A simple voltage supply for digital circuits
Monday, February 20th, 2006I have a really nice course in Electronics at the moment and we are doing all sorts of things, but since it’s just an introduction to some physicists and not electrical engineering as such it runs a bit fast and jumps a lot of places, well enough about that 
So we have finally arrived at Digital circuits after two weeks of analog stuff. All the analog stuff is nice naturally but apart from sound it’s not really something you find in your everyday anymore (at last not if your everyday looks like mine, nerdish that is 
anyway my teacher proposed that if we liked we could continue our lessons at home (building a simple 3-bit decoder) it would be easy since a standard USB connection features a 5V DC supply which is exactly what is used in all digital connections (figures why it is used in USB devices so we could just use our computers as source! now this might sound trivial but it got me started on the idea of a simple home electronics setup, and I found that I wasn’t the first at that…
So first of all I build a simple little box for power:
Very simple design, some terminals, a switch and a junk plastic box I would guess
the total price to be around $4 It a very simple idea so you don’t really need a diagram
right? but I did the drawing anyway:
And Woila! a neat little supply for your digital dreams 
Anyway you should remember that there is a max current at 500mA on a SUB port so don’t
use it for heavy equipment…
Well so far so good… but what else do you have in the electronics lab? well two
other devices that we frequently have used is the Oscilloscope and Function generator,
but essential in analog design and they might come in handy here as well… so I thought,
well I’m out of luck the Picoscopes we use at Uni is around $300 each and I would
guess the same for our function generators… then I thought about it… what device
in a computer is used for both?… the sound card! now the naysayers will point out
that it only works in the audible spectrum and true it might be so for older cards,
but since high-freq formats is popular at the moment audible or not I found that my
sound cards ADC is rated at kHz divide that by two and we have a spectrum up to kHz
it’s not microwaves… but hey it for free! the real problem is with DC and low frequencies
that is below 20Hz… Anyway I searched for an application that would fit my need
and it seems that this company has specialized in this! they have some further guidelines
on there website.
And for the function generator? well every synth will do, but if you want it simple
and powerful the same company delivers one as well (and a spectrum analyzer for that
matter) so for around $10 (+ $50 for the program) your a fitted with some simple but
very powerful tools just right out of the little box under your table 
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Microsoft
Cisco