Electronics > Beginners
1 HZ generator based on crystal (32.768 khz) issue
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Mate_Well:
I'm planing to build a digital clock with 7 segment and BCD outputs, that part should work (will work on it later, a bit irelevant atm) and i need to make 1hz clock signal, lookedonline if there is better option then555 timer that would be more acurate, and i found one that "divides" 32.768khz to 2hz and in next "stage" it chops it further to 1hz (bingo right?) Built it on breadboard and worked fine, and thus decided to build it on a veroboard ("cracker" with copper dots), and it didn't work  (even thought i checked all conections 10 times) after a minute or 2 (i accidently forgot to disconect it from psu) it started to work fine... for 30 seconds or so, then stoped. i have been trying to make it oscilate with no luck (hocked up a led after 1st "diving stage") only low frequency when i phisically touched one of the pins for the crystal, probably mains frequency coupled. Soo i decided to make 2nd board (the 1st was a chaos after trying to make it work) without the 2nd "stage" (2hz to 1hz) checked everything like 50 times just to be sure (last crystal i had) and behold nothing, same issue. When i touch anything from pin 10 to crystal (or pin 11) it couples the mains on it, i have zero idea what could be wrong, i checked every single thing and nothing made the 2nd board work ( the 1st board "worked" like 2 times and both were flukes, that jabaited me soo hard ;[ )  i will send picture of the board tomorow (and i have done my best to put all of it close together to minimalise other "factors")

in short : issue with 32.768 khz to 2 hz "divider" (4060 based), worked on breadboard, no oscilation and "works" when ac coupled by body (except the fact that i got 50hz instead of 32.768khz) (all parts from trustworthy shop)  |O

scheme is in attachments (gray part was not done on 2nd part, since it needs the 1st "stage" to be working), and all values are same, voltage will be 5V and soo i tested it on 5V, only difrence is that i have got 4060B (and i have not found any difrence on interned betven them) (datasheet : https://www.gme.cz/data/attachments/dsh.427-167.1.pdf )

Thanks in advance o/
iMo:
C1 and C2 are rather high. The 32kHz watch resonators are designed for a single 6 or 12pF capacitor. afaik.
Benta:
^^^

What imo said.

Normally you don't need any caps on a 32k crystal, the input capacitance of the CMOS IC is sufficient.

Mate_Well:
Thanks i will try to put 2 in series or 3 in series (if i have that many) and if that fixes it it would be golden, and i didn't gave 2nd look to the values tbh, only the 6M8 resistors semt big to me (no point of refecne when it comes to crystals)  (and would be +1 to wrong cap value strugle counter, had isseu with too small cap value on 555s)
Edit: or try without one as Benta said TY
iMo:
The parasitic capacitancy of the 4060 (plus package plus wires) pin is around ~6pF, therefore try it first without capacitors. In case you would need to tune, you may try with a gimmick capacitor (a 5mm short long 0.2mm thin twisted wire) wired to the 4060's xtal oscillator input.
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