Looking for a very cheap clock generator

[Ernst B]

I am looking for a very cheap clock generator (e.g. as an input for a
4020). I don't want to use an oscillator module, since that is too
expensive for my application. Instead I'm thinking of a crystal, a
cap, a transistor and some other simple stuff. Since I only have
experience in digital IC design, I'm seeking for some advice how to
build such a circuit.

Thanks for your help in advance.

Ernst.

 

[Dominic Suter]

Is a NE555 still to expensive? I hope not. This standart timer is really
easy of use and quite cheap. The only disadvantage about it is, that you
can't receive a dutycycle by 1 (50% on and 50% off), but most of the cases,
that doesn't matter.

Dominic

 

[Michael Black]

I am looking for a very cheap clock generator (e.g. as an input for a
4020). I don't want to use an oscillator module, since that is too
expensive for my application. Instead I'm thinking of a crystal, a
cap, a transistor and some other simple stuff. Since I only have
experience in digital IC design, I'm seeking for some advice how to
build such a circuit.

Thanks for your help in advance.

Ernst.

Cost shouldn't be a factor if this is a single project. And if
it is a production item, you need to look at circuit board space
of both scenarios, and the cost of all the components.

Keep in mind that if you are building in quantity, price will go
down.

I'm not sure there is a big price difference between an oscillatorin a can
and a crystal at the same frequency. If you choose the wrong frequency,
cost may go up because it will have to be custom made, whether it is
a crystal or complete oscillator. If you are't on a frequency where you
can get cheap oscillators in cans, then you might want to look at the
overall design and see if something can be changed to accomodate a common
and cheap frequency.

It might be cheaper, depending on the frequency, to go to a non-crystal
oscillator. But you have to make sure that your design does not
need the stability or even accuracy of a crystal. In production,
if you have to adjust something to an exact frequency it may be more
costly overall than a crystal (or crystal oscillator). But if you can
get away with an RC oscillator, then you may find you don't need the
divider, since it's easier (and often better) for an RC oscillator at
a lower frequency. Note that many designs may use a crystal (discrete
or in a prefabricated oscillator) because its cost even with a
divider to get it down to the needed frequency is less than the cost
and trouble of an RC oscillator (especially in a production setting),
even if stability is not an issue.

Michael

 

[Joe McElvenney]

Hi,

How about using the 4060 instead as it has an internal
oscillator circuit and is very similar to the 4020. All you need
for an RC clock are 2-R and 1-C or, for the quartz version, 2-R,
2-C and a crystal.


Cheers - Joe

 

[Baphomet]

I am looking for a very cheap clock generator (e.g. as an input for a
4020). I don't want to use an oscillator module, since that is too
expensive for my application. Instead I'm thinking of a crystal, a
cap, a transistor and some other simple stuff. Since I only have
experience in digital IC design, I'm seeking for some advice how to
build such a circuit.

You might have to touch up the 470pf / 330pf capacitor values depending on
xtal freq.
http://www.militarymags.com/electronics/xtalosc.gif

 

[Baphomet]

This circuit is even better since it should drive the 4020 directly without
having to square up the output.
http://www.ee.washington.edu/circuit_archive/circuits/F_ASCII_Schem.html#ASCIISCHEM_009

 

[CFoley1064]

I am looking for a very cheap clock generator (e.g. as an input for a

4020). I don't want to use an oscillator module, since that is too
expensive for my application. Instead I'm thinking of a crystal, a
cap, a transistor and some other simple stuff. Since I only have
experience in digital IC design, I'm seeking for some advice how to
build such a circuit.

Thanks for your help in advance.

Ernst.

Have you taken a look at ceramic resonators? They're cheaper than crystals,
are as reliable, and have low frequency drift in comparison with anything else
except crystals. If you want a "cookbook" design, look at the datasheet for a
Panasonic general purpose ceramic resonator below. You need 2/6 of an inverter
IC, two small caps, and a 1Meg resistor. These are generally used for
cost-sensitive microcontrollers, and are more than accurate enough to clock
serial comm and most other things (+/- 0.5%).

http://www.maco.panasonic.co.jp/www-data/pdf/APA0000/APA0000CE2.pdf


Good luck.
Chris

 

[Glenn Gundlach]

I am looking for a very cheap clock generator (e.g. as an input for a
4020). I don't want to use an oscillator module, since that is too
expensive for my application. Instead I'm thinking of a crystal, a
cap, a transistor and some other simple stuff. Since I only have
experience in digital IC design, I'm seeking for some advice how to
build such a circuit.

Thanks for your help in advance.

Ernst.

Have you looked at CD4060 ? Similar bug with internal oscillator.

http://www.ee.washington.edu/stores/DataSheets/cd4000/cd4060.pdf

GG