[sdiy] inexpensive chips for oscillators (still learning...)

[Bob K]

Wow.  Thanks again for the more information.

I'm a beginner but can read schematics and am learning my way around a
breadboard.

The initial project is just going to be a little noise box with two
pots, one to control the frequency and the other to control the
volume, and no inputs.  After I get that going I'll add more
oscillators and more knobs.

So it looks like I'll start off with the CMOS 7555/TLC555 and see what happens.

I'll take a look at the PAiA schematics and see what they're doing.

Again, thanks!

-Bob

On Mon, Sep 26, 2011 at 11:26 AM, Scott Gravenhorst <music.maker at gte.net> wrote:
> Dave Kendall <davekendall at ntlworld.com> wrote:
>>You probably know this already, but if using 555s, go for CMOS versions
>>(7555, TLC555 etc) which draw *far* less power. It's my understanding
>>that the regular 555 can cause problems with power consumption when
>>switching.
>
> The datasheet I have for the 7555 has current graphs that show the difference between
> the bipolar 555 and the CMOS 7555 while they are switching.  The difference is
> amazingly large.
>
> In fact, the PAiA Fatman had been designed using bipolar 555 timers for the two VCOs.
>  Unmodified, it has a notable problem of soft synching the VCOs when they are close
> in pitch.  This is because even though the 555 is fed power through a 100 ohm
> resistor with a 100 uF cap to -12V, there is still a significant current spike at
> switching time that propogates to the other VCO.  A fix was designed by PAiA which
> replaces the 100 ohm resistor with an LED.  Another fix that I found after learning
> about the 7555 was to simply replace the bipolar 555 with CMOS 7555.  The two fixes
> work about as well as each other, but I prefer the 7555 fix over the LED fix.
>
> +1 for 7555.
>
> And you can go to www.paia.com and look at the schematic for how they turned a 555
> (or 7555) timer into a VCO.  It is a _linear_ VCO, but enterprising lovers of expo
> could probably convert the VCO's voltage to current converter to use expo instead of
> linear pitch CV.
>
>>On Sep 26, 2011, at 17:21, Bob K wrote:
>>
>>> Hi everyone,
>>>
>>> New here.  Hi.  How's everybody?  Fine?  That's good.
>>>
>>> After skimming through the two Forrest Mimms books I have and "Make:
>>> Electronics", both books are making a point that 555 and 556 chips are
>>> a good (and cheap) start for breadboarding oscillators.
>>>
>>> I'm planning on a bulk purchase (bulk meaning around 10) of the above
>>> mentioned chips and was wondering if there are any other cheap chips
>>> along the lines of the 555 and 556 that can be used for oscillators?
>>> I'm going to search online for advice as well but thought I'd run this
>>> question by everybody here.
>>>
>>> Thanks.
>>>
>>> -Bob
>>> _______________________________________________
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>>>
>>
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>
> -- ScottG
> ________________________________________________________________________
> -- Scott Gravenhorst
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