[General] HC-SR04 strange crystal oscillator value

[micromolvi]

I bought an HC-SR04(ultrasonic range finder) from a local shop, that I intend to interface with a microcontroller. It looked like original but when I saw its images on google I noticed that the crystal value were different.

HC-SR04 that I have, has a 20.945Mhz crystal whereas the images on internet show a 4Mhz crystal

I am confused if its a fake version of HC-SR04.

Can someone tell me if the timing characteristics of input and output will be the same for this device like the original one.

If not how will I determine the correct timing characteristics?

 

[udayan92]

HC-SR04 that I have, has a 20.945Mhz crystal

I did not know that the said sensor can have that high a frequency value.Mostly a 4MHz crystal is used.
For reference,when I had to interface the said sensor to my microcontroller (PIC16F877A),I used a prescaler of 8 to divide the on board freq. reference for the microcontroller from 12MHz to 1.5MHz. If you are using 12MHz freq. reference for your microcontroller,it should work without any hitches,I guess....
Try connecting the sensor directly without any prescaling and see what happens.

 

[paulfjujo]

Hello,

I think you are talking about the quartz installed on the HC-SR04 board, not on your PIC develpment board.
Maybe you have a different version of HC-SR04 , but at least, only check if ultrasonic emitter send a burst of 8 cycles at 40KHz !
i don't have any value written on my quartz, so i don't know it...