Frequently Asked Questions

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Basic Questions on the Open.Theremin

Q: What is an Arduino and where to get it?

A: Arduino is a widely used single-board micro-controller to make using electronics in multidisciplinary projects more accessible. The hardware consists of an open-source hardware board designed around an 8-bit Atmel AVR micro-controller. Many projects and product are based on the Arduino witch makes the board a well documented and easy to use standard in open source electronics. Genuino is a different brand name used in Europe for Arduino and Genuino UNO can be used as well. You can buy Arduinos/Genuinos in online stores all over the world. See here for a list of stores:

Q: What type of Arduino should I get for the Open.Theremin shield?

A: The Open.Theremin is a shield for the Arduino.UNO, the most popular Arduino. Genuino is a different brand name used in Europe for Arduino and Genuino UNO can be used as well. The older Arduino Duemilanove should work as well. For the following Arduinos the software is not compatible (they do fit mechanicaly though): Arduino Leonardo. Arduino Mega.

Q: What kind of antennas can I use?

A: As the Open.Theremin is quite flexible and can be easily tuned electrically you can use almost any electrically conductive material as an antenna. The boards are optimized and tested for aluminium rods, 6 mm diameter and 50 cm long. Thicker, thinner and slightly longer and shorter antennas should work well also.

Q: What if I want to increase the distance between the antennas.

A: You can just put a piece of wire from the antenna pad on the circuit to the antenna is self. The wire should not be too long (<50 cm) as it adds to the length of the antenna. Best is to use stiff wire to prevent the wire from moving around in your case and thus changing the signal.

Q: How can I reprogram the wave lookup table?
A: If you open the open.theremin software with the arduino programming environment (IDE) you should find one tab named "theremin_sintable.c" that contains the values for the wave form. There are 1024 values that define the wave, each can take values between 0 and 2048. Just change the numbers and upload the software to the theremin.

Q: is MIDI possible with the Open.Theremin?

A: Yes, this is possible. Thanks to Vincent Dhamelincourt who developed a MIDI implementation for the Open.Theremin V3. For code and instructions see here.

Questions on ordering kits.

Q: Do you sell kits?

A: Yes, I do sell assembled and tested Open.Theremin V3 shields. I produce in small batches. Please check the Small Batch Store for availability. The design is open source so you can also make modifications and improvements or even build the boards your self. I do not sell Open.Theremin.UP / RC / LC anymore and I do not sell plain circuit boards or parts.

Q: I don't have a paypal account, and I am not interested in having one, that's why I wanted to ask if a bank transaction also would be possible?

A: If you click on the "Buy Now" button in the store you will be redirected to the pay-pay website. There you can choose to pay with a debit or credit card without a pay-pal account. Would this work for you?

Q:Will there be extra duties or taxes for my country

We ship worldwide. Specific duties and taxes for you country may apply and are to your responsibility.

Q: How long will shipping take to my place

Shipping time varies a lot and is dependent on the country, the season and the custom checks. All theremins are shipped within 1 week by Swiss Priority mail. Please expect 1-2 weeks extra for the shipping. We had theremins that arrived in Japan in 4 days. German custom seems to be rather rigorous and may delay the shipment up to one week.

Q: Is there a tracking number for my shipment

There is no tracking number with the free shipping orders. If you prefer registered shipping with tracking number, this costs extra 6 Euro. Please contact us before placing your order.

More technical questions & trouble shooting

Q: What kind of coils can be used?

A: The coil for the resonator circuit can basically be any 1000uH coil that fits. I noticed that some coils have a bigger temperature drift than others. Coils embedded in plastic seem to be more stable. From Reichelt L-PISG 1,0M might fit. To reduce temperature drift you could try to isolate the coil with some hot glue or similar.

Q: The volume antenna does not seem to work

Make sure the theremin is grounded well. This can  be a reason for the volume antenna not working well. See the instructions for different grounding methods.

Q: Is my soldering ok?

Check your soldering. All pins need to be soldered properly. Make sure you have not shorted any pins. Also make sure that you plug in the shield to the Arduino correctly. All boards were tested and working properly before shipping.
For a good introduction to soldering and on how a good solder joint should look see "soldering is easy" by Mitch Altman.
Use this "Soldering Joint Quality Chart" I made to see if your soldering is ok. The first two is what you are aiming for.

Q: The pitch or volume antenna does not seem to be calibrated properly?

You can check the calibration data using the built in "Calibration Diagnostics" - here is how to do it.

Notes to be clear

Open source hardware pioneer Limor Fried uses to said "being obscure is the enemy" of OSHW projects and I am aware of this. This is why I decided to put up the following list to write down things that I have in mind and that I will hopefully document more in detail as time comes. Anyway if you feel something is missing or if you are stuck with a problem, please just ask.


Q: The blue LED does not turn on
A: To use the extra functionalities provided with the Extension Kit you need to install the expanded software "Volume and Wave Switch for Extension V 2.0".

Q: Do I have to perform the calibration routine every time you power it up?
A: The manual calibration only needs to be done once when setting up the theremin with you antennas and housing. The automatic calibration is done automaticaly on startup or when you press the button and only takes a second.

Q: Can I increase or decrease the range (sensitivity) of the antennas
A: Yes, you can do this by setting a slightly higher or lower frequency (than 600Hz) during calibration. If you set it lower (say to 500 Hz) you get a bigger range. 700Hz will make a shorter range (easier to play).

Q: What is the function of the potentiometer P1 (100k)
A: The analogue potentiometer is an option and is not used by the current software and is not assembled on the boards sold. It can be added and programmed easily and be used for calibration for example. Maybe you want to experiment with it and see if it can be useful. The potentiometer voltage goes to analogue pin 5 of the arduino. Instead of an analogue potentiometer a digital incremental encoder could be used as well.

- The first extension kits came with two extra threaded plugs. Unfortunately the weight of the whole kit was too high and I had to remove those to avoid shipping problems. 

- The files for Version 1.2 can be found here: SchematicV1_2, BomV1_2, AnleitungV1_2, BoardLayoutV1_2, SchemaLayoutV1_2

- The files for Version 1.1 can be found here: Layout File - OpenThereminUNOV4.brd  / Layout File - OpenThereminUNOV4.sch / OpenThereminUNO_BOM.pdf

- I did not test the control voltage output on V1.1 a lot. When I finally tried to make it work I found that there is an interference problem (two pists two close). I fixed this in new version 1.2 by connecting to a different PWM pin. Version 1.1 can be easily corrected by rewiring (will document if required)

- At low volume level the Open.Theremin.UNO used to be quite noisy. This was due to imprecise measurement of the volume antenna. I corrected this and uploaded a new software version V1.2. The software should be compatible with V1.1 board, so just upload the new software to the Arduino.

Open.Theremin.UP / LC / RC:

- The quarz oscillator built with the 4060 on the is also used to clock the microcontroller on the open.theremin.UP print. So if the 4060 oscillator is not working correctly or if the LC print is not connected to the UP print the micro-controller will not work and you will not be able to program it.

- The HEF4060B oscillator is actually over-clocked with 16MHz. The HEF4060B from NXP does it anyway, but I noticed, that chips of other manufacturers may not. Further more, the clock is generated at 15V and then divided to 5V for the micro-controller by the resistors R12/R14. This is simple but not so nice (better suggestions welcome). If your clock is not clean, you may try to adjust the resistors.

- On the newest Open.Theremin.LC design I added pads for a dedicated quartz (X2, C26, C27) only for the micro-controller. This option is not used yet. The software needs to be adapted. Just leave these pads open.

- The different "options" with the potentiometer to adjust the LC circuit are not documented yet. I only use option 1 with the variable C.

- The CV outputs are not programmed in the current software version. It's actually just one or two lines (to set the PWM Out), I did not use it so far.

- On earlier schematics there was a ATTiny 261 controller. The software got bigger and now a ATTiny 461 is used.

- The theremin needs two voltages (5V for the micro-controller and 15V for the theremin circuitry). The two LM317 generate these voltages from the input voltage (18V). The voltage drop from 18V to 5V is high and the LM317 gets quite hot. You can measure the voltages on the indicated test pads.

- All capacities are ceramic or electrolytic. No tantals (even if indicated differently and not corrected yet).

- To program the micro-controller you need a programmer. I use the programmer form ATMEL (AVRISP mkII In-System Programmer). There are cheaper alternatives available on the net.

- Version 1.2 is the newest version of Open.Theremin.UP. Old files (V1_1) are available here: Schematic V1_1, PartList V1_1

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