[sdiy] Really Low, LFO

[Veronica Merryfield]

What about a counter and a ROM with a R/2R converter. Use a few address lines for wave select and the others to count it out. The nicety of running this slow is that the R/2R can be made to work very well for a large number of bits. A larger ROM and cascaded counters would give a significant division ratio from a clock. A possible gotcha wold be glitches at each change but these can be filtered with a simple RC filter set to well below the bit change frequency and above your highest output frequency.

Veronica

On 2010-04-02, at 2:49 PM, Tim Parkhurst wrote:

> On Fri, Apr 2, 2010 at 1:51 PM, Kyle Stephens <lightburnx at yahoo.com> wrote:
>> Can anyone point me to some reading material on infrasonic oscillator design? I want to build a really low, low LFO, with a period of around half an hour (yes, _that_ slow!).
>> 
> 
> Hey Kyle,
> 
> How about dividing a square wave waaaaaay down? You can use a variety
> of oscillator designs, of course, and you could use an integrator
> (with a big honking cap) to smooth the square out. Alternately, you
> could possibly use an R/2R converter and sum several divided down
> squares (higher freq's get attenuated more) to get a pretty fair
> approximation of a slow triangle wave (still might require a smoothing
> cap).
> 
> 
> Tim (or a pretty fair approximation thereof) Servo
> -- 
> "Sire, the church of God is an anvil that has worn out many hammers."
> - H.L. Hastings
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