Selecting load capacitors for crystal without datasheet

Thread Starter

hrs

Joined Jun 13, 2014
355
Do you know the manufacturer of the crystal? Check for a logo.
There are only the markings as shown in the photo of post #11.

I got a tuning fork crystal and swapped it for the other one. With 15p and 20p it starts immediately. I may try some other values to see when it stops.
 

DickCappels

Joined Aug 21, 2008
8,178
I missed that detail. The marking is 32.768000 which I take as 32.768000 MHz. As has been mentioned, this would be an unusual package for a 32768 Hz crystal (notice no decimal point is needed).

I do not recognize the logo.

The ones I buy from S.E. Asia through a Citizen distributor look like this:

1627388966519.png
1627389015780.png
 

sarahMCML

Joined May 11, 2019
42
There are only the markings as shown in the photo of post #11.

I got a tuning fork crystal and swapped it for the other one. With 15p and 20p it starts immediately. I may try some other values to see when it stops.
The HC49U crystal you originally tried appears to be from Comtec-Crystals of Germany, and is definitely 32.768MHz. I've attached the data sheet (I hope!)

Sarah.
 

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Ian0

Joined Aug 7, 2020
4,168
I have to admit that if I'm at work, I use 22pF, because there is a big reel of 1206 sized 22pF NPO capacitors which was bought before I started the job; and if I'm making something at home I use 15pF (because I have a big reel etc. etc.)
I've never found one that failed to oscillate, except when I added them to a DS1338 which already has them built in.
 

Thread Starter

hrs

Joined Jun 13, 2014
355
I have to admit that if I'm at work, I use 22pF, because there is a big reel of 1206 sized 22pF NPO capacitors which was bought before I started the job; and if I'm making something at home I use 15pF (because I have a big reel etc. etc.)
I've never found one that failed to oscillate, except when I added them to a DS1338 which already has them built in.
After swapping the MHz crystal for the kHz crystal I experimented with several values and too found that it's actually quite tolerant. The phase of the moon doesn't enter into it after all!
 

Ian0

Joined Aug 7, 2020
4,168
After swapping the MHz crystal for the kHz crystal I experimented with several values and too found that it's actually quite tolerant. The phase of the moon doesn't enter into it after all!
Crystals are mechanical resonators, so the higher the resonant frequency the smaller they are. . . . .
 
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