Usually signal generators are expensive devices which are found only in laboratories. In this page an (almost) no-cost method is presented use the on board sound card as a signal generator, to accompany the expEYES kit. This will augument the capabilities of the kit. This will be certainly useful for some demonstration regarding waves and their interactions.
For this we are using a small Java program called Original Synth (released under GPL V. 2.0) and can be downloaded from here.
The programme can generate following types of waveforms:
These standard waveforms can also be 'edited' to make some
Once you download the program, unzip and open the file named
originalsynth2-0-2.jar with any of JRE (Java Runtime
Environments) on your system.
When the program opens, it looks like this, and many options are
Go to the Tab menu and click on New. Select an identifier and
give it a name. Then this window appears, with options becoming
In the Generate menu you can choose from the given waveforms.
We have chosen the triangular waveform here.
For each of the waves, we can control its duration and
frequency. Even though there is an option for amplitude, it only
changes amplitude virutally (on screen), and not in the actual
signal which is generated. The output is safe for expEYES between
\(\pm 1\) V. Also another thing to note is that changing the
frequency, does not change the waveform on the screen. But this
can be readily heard immediately on the speakers. One more
parameter which is important is the duration, this determines
time for which the wave will be ON. And finally there is a Play/
Stop button which does what it says. You can have multiple wave
forms in different tabs and switch to them as required. This is
all about the software that is required, now let us turn to the
hardware part, of which actually there is only little.
We need to use the standard 3.2 mm audio jack (stereo or mono ) for
taking the signal to the expEYES kit. This is the only
investment needed, hence almost no-cost. With the audio jack in
to the headphones port in the computer, the audio is routed to
the headphone instead of the main speakers. We connect the signal
wires from the audio jack to any input and ground to GND. With
this setup we are able to see the waveform generated by the
program on expEYES.
In the picture below case we have set the frequency for a
triangular wave in OriginalSynth at 4,000 Hz. in expEYES we see
the waveform and the fitted frequency is 4008.9 Hz.
And below is a sine wave generated at 50 Hz, which is received as 50 Hz.
We present below a table comparing the values of frequency from
the programme and the values calculated by the expEYES kit for a
OriginalSynth (Hz)expEYES (Hz)
We can see that above 10 kHz, the results are not very stable. And
in general amplitude reduces with increase in frequency from about
0.9 volt peak to peak to 0.69 volts for 20 kHz. But for lower frequencies ( ~ 5 kHz) the stability is pretty good.
Now something about the editing part of the generator. In OriginalSynth, we can edit the basic waveforms. And then the generated wave has that form. For example if we edit the basic sine wave as below
Then we get a sine-wave just like this in the expEYES
* @source: http://orgmode.org/mathjax/M...
Feb. 18, 2015, 11:23 a.m.
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