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Si5351 as ultrasonic driver/transmitter

the00

Jun 8, 2023
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Hi all,
I want to use the si5351 to drive an 40kHz ultrasonic transducer; I already built a fixed frequency transmitter circuit, but I need to adjust the frequency, hence the si5351. Does someone know if it's possible to directly connect the transducer with the clock out pins of the si5351?
Any hints would be much appreciated, thanks in advance!!
 

kellys_eye

Jun 25, 2010
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Does someone know if it's possible to directly connect the transducer with the clock out pins of the si5351?
No. You'd need to buffer the signal.

How accurately do you need to adjust the frequency? The device needs to be programmed using its I2C interfacce and therefore require 'running' software to constantly update the device registers to change the frequency.

Probably easier to use a simple 4MHz crystal and logic (CMOS) divider to get down to 40kHz - tweaking the crystal is possible using a trimmer capacitor that allows 'some' variation around the fundamental - depends on the range you need.
 

Delta Prime

Jul 29, 2020
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I have used that exact same method in the past with success but I have also experienced that the capacitance given a 4MHz crystal and logic (CMOS) even with a trimmer is far from resonant frequency it is just an electrical capacitance I had to use a matching network to the transducer a series connected inductor is what I used so in essence I had to use a buffer for a buffer.Also.. My 4 MHz Crystal which I installed in close proximity to the transducer suffered dielectric breakdown & mechanical fracture. In my case it was due to poor architecture, my placement of the components themselves so be careful but other than that it's been 4 years runs perfectly.
 

the00

Jun 8, 2023
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I have used that exact same method in the past with success but I have also experienced that the capacitance given a 4MHz crystal and logic (CMOS) even with a trimmer is far from resonant frequency it is just an electrical capacitance I had to use a matching network to the transducer a series connected inductor is what I used so in essence I had to use a buffer for a buffer.Also.. My 4 MHz Crystal which I installed in close proximity to the transducer suffered dielectric breakdown & mechanical fracture. In my case it was due to poor architecture, my placement of the components themselves so be careful but other than that it's been 4 years runs perfectly.
Do you have a schematic for your project and would be willing to share it here? Would help a ton!
 

Delta Prime

Jul 29, 2020
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Do you have a schematic for your project and would be willing to share it here? Would help a ton!
Four years is too long for me to keep schematics lying around. But I remember exactly what I did. I have no problem drawing you one up it'll be a while more likely next week I'll pencil you in the schematic be patient.
 

Delta Prime

Jul 29, 2020
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Harris HA7210 Crystal Oscillator IC
1687011686546.png
This is an inexpensive and versatile IC which provides a useful design option halfway between discrete crystal oscillator circuits and fully integrated oscillator ICs containing their own on-board crystals


This is a general purpose circuit that may be useful in some simple applications, but for a circuit needing a divider, or total reliability, some of the following solutions may be better.
A 4060B Crystal Oscillator


1687011102760.png
This is one of the cheapest ways to construct a crystal oscillator, using a single inverting logic gate

photo_1687001945169.png
 
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