Electronics > Beginners
1 HZ generator based on crystal (32.768 khz) issue
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MagicSmoker:

--- Quote from: Mate_Well on October 27, 2019, 09:38:32 am ---ok will do that the issue is i don't have an osciloscope, will try to do and "judge" it with led acrod pin 8 (ground) and 7 (after 1st divishion (that is ofc when it doesn't work))
--- End quote ---

It probably wouldn't do you any good, anyway, because the capacitance of the scope probe is significant compared to a crystal's load capacitance. It is usually the case that touching the probe to one of the crystal's pins either causes it to start oscillating when it wasn't or vice versa.


--- Quote from: Mate_Well on October 27, 2019, 09:38:32 am ---and datastheets of crystal :
...
oh and if the crystal is dead (which wouln't suprise me) i don't have any replacement rn, but i have "random" salvaged ones with difrent freqguencies (most likely much higher) can i connect them instead of for testing or will they break ? (without the caps)

--- End quote ---

I checked the first datasheet and it says the load capacitance needs to be 12.5pF - which, btw, is the total capacitance seen by the crystal. The load capacitors are considered to be in series as far as the crystal is concerned, and don't forget there will be stray capacitance added to this from the traces and the IC itself. I would try using 22pF capacitors here.

Mate_Well:
I use CD4060B, and i will try to do the RC oscilator but i have no idea what values to use (looked on a eguasion and should het 1-7hz with 6M8 and 4700uf cap, i have these and should "work" if my math is correct)

Time t = 2 n / f osc = Seconds

n is the selected Q output number
2 n = Q output number = 2 x Q no times Eg. Q3 output = 2x2x2 = 8
f osc = 1 / 2.5 (R1xC1) = in Hertz

32768 / (1 / 2,5 * (6800000 * 0,0068)) = 1,77....... seconds  :scared:

is the result actualy somewhere close reality becouse i have 0 point of refence when it comes to this (personally i would say it would take hours to charg e but idk)


and the 22pf is issue to me, since i would have to order the parts (shipping in czech is like 8€ for parts that cost 0.04 each) and i have tryed 16pf with no luck (worked "better" without one) and sice i have now only 1 crystal with the right frequency that may or may not be working i will probably troubleshoot on RC circuit and if even that won't work i will just say screw this and do temporarry 555 timer instead (since i will be ordering parts in like a month or so and will revisit it then (with the crystal) and with the RC i will try it untill i break the 4060s i have (2 of them, since that is the only thing i can't rly replace until i order more)

TY all for the ideas and explaining

EDIT: soo i have decided to test the crystal and this circuit on breadboard, with the 33pf caps, guess what it bloddy works :wtf: and boards don't, is there a possibilitty that the flux/rosin i used (the uncleaned residue) "shorts" the crystal pins (well shorts relative to the 6M8 since the tracks are close to each other) again the circuit works on breadboard which makes me wonder what could be the issue
iMo:
For you the T=30usecs (for your testing purposes it does not need to be such precise value)

Below the formula (from DS).

For ~32kHz, for example Rx=10k, Rs=33k-100k, Cx=1.2nF-1.5nF 


Mate_Well:
the RC one works fine on breadboard (soo did the crystal one), and haven't tested it on the vero board (partly cuz the 2nd board took last bit of veroboard i had  :palm: )  but i still can't wrap my head around why it works on breadboard but doesn't on vero board. (breadboard works perfectly and when i touch one of the crystal's legs it "pauses", unlike on the veroboard where it is normaly "paused" and i literally need to touch one of the legs for the circuit to do anything (coupled 50hz from mains most likely instead of the crystal's frequency) but that a] is not remotely acurate (instead of 2hz it is more like 0.13hz) and b] is not even remotely practical. soo just to ease my mind and distract myself i have cleaed the residual flux of the board with alcohol (or something like that) and that didn't change anything (as expected, but made the board look a bit new-er)

Edit: and found out that if i turn on my soldering gun (the heavy one with transformer inside, and i use that for all projects atm) near the 4060B it basicaly does 1 "oscilation) (changes the state of the led across pin 8&9 (not the one on board))
and It kinda feels like it is stuck in reset but only for ascilator when on the board (and thus i have put 100nf cap across ground/reset&vcc (just to be sure, and "smoothing" cap never hurted anything yet)) but still wouldn't explain why the same ic works fine on breadboard
iMo:
The stray capacitance of the adjacent rows on the solderless breadboard is around 3.5pF. On your pcb it is much less. Also doublecheck whether your capacitor's and resistor's values are the right ones.
Do not use transformer tesla iron with cmos chips..
Blocking capacitors (ie 100n ceramics) at the chip's Vcc and Vgnd pins are important with cmos logic.
Your problems are pretty standard, we all have them, and we like to debug them :)
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