[sdiy] pseudo random LFO

[>>>marjan<<<]

Mitchell Hudson wrote:
> 
>     So after that discussion of pseudo random voltages a while back I
> got the idea to make one of my own. I liked the idea of mixing several
> LFO's together. So am I starting with a simple LFO from Tom G's site
> (thanks Tom for providing a most excellent web site). I changed it
> slightly by taking out the switch between the triangle and square
> outputs and using them both. It looks like I can do this?

Yes, but you'll need one more set of such LFO's to make it near
random/chaotic, as here you'll have control over waveshape,
but mix of just two frequencies, not enough for the effect you need.

> I also want to
> use this with a 15v power supply. Which I am not so sure about. Could
> any one give me a tip, can this circuit with 15v or do I need to chang
> something?

Nope, it should work OK. Maybe adjust 2k2 res to have sq same level as
tri wave.
You can add cap with switch to 0.1u to have different ranges (like 1nF
for
audio range, o.1u normal, 1uF for very low range), same effect could
be done with adjusting 390K res. 
With some voltage divider (trimmer) and few diodes to gnd you can make
sine
from tri. If you mix them use large input res like 1M otherwise you'll
need
buffer for tri to work right. Sine will have low amplitude so make that
input
reistor lower to get more amplification or make it's own amplifier.
Ceramic cap 10-100nF across the rails wouldn't hurt.
Make that 470 res a bit lower (100 or 220 ohms) to get slightly higher
freq range.

>      The last thing I want to do is mix all of the outputs into one, I
> haven't drawn this into the diagram yet. I am thinking to use the mixer
> from the Forest Mimms book on op amps.

Use standard inverting summer.

cheers,


marjan