I'm new to electronics but trying to fumble my way into understanding all this. One aspect of a project uses a CD4060 IC to provide a 4 Hz signal to the Arduino (the schematic is here: http://joelbrown.ca/tablehockey/Clock/Clock_button_schematic.jpg). I'm using a 32.768 kHz crystal with capacitors and resistors to provide the timing for the signal (I sort of figured out how to determine the load capacitance for the crystal). However the project and different data sheets indicate different values for the resistors. How does one determine the proper value for one's application? For instance the project schematic advises using 10 M ohm and 470 k ohm resistors with the capacitors and the 32.768 kHz crystal, page 4 of this datasheet http://electroschematics.com/wp-content/uploads/2010/02/CD4060-Datasheet.pdf advises using 15 M ohm and 330 k ohm resistors, and page 5 of this datasheet http://www.onsemi.com/pub_link/Collateral/MC14060-D.PDF advises using 18 M ohm and a 750 k ohm resistors with a 32 kHz crystal. The Texas Instrument's datasheet from the actual IC http://www.ti.com/lit/ds/schs049c/schs049c.pdf tells me even less. Is there a resource I can reference to better understand what is going on here?
Thanks
The resistor values are not very critical. The parallel resistor should be as high as you can easily get, which is probable 10M if you are shopping at a component store. I used 33M in one design, but that's because I was looking to get the current consumption as low as possible (the circuit worked just fine with 10M but consumed another quarter of a microamp or so). I suggest 470K or 680K for the series resistor, either should work.
I'm rather sure the actual values of those resistors do not matter ( not sure if even an infinite ( omitted ) parallel resistor would work ).
I rather doubt if I should run those CD40xx at 9V, as http://joelbrown.ca/tablehockey/Clock/Clock_button_schematic.jpg suggests,
and just feed the (9V) signal into a 5V Arduino ?
I understand those CD40xx can run at 5V as well.
Or is it rather advisable to activate the pullup resistor and drain 5V into the CD4060 or CD4021 ?
Or doesn't it matter at all, as there's no real current flowing ?
Is there a resource I can reference to better understand what is going on here?
Those numbers are within the ball park and they don't need to be that precise. Rf is usually 1M - 15M, higher for low frequency crystals. Rs is usually 100k - 470k, higher for low frequency crystals.
A word of caution: 32k crystals are difficult to get to work reliably. and I have never had any luck getting them to work with HC4060 (never used CD4060). So if I were you, I would try them out first before committing to such a design.
Thanks everybody! I can now check off one of the zillion unkowns I have with this project.