In addition to others' notes here;

PICs use less current by FAR than the original 555's which were sort of
power hogs;  Use a low-power CMOS version, and make sure you have that
version's datasheet if you use one, if you go the 555 route.  Also,
could drive a 555 at a higher frequency and divide it's frequency down
by a proportional amount.

Electrolytics have huge temperature coefficients, using one for timing a
555, you want something like a Mylar or other low-variance cap.  Those
gre REALLY pricey IIRC by the time you reach 100uF, so use smaller C,
larger R, and watch the construction, leakage on those pins 6 and 7 will
change your timing.

I'd lean towards a PIC chip as well, myself.  12C508A, OTP part for a
"forever unchanged" design, a /JW (windowed) part if you expect to ever
need to change the time period or software, (you could use a few stacked
(series) Shift Registers and jumpers/traces and cut/short jumpers for a
programmable time in the low uSec resolution range, too;  That'd be sort
of handy, come to think of it!  Hmmm, use BCD rotary switches if you can
find some surplus ones, hmmm... <G>)

With a PIC you could throw in a Duty Cycle adjustment if desired <G>
Also make various wave-forms, if you wanted...

Voltage ratings, are sort of a not-care really! (use an LM317 or a 78L05
etc. if needed, and a hexfet or transistor to drive the output, if you
need higher output voltage ratings.)

  Mark

Lalakis Parafyadas wrote:
>
> Hi there. I'm interested in making a 1Hz frequency generator with a NE555
> timer. What resistors, capacitors do I need and how should I connect them to
> the chip? Thanks in advance, Argiris

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