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From: cs911225@ariel.cs.yorku.ca (KEN E WILLMOTT)
Subject: Re: A very STABLE 40khz generator (was IR receivers)
Message-ID: <CJFxE5.A22@ariel.cs.yorku.ca>
Sender: news@ariel.cs.yorku.ca
Organization: York University, Dept. of Computer Science
References: <CJ83IL.Isn@ariel.cs.yorku.ca> <2gqhdu$k4v@handler.Eng.Sun.COM> <sasrer.758213811@cinnamon>
Date: Tue, 11 Jan 1994 00:58:53 GMT
Lines: 69

There is a slight technical problem in an otherwise ingenious
circuit just posted here. It goes as follows:

>A circuit that I have used before is based on the CD4060 (14stage binary
>counter) and a 640Khz ceramic resonator. The CD4060 is basically an
>oscillator and a ripple counter to divide the 640khz down to something more
>usable.

>Here is the pinout of the CD4060 (frequencies are assuming a 640khz
>input signal into pins 10/11/12 - circuit shown below):

                       +-\/-+
              160hz  1 |    | 16  Vcc
               80hz  2 |    | 15  625hz
               40hz  3 |    | 14  2.5khz
              10khz  4 |    | 13  125hz
              20khz  5 |    | 12  \
               5khz  6 |    | 11   >---- see sub-circuit below
              40khz  7 |    | 10  /
                GND  8 |    |  9  NC
                       +----+

>Sub-circuit for a 640khz ceramic resonator:

              12 >----------------------+   
                                 740pf  |    (you may be able to obtain
              11 >-------+----+---|(----+     a resonator with builtin
                         |    |         |     capacitors and three leads)
                640khz  ---   \         |
                 res.    O    / 1Mohm   |
                        ---   \         |
                         |    |         |
              10 >-------+----+---|(----+
                                 740pf  |
             GND >----------------------+


>This circuit has proven to be VERY stable, and is fairly inexpensive (about
>$1.50 for the CD4060 and 640Khz ceramic resonator).

>--
>---
>Rodney Radford          || Computer Graphics/Imaging
>sasrer@unx.sas.com      || SAS Institute, Inc.
>(919) 677-8000 x7703    || Cary, NC  27513




You're like me and like this little gem, right?
Okay, then, how about a VERY, VERY stable circuit? :-)
You really should include a resistor as shown in the diagram
below, don't ask why, just do it!


              12 >----------------------+   
                                 740pf  |    (you may be able to obtain
              11 >-------+----+---|(----+     a resonator with builtin
                         |    |         |     capacitors and three leads)
                640khz  ---   \         |
                 res.    O    / 1Mohm   |
                        ---   \         |
                         |    |         |
              10 >-\/\/\-+----+---|(----+
                   330ohm        740pf  |
             GND >----------------------+


	-Ken Willmott
