Everything appeared to be fine except for I had accidentally connected one end of the LDR to ground instead of 5v. After this was fixed the light theremin worked fine.

Putting it to use

When I set out to build the light theremin I had it in mind to be used as an instrument, and when it was completed my boyfriend borrowed the theremin to be used in some of his band's recordings.

I don't think he had great expectations of the theremin due to the lack of a tuning control. However, when plugged into a 40w amplifier to both of our surprises it sounded great!

Conclusion

I found making my own light theremin from scratch a little tricky in parts, and this was the first real project I had undertaken which wasn't part of a kit, so it required a lot of planning and research. Overall the project was enjoyable, as it is both functional and individual!

if you're interested in building this project you can find it on DesignShare.

ChelseaBack

Trainee Electronics Engineer for AB Open. Love to try new things and build interesting projects!