[sdiy] Simplest random source

[harrybissell]

Try the "Control Oscillator / Noise Source" from the PAiA 2720
synth... with small resistors it would lay out pretty tight... three transistors
and only one supply voltage...

OTOH... the amplitude of the noise falls sharply at low frequencies... so
it might not be all you want. You'll need at least a +15V supply.

If you need to do a 5V solution... the shift register method is best.

H^) harry

Seb Francis wrote:

> I'm not convinced sofware is the way to go.  It would be no problem to do it in software, but I have a couple of reasons for wanting to use analog:
>
> - CPU cycles are a premium - this PIC is doing a *lot* and I don't want to waste more than 10 cycles or so getting a random number.
>
> - I have a hunch that a simple random algorithm (such as what could be achieved in 10 cycles) would sound a whole lot different (not so nice) to the human brain than for example taking a sample via A->D of some white noise.
>
> I've seen really simple noise generating circuits using just a diode or transistor plus a couple of opamps .. I guess I was hoping there might be a way to get analog noise using just a couple of transistors or something - the quality of the sound doesn't really matter, as long as it's random.
>
> Seb
>
> Paul Perry wrote:
>
> > At 12:11 AM 16/11/02 +0000, Seb Francis wrote:
> >
> > >So what I'm looking for is the absolute simplest (minimum components - PCB
> > space is scarce) way to make a 0->5V random source.  The PIC A/D has a 120pF
> > hold cap, so I don't think a very HF source which averages to the same
> > voltage is suitable.
> > >
> > Why yes..... the simplest solution, is ANOTHER PIC!
> > I'm sure the code is out there..
> >
> > paul perry (not a programmer)
>
> "J.D. McEachin" wrote:
>
> > On Sat, 16 Nov 2002, Seb Francis wrote:
> >
> > > I've just finished routing the PCB for my MIDI2CV and I've realised
> > > I've left off a vital part .. I need a random source for the digital
> > > random LFOs.
> >
> > > So what I'm looking for is the absolute simplest (minimum components -
> > >
> > > Any suggestions?
> >
> > Software.  Use your brain and you should be able to generate a completely
> > random number.   Look around the web if you have problems coming up w/ a
> > suitable algorithm.
> >
> > JDM