Using piezoelectricity for data transmission.

[great_sushi]

I am starting my 3rd year in September and I've decided to start thinking about research topics early. I'm quite interested in piezoelectricity along with it's discovered and perhaps undiscovered applications. This is my first idea;
I have watched a lot of nature programs and I have seen that the tracker devices they use to monitor the whereabouts of various animals are always extremely bulky and in my opinion not very nice for the animal.
I am interested in researching into a small compact tracker device for animals using piezoelectricity. I was wondering what you thought about this?

Charging a capacitor using a piezoelectric crystal and the animals motion.. then once charged it releases a pulse. Instead of having to emit constantly thus wasting energy.

Could the system be two-way.. i.e. charges through piezoelectrity then once the capacitor is charged the energy is then released through the piezoelectric crystal. The change in the crystals shape causes a high frequency wave to be produced and transmitted.

Is this viable?

 

[Vanadium 50]

There are applications of piezoelectricity to produce small amounts of power. I know enough to know that there are pros and cons of this. Have you done a literature search? That should be your first step.

 

[Bobbywhy]

great sushi,
You raise several separate issues, each requires a response.

1. These monitoring systems are examples that do not require the animal to transmit anything, thus no electric power is necessary. Many animals, both large and small, plus many insects are now being tracked by scientists studying their behaviors. Some schemes use simple passive reflectors, similar to bar codes, on honeybees. When they pass in and out of the hive they must pass through a “reader”.
http://www.dailymail.co.uk/sciencet...-forcing-dance-streetlights-falling-dead.html

Kin-selection theory underlies our basic understanding of social evolution. Nest drifting in eusocial insects (where workers move between nests) help is greatest. By using a novel monitoring technique, radio frequency identification (RFID) tagging,
http://www.ncbi.nlm.nih.gov/pubmed/17240339

2. Other tracking devices do transmit data, so these require the animal to carry the battery to power the transmitter. Biotrack is a company of dedicated biologists with over 30 years of experience in radio tracking and radio tag manufacture. They supply tracking devices for amphibians, fish, birds, invertebrates, mammals, and reptiles. See their website:
http://www.biotrack.co.uk/
Be sure to check out their smallest and lightest radio transmitter:
http://www.biotrack.co.uk/small-beeper-transmitters.php#s3

In your post you mentioned “Charging a capacitor using a piezoelectric crystal and the animals’ motion”. While this is possible, be advised: the amount of electrical power available it extremely small. Yes, there may be some instances where the tiny batteries already in use would not suit the experimenter’s needs, so there can be a use for “piezoelectric energy harvesters” mounted on animals and elsewhere. And, there are some special applications where the mechanical pressure waves in the local ambient environment are being harvested to recharge a human heart pacemaker battery, for example. Here on Physics Forums there have been several threads discussing this topic thoroughly. For instance, see:
https://www.physicsforums.com/showthread.php?t=691529

And, in particular, see this website from our PF member “old jim hardy”: http://www.designnews.com/author.asp...dfpLayout=blog

You may gain new information by researching the basics of energy harvesting using piezoelectric materials. Notice I did not use your term “crystal”. That’s because there are many materials that are piezoelectric, including very flexible thin films. I suggest you start with Wikipedia.

3. All piezoelectric materials are “two-way” as you mentioned. Consider them transducers: they convert one form of energy to another. A microphone is an acoustic transducer, converting mechanical sound wave energy into electrical energy. But we would not apply a high powered amplified signal to a microphone to play our music. A speaker is designed for that. In sonar, for instance, an image of a baby in the womb is created using ultrasonic frequencies. A single piezoelectric crystal-like ceramic is used for both transmission and reception. A high voltage pulse of AC electrical energy at the resonant frequency of the crystal is applied to the crystal. The crystal vibrates and emits ultrasound. The pulse passes into the body, is reflected by various materials, and the echo returns to that same crystal. Now, the mechanical acoustical pressure waves cause the crystal to vibrate (because it’s resonant at that frequency) and thus it generates a small output voltage. This voltage is then processed by the receiver to generate an image of the baby. Try to Google “sonar” or “ultrasonic imaging”.

Now, one might build a piezoelectric transducer which converts the mechanical energy from the wingbeats, say, of a bumblebee at 120 Hertz into electrical energy, then harvest that energy to store in a capacitor or battery. But when you wanted to transmit some data back to your receiver/data collection point, your piezoelectric transducer is resonant to 120 Hertz! Normally radio frequencies are used for this purpose, so that piezoelectric could not act as a “two-way” transducer.

 

[great_sushi]

Ok thanks a lot! This info is really helpful I will research into what you have mentioned.

Just out of curiosity could you have a piezo material attached to a circuit with a capacitor then once the capacitor is charged the circuit switches to another with a specific resonant frequency?
I am right in thinking that circuits have resonance?

 

[Bobbywhy]

Great_sushi, I cannot understand what you’re asking above.

You are right: circuits can be resonant. See this thread from here on Physics Forums:
“What is resonant circuit? and specifically what is RLC circuit?”
https://www.physicsforums.com/showthread.php?t=101556

And then, please study this Wiki page: http://en.wikipedia.org/wiki/LC_circuit

After learning about both physical resonance and electronic resonance please rephrase or re-think your proposal. Then please describe your proposed scenario in more detail and post your question(s) here.