Peizo harvesting what is the perfect transducer for my application freq. vs Length?

My plan is to generate power from inside a collar of an elephant using Piezo.



I am new to Piezo harvesting. my plan is to fix a little weight at the end of Piezo and make it vibrate as elephant moves. I understand as I fix weight to the end the natural freq. of Piezo stick is brought down. But how far can I bring it down? from 60Hz to 10Hz?

here are the Piezo's I have as choices.

**broken link removed**
the ones with lower freq. are smallr in size. makes me wonder if I should get a bigger one with higher freq. and lower the natural freq. with the help of weights.

Please advice.

it will be a lot helpful.

The graphs show the frequencies which result, as you increase the weight on the unit. The graphs do not go down as far as 10Hz. I imagine the manufacturer found that the weight has to be heavy enough that it breaks the unit in a short time.

The graphs show the frequencies which result, as you increase the weight on the unit. The graphs do not go down as far as 10Hz. I imagine the manufacturer found that the weight has to be heavy enough that it breaks the unit in a short time.

Click to expand...

You may be able to design a fixture with a stop that limits the deflection range. But the available power will be reduced proportional to resonance frequency, leaving about nothing at low frequencies.

For low frequencies, electromagnetic generators (linear or rotating with excenter mass) are more promising, I think.

I think you should look into methane harvesting, but the
elephant may mistake your intentions ;p

Dear everyone,


thank you for your replies, here is a reply I got from the company.

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Hello Amalinda,

Thank you for your interest in our products. I think your best bet is going to be trying a couple different products. It is going to be less about tuning the products to match the exact natural frequency (since I am assuming the movement of an elephant can somewhat inconsistent at least when compared to a motor for example) and more about loading the products up with enough mass so that they strain (therefore provided a voltage/energy) whenever the elephant moves/walks etc. I would try the V25W and the V21BL. The V25W is larger and has a high natural frequency but is the thinner of our two larger products and with enough mass should be able to bend and strain when the elephant moves. The V25W should give you the most energy as it has the most amount of piezo. The V21BL is longer and therefore it will be easier to get it down to the lower frequencies but it will still take a decent amount of mass on the tip of the beam.

I am not sure if you are familiar with our datasheet but I have included a link here. It has some good detail about what you will need (clamping the product in a cantilever configuration, how to tune/attach tip masses etc.) Any questions please feel free to email me directly.

Volture Datasheet:**broken link removed**



Regards,
****



-----Original Message-----
From: amalinda [mailto:am****.gamage**m]
Sent: Wednesday, March 26, 2014 5:23 AM
To: Sales and Service
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Message:

I need a peizo device to harvest energy from inside a collar of an elephant.

I intend to change the natural freiqncy by adding weights to the end of the Peizo.

I know you have a coupel of Piezos available but I dont know which one to chose.
I would like to buy the biggest one, but its natural frequency is a bit too high. Can I get it and reduce the n.f by adding weights or should I get the small one made for smaller frequencies?

Please advice.
awaiting your reply.


************************************

Sender's Details:

First name: amalinda

Email: ****ge**com

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How did you hear about us:

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Dear FVM,

electromagnetic generators? where can I find them. Can you please direct me to a couple of shops or a shop I can get them from? In my country those dont exist. And what do you mean graphs? whoch graphs? i didnt notice any graphs in the pdf. please tell me where.

and everyone,
And what do you guys think about the reply from the company?


And really, methane Harvesting? you're joking right? because im kinda in the state to take anything very seriously.

1.

The reply seems to say 'No guarantee our product will work with your project. Try one model, try the other, see which works best.'

2.

Thinking further about how to extract electrical power from an animal's unpredictable movements, my memories drift back to the time I owned a self-winding wristwatch. Inside was a loose weight which rattled around as my arm moved, and kept the watch wound.

Electrical versions were developed. A similar method may provide sufficient power for your project. I believe our arms have a frequency of motion which is not too different from an elephant's.

https://en.wikipedia.org/wiki/Automatic_quartz

Excerpt:
"As the wearer moves, the pendulum turns and spins the pinion at a very high speed - up to 100,000 rpm. This is coupled to a miniature electrical generator which charges a storage device which is a capacitor(s) or a rechargeable battery."

Dear BrathheRad,

thank you for your time.

I agree to what you pointed about their reply to me. But I guess its a good option to try and see what happens. I will try. because right now, I dotn have too many options. I have already implemented Solar harvesting. Thermal Harvesting will be easy to implement. but Kinetic is the hardest.

I would love to use the method used my Seiko. But where am I going to buy the aparatous? is there any place online I can buy such a system?
Do you suggest I remove it from a watch?
if you know a place I can buy such a device please let me know.

I think the latter method best suits but the lack of availability of the devices to test is the biggest problem to me?
do you have any idea?

Amalinda said:

I would love to use the method used my Seiko. But where am I going to buy the aparatous? is there any place online I can buy such a system?
Do you suggest I remove it from a watch?
if you know a place I can buy such a device please let me know.

I think the latter method best suits but the lack of availability of the devices to test is the biggest problem to me?
do you have any idea?

Click to expand...

Come to think of it, I have never seen a standalone unit which converts motion to electricity in the same manner as a self-winding watch. I suppose it is proprietary technology, a 'trade secret' of the watch manufacturers.

I think I saw the word 'quartz', which suggests piezo (similar to the unit you are considering).

Conceivably you could dismantle a self-winding watch, and connect your project to the power leads. It would require skills and knowledge and equipment, suited to deal with tiny components.

However even if such a feat is within human ability, the watch's power is probably insufficient to power your project.

A linear induction design, similar to an induction flashlight, would probably be much more suitable. How much power do you need to generate, on average?

I have fulfilled my power requirements by appropriately attaching a little solar panel to the Elephants Collar. But I have to harvest Kinetic and Thermal as it is what I must due to the fact my research must incorporate three harvesting methods.
I received a another reply to an email Isent from the Piezo Company I wish to attach it here.
----------------------------------------------------START--------------------------------------------------------
Hi Amalinda,

No problem. Very interesting project, I am a little skeptical that you will get enough energy out of our products to do anything with. However with a lot of the applications that our products are used for it all depends on what your power budget is and how often you will need that power or your duty cycle. I think it will be more feasible to accumulate and store energy from the elephants movement over a decent amount of time and then when there is enough power built up use that power to perform some task ( I am assuming you are monitoring something and then want to record that data or send it wirelessly?)

Good news is it looks like the collar will provide a good place to mount some sort of enclosure that houses the clamped energy harvester and whatever electronics you are using. For a mass I think I would start out with 15 grams or so on the V21BL and maybe double that, 30 grams on the V25W. I would definitely have more mass on hand though and be prepared to add more. Again it is going to be about putting enough mass on the beams of our products so that when the elephant walks the harvester bounces and strains. You could even do small tests by putting the energy harvester on you and after jumping around see what you get out.

Hope that helps.

Thanks,
Brian
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I would be happy if I can get per day 1mA for may be for a total of 30 minutes which enable me to harvest 0.5mAh. I know the output will never be consistant. But a total of this much? Atleast? Please correct me If I am wrong.

Thank you for the idea BradtheRad , about the Seiko watch,
I am not so sure if I will succeed to get the whole circuit out correctly and make it function. And I believe I would get a higher power from a good piezo than from a dismantled watch. Also considering its complexity, I feel a little negative about the thought. But if I am wrong, please correct me.

Dear mtwieg,
Thank you for that Idea! I am going to order some flash light torches from ebay. Either I am going to make my own or buy and as BradtheRad suggested, dismantle that and try to take something from it. I think that will be much easy for me and risk less as well.
I have an idea to buy around 5 of these and combine them and make a much stronger one. Do you think it will be a good idea?

Shall I also try to make my own?

Thank you for your time.

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Amalinda said:

Dear mtwieg,
Thank you for that Idea! I am going to order some flash light torches from ebay. Either I am going to make my own or buy and as BradtheRad suggested, dismantle that and try to take something from it. I think that will be much easy for me and risk less as well.
I have an idea to buy around 5 of these and combine them and make a much stronger one. Do you think it will be a good idea?

Shall I also try to make my own?

Thank you for your time.

Click to expand...

An linear induction harvester is literally just a strong permanent magnet (grade 52 NdFeB is the strongest commonly available) sliding through a solenoid. It's a very trivial thing to build. The only complicated part is how to store the output energy effectively. Are you planning on using batteries, or supercapacitors? But it should be capable of delivering much more power than a piezo, since the magnet can be much heavier.

Dear mtwieg,

Thank you for your reply.

So 52 nDFeB is one of the strongest types! Good to know. Do you recommend a place I can get them from other than ebay? Yes, I am planning on maki ng my own and testing how effective its going to be. Do you have any sort of tutorial or guide lines that I may need to follow? Im jusrt thiking having a coil around a solenoid magnet and allowing the magnet to move. I understand the more coil I put and stronger the magnet I get more electricity. and of course the Speed of movement! I will try to optimise those. Is there any parameter I missed?

I am using a LiPo battery. I can use some kind of a harvester IC or if the power is less than 380mW I can sue the existing TI BQ25504 ICs to connect the induction Harvester. it has max 5V Vin. I dont think the Induction harvester will give me more than 380mW. or will it?

I dont mind the magnet being heavier as long as its shape is solenoidal.

Once again thanks for the info, the magnet type is going to be very useful to me. If there is a stronger one please let me know.

I agree the magnet in a solenoid is your best bet. You can even wind your own.



Super-magnets come in a variety of shapes and sizes. A convenient one for you to use would be cylindrical, 1 inch x 1/4 inch.

The magnet ought to return to the center of the solenoid when idle. Therefore I picture springs anchoring each end. It is important that the springy action be weak enough so the magnet can easily travel up and down an inch or so, yet suspended so it returns to the center of the solenoid.

The springs I would try first are the ones found in retractable pens. If the first is too stiff, the next may be just right.

Dear BradtheRad,

I attended a coference **broken link removed** two days before. I in that I found a similar device. They have used two v.strong magnets instead of the springs you have used. so there are three magnets! one is very smoothly moving inside a tube like solenoid with the help of two other magnets at two corners.

and the middle magnet placed inside the coil (as shown in your figure) was placed towards the END of one side of the coil. he said through practice he figures he gained more voltage/current by placing the magnet towards one end of the coil instead of placing in at center.

What is the logical explanation to this?

thank you.

The voltage is generated by varying the magnetical flux in the coil, not the movement as such. Moving the magnet in the coil center doesn't change the flux in a first order.

Fvm,
I get the idea. I think I wasnt clear in the earlier response. thank you for your explanation.

Dear All,


https://e-magnetsuk.com/magnet_products/
**broken link removed**

I think those two companies sell good magnets of different types and sizes.

I think for me now it has boiled down to the best configuration. I believe I should use the best configuration with the most suitable shape of magnet to harvest most power.

Right now I am thinking of having a solanoidal magnet placed inside a coil. I wish to move the magnet or coil. I haven't harvested power this way so I guess this is good.

I notice there are many difference sizes and shapes.
E.g.
Ring type
Solanoidal
Coin type

It makes me wonder if there would be a better configuration (using any other shape) that I can chose to harvest better energy by forcing larger amount of flux through coils. And if possible, advice me the best way to start off. is it by moving the magnet keeping coil still or vice versa? However I will try both and post my results here as I continue further.

so, before proceeding to buy,
I would also like to know, the importance of two parameters to my application of a magnet.

1. Pull Force(Lbs):
2. Surface Field(Gauss):

I know 1st is very important. but Im doubtful about the second one.

if any of you know, please advice me.

thank you.

Amalinda said:

Dear BradtheRad,

I attended a coference **broken link removed** two days before. I in that I found a similar device. They have used two v.strong magnets instead of the springs you have used. so there are three magnets! one is very smoothly moving inside a tube like solenoid with the help of two other magnets at two corners.

Click to expand...

Sounds fine. My reasoning for using two springs, was that they would suspend the magnet, and hold it away from the walls of the tube, reducing friction (to some extent anyway).

and the middle magnet placed inside the coil (as shown in your figure) was placed towards the END of one side of the coil. he said through practice he figures he gained more voltage/current by placing the magnet towards one end of the coil instead of placing in at center.

What is the logical explanation to this?

thank you.

Click to expand...

The ends of a bar magnet have the strongest magnetic fields. So perhaps it is more effective to position the stronger part of the magnet in the middle of the coil, where it will spend more time traveling at the highest speed.

Thank you people! Stanford Magnets agreed to sponsor a couple of magnets for my project. Can you believe they have 4 inch by 4 inch magnets that can lift 500KGs? Unbelievable. Im going to order some and play around and find the best ways to harvest kinetic energy.
I am happy and so grateful for your guidance, EVERYONE!

I will update my progress here.

you guys rock!!