Argiris,

If you need an astable operation the formula is:

f= 1.443/((Ra + 2Rb)C)

and the circuit is:

Ra between pin 7 and 8 (8 and 4 to Vcc, 3 to 18V)
Rb between pin 6 and 7
C   between pin 6 and gnd.
pin 6 to pin 2.
pin 5 to a CAP (0.1 uf) to GND.
pin á is the output.

Hope this help.

Daniel Bernal
daniel@bernal.com

-----Mensaje original-----
De: James Paul <jim@JPES.COM>
Para: PICLIST@MITVMA.MIT.EDU <PICLIST@MITVMA.MIT.EDU>
Fecha: Martes, 07 de Diciembre de 1999 10:45 a.m.
Asunto: Re: [OT]: 1Hz frequency generator with NE555 timer


>  Argiris,
>
>  I can't tell you right off hand what parts to use with a 555
>  to get a 1 second timer, but the 555 may not be all that
>  accurate.  If it were me, (and it was me not too long
>  ago), I would use one of the 8 pin PICS.  I used the 12C672
>  because thats what I had at the time.  With this part, you
>  can use the internal 4 Mhz oscillator and not have any external
>  parts to contend with.  You would have +5, Gnd, and an output.
>  Plus you'd have 5 more I/O pins available for more outputs,
>  complementary outputs etc.  The cost is about the same for
>  each.  I will probably never use a 555 timer again.  The 8 pin
>  PICS are much cleaner, and somewhat more accurate when using
>  the built in RC oscillator.   And you can have several outputs
>  working at the same time.  And each can be different if need
>  be.  IMHO the PIC is a better choice.  If you've never worked
>  with a PIC before and need help, don't hesitate to ask.
>
>                                           Regards,
>
>                                             Jim
>
>
>
>
>On Tue, 07 December 1999, 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
>
>jim@jpes.com