DSO nano and synth circuit

A few days ago, a co-worker let me borrow his DSO nano to run a few tests. First thing I decided to do was throw a really chaotic waveform at it. I built this little synth with 2 square wave oscillators.


Square wave oscillator schematic

It is kind of comical to call this a synth or even a set of oscillators. It is basically a simple NOT gate arranged in a feedback loop. The capacitor fills up until it reaches the breakdown voltage of the internal diode in the NOT gate, at that point, the signal is inverted to GND and the capacitor discharges. When it reaches ground, the output signal inverts again and the process starts over. The result is a square wave. The potentiometer controls the amount of current flowing into the capacitor and thus alters the amount of time it takes to fill up. In effect, altering the frequency of the square wave. I built two of these and muxed the signals together with some resistors, kind of like a fixed mixer. The overall signal is pretty hectic, with weird beat frequencies and strange tiny oscillations in the individual frequencies themselves.

I found it pretty hard to get the DSO nano to get a good read on it but it was pretty hard with my regular scope as well. Probably not the best waveform to start with. So, I decided to try out some simpler waveforms. I programmed an Arduino to just spit out ‘a’ on the UART every second and used a rising slope trigger to freeze the waveform. It worked really well for that. It also worked really well for just a square wave generated on the Arduino. It was able to guess the frequency with accuracy. Unfortunately my phone had died at that point and I couldn’t get any pictures or video.

Overall I found it pretty simple to use and a surprising amount of functionality for it’s small size and price. I have to admit though, I wouldn’t find much use for it as I am almost always in front of a desk where I can use my USB scope and software. I think this would be more helpful for someone who works in ‘the field’ so to speak. It is pretty much as good as you are going to get in a pocket-sized package.

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One Comment

  1. peno
    Posted March 4, 2010 at 7:31 am | Permalink

    you never cease to amaze me

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