Knowing resistors required


I've just started Arduino and am trying to combine the Keyboard and Photoresistor Theremin projects to make a keyboard with a light-sensitive pitch bender. I'm fine with the code, but I'm unsure of what resistors will be needed though and how to arrange the circuit.

Any pointers or tips would be appreciated!

Keyboard project: 07 Starter Kit: Keyboard Instrument - YouTube
Theremin project: 06 Starter Kit: Light Theremin - YouTube

links to those projects would be useful for context...

It's just project 6 and 7 from the Starter Kit book - edited my question with links to the Arduino instructional vids

so how would you see this working?

I'd like to implement the keyboard in much the same way as the book (resistor ladder) and then additionally, I'd like to use the phototransistor to be able to bend the pitch of whatever note is being played at any one time. I would likely have it so depriving the phototransistor of light will bend the note downwards by up to a whole tone and a regular unimpeded light source will play the note without any pitch bending.

does not seem too complicated

  • implement the resistor ladder and read which button is pressed on A0
  • implement the photoresistor but read the value on pin A1

upon button press, select a frequency from the array as they do, but do some maths to modify the frequency based on A1's value before passing it to tone()


The code/logic isn't an issue for me, it's just knowing how to adapt the circuit.

Just to check - I can literally add the phototransistor implementation on to the end of the board after the keyboard implementation? Should there be any integration between the two? I'm new to circuits, so if something seems too obvious to point out, please say it anyway.


the phototransistor is just a separate circuit, just connect it to A1 instead of A0

the Arduino's 5V pin is capable to deliver enough current for the resistor ladder and the phototransistor to work at the same time.

5V --> buttons / resistors ladder --> GND. ➜ plus connexion in the right place to A0
5V --> Anode -- Cathode --- resistor ---- GND ➜ plus connexion in the right place to A1

Ah ok, cool - thanks!

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