recogicion of a cristal

[bloody-orc]

Hi there

Is there any way and what way to mesure a cristal with a pic. i connect a lets say 27MHz cristal to some pins and then it puls high out 1 but if i put 433MHz cristal to the same pins then it will pull high out nr 2

 

[Nigel Goodwin]

Hi there

Is there any way and what way to mesure a cristal with a pic. i connect a lets say 27MHz cristal to some pins and then it puls high out 1 but if i put 433MHz cristal to the same pins then it will pull high out nr 2

You build an oscillator round the crystal, and use a PIC as a frequency counter to measure the frequency - there are a number of PIC based frequency counter designs (including a very old MicroChip application note).

BTW, you don't get crystals anywhere near as high as 433MHz.

 

[bloody-orc]

nono this 433MHz was an example not a plan to use one.

maybe something from **broken link removed**

or could i use something like that?

 

[bloody-orc]

or maybe this (i guess this is the best)
https://www.electronics-lab.com/projects/test/005/index.html

 

[Nigel Goodwin]

or maybe this (i guess this is the best)
https://www.electronics-lab.com/projects/test/005/index.html

Yes, that's all you need - you could add a buffer from the emitter of T1 to feed a frequency counter (a PIC one would be good enough). Bear in mind though that this circuit only oscillates at the crystals fundamental frequency, so a 27MHz crsytal might run at only 9MHz (for a third overtone crystal).

 

[bloody-orc]

no thats no problem at all. all i need to do is tu understand that it is a 27MHz cristal.

 

[mstechca]

You could compare frequencies.

write your code so that one output pin is pulsed throughout your program, or better yet, try to take the pulses directly from the crystal itself.

Once you get a pulse, make yourself another oscillator. Both of these oscillators make an input of a digital PLL.

I think the simplest way to go with the PLL design is to connect one input to one input of an xor and xnor gate, and the other input to the other input of an xor and xnor gate.

connect the outputs of these gates to separate indicators. Two LED's with current limiting resistors will do.

The reason why I say use xnor and xor is because 1 LED will tell you when the frequency is the same and both oscillators are outputting different polarities, and the other LED will tell you when both oscillators are outputting the exact same signal.

both LED's cannot be on at the same time.

 

[bloody-orc]

well as i use 8 different crystals to make high 8 different outputs then i guess i really cant use that