Help buying a sensor for a senior design project

Thread Starter

Paul Nguyen 1

Joined Feb 27, 2019
7
For my senior design project, I need to buy a piezoelectric sensor. I was wondering which one I should buy? I'm having issues looking for some online.

For the project, basically We have a circuit with an LED connected to a piezoelectric sensor. This would be submerged in water. We would then use an immersion transducer to send ultrasonic waves to the device, the waves would hit the sensor activating the piezoelectric effect and send energy through the circuit to turn the LED light on/off.

It doesn't necessarily need to be a piezoelectric sensor, but thats what my group figured we could use. If there are better sensors we can use that serve the same purpose, we can buy that instead. We are focusing on making the circuit, so our mentor told us to just find a sensor online to buy and use. Also if submerging the device in water is too difficult because of the water absorbing too much energy, we can also do the test in just air.
 

Uilnaydar

Joined Jan 30, 2008
118
As I tell my interns when I give them a project. Did you search Digikey for <insert part I recommended here>.

See if whatever you find will work in your application. Once you have an idea head back here with a proposed schematic and we can help.
 

Thread Starter

Paul Nguyen 1

Joined Feb 27, 2019
7
Hi, I just searched digikey for the sensor. I was only able to find sensors that were used in flow detection applications. So I wasn't able to find a sensor that would work in the application for this project. Do you have any suggestions on what other sensor I could try and look for that will work for this project?

The sensor we buy must also be somewhere in the 1Mhz-5Mhz range.
 

Thread Starter

Paul Nguyen 1

Joined Feb 27, 2019
7
That sounds like you're hoping to actually power the LED with energy from the piezo sensor. I hope that's not true?
We would have a power supply on the circuit board to power the LED, The energy from the sensor would just be used as like a signal to to turn the led on/off.
 

pmd34

Joined Feb 22, 2014
518
Hi P, most piezo systems use some sort of resonance based on inductive and capacities nature of the piezo element. The element itself is made so it has a particular natural resonant frequency around the region where you will operate it, and this is normally at 40kHz. MHz piezo elements seem to be very rare. So you may have to look to other ways of detecting.

You may also have to get more involved with how you actually recognize the presence of the ultrasonic waves - the presence or absence of a 5MHz signal on the sensor.

For the sensor itself you could.. maybe look at a quartz crystal such as:


These come in a wide range of frequencies. You can cut the tin can off to reveal the element. This should then preferentially resonate at the designated frequency in your system when exposed to it. You would then have to make an amplifier & detector circuit that would acknowledge when it saw a 5Mhz etc. signal.
 
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