Hi everyone. I am building a Theremin circuit. It is working with hand gestures. One of it is oscilloscope and other is amplifier circuit. It takes data with camera. Then DAC turn the signals to analog signals. Left hand will control amplifier circuit and I have problem about it. I will control volume with amplifier circuit. I am not sure how should i design Amplifier circuit? I mean does digital pot works and cut off frequency for oscillation circuit is important for the amplifier circuit too?
I'd start with a simple opamp buffer and a pot meter on the signal input. If you bias the audio/AC to e.g. 2.5VDC you can use any rail-to-rail 5V-rated opamp; I often use AD8605. The pot meter can be a digital one as you suggest.
For the power stage just use any audio amplifier module; something like a simple class D thingy.
Any amplifier you design needs to work with the frequencies you feed into it. When it comes to audio, the high frequency end is generally not a problem since it only needs to go to 20kHz or so. At the low end you need to realize that any coupling capacitors tend to make R/C filters with bias resistors and the input impedance of the next stage. Calculate the cut-off frequency of this (virtual) filter and adjust the capacitor value accordingly.
So far so good, but the next bit is odd:-
Do you mean oscillator and not oscilloscope?
Now this is the leap I don't understand. How do you convert the image from a camera into a reading?
How do you turn this reading into an ADC value?
How much have you got working so far?
As to the amplifier you need what is called a voltage controlled amplifier.
I do not understand what you are trying to say here.
Maybe a block diagram would help us help you.
Mike, I think the idea is to use machine vision to track both hands and then use a DAC to output the desired waveform. So it's quite different from the Theremin as we know it from about a century ago.
Of course, this wouldn't require an oscillator as such, so there's still an inconsistency there.
I'd like to know that, too.
Yes but that requires a much more hefty device than an Arduino can deliver, unless you use a smart camera like the Husky Lens. Even then you might have trouble detecting right and left hands the right way round.
I agree, and that's also why I think your question for a block diagram is so relevant. It'll clarify these matters and hopefully the controller block will be more specific than "Arduino". The more powerful Arduino's like the Giga would qualify - the classic ones like the Nano...well, we both know how that will turn out.
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