[sdiy] First DIY synth (555 osc.'s)

[Brockr0 at cs.com]

  perpetual writes:

>  so i was playing with a 555 oscillator last week.  more info here:
>  www.geocities.com/aurelialuz/shadow.htm
>  
>  what i've found is that all this talk about instability is true.  this
>  thing is really temperature sensitive.  and we're not talking like a
>  couple cents over an hour, i'm talking like octave flucuations from
>  minute to minute.  this thing is powered off a battery too, so i've got
>  both demons of instability working against me.  if i was really
>  interested in creating some sort of stable oscillator, i'd look
>  elsewhere.

The 555 makes an acceptable oscillator.

Timing error astable configuration: ( National CMOS LM555C)
    Drift with temp  150 ppm/C
    Accuracy over temp  3 %
    Drift with supply  0.3 %/V
  
Not great, but acceptable. Octave swings over minutes cannot be caused 
by external components either. Worst case would be a ceramic timing cap 
but you would have to heat it up and cool it down dramatically (100 C) to 
experience what you describe. I would suggest that you have a defective 
component or an error in your circuit that is causing this instability.

IMO - if you are trying to make an analog oscillator that operates from
batteries and does not use a voltage regulator or reference, (I don't know 
why you would), I suspect you cannot do better than a 555 for stability.

Brock