Building a Guitar Tuner with a 555 Timer IC to Generate 440Hz Tone

I always expected some adjustment would be required which brings me back to my original question.

Right now I've got the circuit tuned to the open B string on my guitar (verified the B string tuning and 555 circuit tuning with a tuning fork app on my ipod) . I'll see if I can't check the resistance and instead of using the 100K pot use a single resistor. I might get lucky and have that particular value in my collection, but it will probably require more than one resistor in series.

Most of the resistors I have are gold band (5%) and I can swap various resistors in my collection and get as close to the sweet spot as possible. So, my question is might it be productive to use theCSS555C and program the internal trim capacitor of the CSS555C to compensate for the 5% errors in value of the resistors (let's say for argument purposes that "close to the sweet spot" is a single 68K resistor with a 5% variance)?

Recall that this was my blog post that prompted this discussion: http://www.science20.com/square_root_not/blog...licon_solutions_programmable_555_timer-108814

Here's the corrected circuit from my previous post:

Cool! I did not know about this part -- all of the things you wish the 555 could do, bundled into one little chip!!

So, here's my 2¢:

* consider if you want to be tweaking each one before it goes out the door
* BUT, if using the plain ol' 555, then, really, even 1% resistors and 1% capacitor will not be enough to get a consistent enough frequency -- would have to use a trim pot and tweak each one.

"Cool! I did not know about this part — all of the things you wish the 555 could do, bundled into one little chip!!"

I know! The css55c is the neatest thing since sliced cheese...ok, I might be exaggeraitng a bit, but it is a pretty cool little chip.

"consider if you want to be tweaking each one before it goes out the door"

This circuit was never meant to go into manufacturing production--it's just a simple circuit for hobbyists.