EAP speaker? here we go!

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WrineX

WrineX

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Joined 2004
#1
Hi i was reading for a while about EAP's electroactive polymers.

And i wondered how to be able to use them as speaker. the major problem i could think of was the fact that it needs a spring to function correctly since the polymer gets squiched , so in fact gets larger or smaller depending on the dc source.

then after i while i found this paper, wich i believe solved that problem in making it a push pull speakers, then menbrame could be anything. the eap's are just used as motor. i also think because the length of the eaps (or width) and ofcource the voltage applied defines the peak to peak excursion in the end. i think its a rather daunting thing to try. i dont say its gone sound beter then a electrostatic or a normal driver for that matter. but it sure looks like fun !

http://202.114.89.42/resource/pdf/5366.pdf


My major problem is im not the best in electronics, and i wondered how can i superimpose, an AC signal from my stepup transformer onto a DC voltage. in the end its you can sort of tune the thing using the DC on the 4 EAP's then add a high voltage AC singal (superimpose). if someone would have a schematic on how to superimpose ac on dc im gone build me one(or try).


heres a nice example on how to make an EAP. this one is round (also example of what i ment with the spring) ofcourse you can make a square one or whatever length

https://www.youtube.com/watch?v=uw8FLgiXsmk



I dont know how fast they can react, it looks prety slow. but apparantly in the paper they used sort of the same , A polymer with carbon on both sides.


in the paper they reach 30Khz, 10k above what is neededs, in fact im more interested in using it as Bass driver and let a proper esl do the top end. aaah well where not even there yet🙂
 
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#3
well just for planar or you mean as in a AEP ? its rather expensive tape i must add. could be another source of the stuff since its a acrylic polymer wich can be compressed to enlarge its surface area. but i dont know if any acrylic film can do the same. because this 3m stuff is expensive 🙁
 
#5
WrineX said:
well just for planar or you mean as in a AEP ? its rather expensive tape i must add. could be another source of the stuff since its a acrylic polymer wich can be compressed to enlarge its surface area. but i dont know if any acrylic film can do the same. because this 3m stuff is expensive 🙁
Click to expand...
How expensive then?

I got a price of 100 Euro for a roll 12 mm x 33 m. That´s 0,4 square meters.

If the prices scale linear, a 200 by 200 mm piece (0,04 square meters) would then cost 10 Euro.

Trouble is that you probably would have to buy a roll of 33 m of the 200 mm tape, and that's 1650 Euro.
 
#7
87 dollar is pretty much in my opinion!

Another elastomer is latex. Getting 70 micron latex is not so hard all be it weird .... A condom it's 70 micron when not stretched, making a balloon type speaker might be not do hard with this material. Stretch it over a round object , put on the graphite. Get it inside out again on the object and do the other side?

Hmm I have to try, or cut it an make a normal planar membrane
 
#9
Aha Thats sounds beter, stil expensive tape 🙂

I might try a baloon or condom soon 🙂 as base material before I sink in euros into a useless project 🙂

I think latex does not work as good as the vhb. But I has let fatigue isues.
But first I have to make a new cascade and hope it outputs enough power. We don't need much since its al about statics, bit I can imagine it might not be as simPle.
 
#14
solhaga said:
Seems to be the same material with different thickness.
They even have the same data sheet.

Thanks for the great links.

This is very interesting:

"The adhesive surface enables multiple stacking of fabricated unit cells for multi-layer structures."
Click to expand...

By the way the 4960 is even cheaper in the 30cmx30cm

And the Roll is even more cheap you get almost 1.5 meters extra compared to the 30x30 cm a 10 pack is as expensieve as the 30x450cm role



yes, i tried one with a latex menbrame , had to make a new HV suplly first. and get my graphite. tobad it failed. first off my capacitors are underated so they began to spark 🙂 have to get some higher rated ones, since i fed them 600 + volt ac from a CFl inverter. i only need 2 or 3 stages i geus to get some high high voltage. so less expensive caps i need. then i discovered i used a bit of glue to ad the graphite, but this became like a thick solid film wich does not help. further i the connections to the graphite i made with alu foil but next time i i will make sure the al foil is not opposite to the coated menbrame on the other side. it will flash over pretty easy. and last the latex condom might even be TO thin. its 70 micron un stretched. when i stretch it it can easy be like 20 or 30. so when high voltage aplied it flash over pretty easy just bfeore one of my caps blew out en started sparking 🙂

one good thing is this VHB can be stretched almost 5 times so when stretching try not to use more then you need in the final size 🙂 also breakdown voltage is much higher of the VHB.



did you read the part of uneven stretching to ? so you can conhtrol wich way it will strain when you aplly a voltage? thats cool i can imagine some sort of AMT design only stretched at the vertical plain. for instance. so it contracts the pleatings
 
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#15
Well i putted the same capacitors in series to battle the max volt rating. made a new menbrame with a balloon. (of wich i hope it was even latex) rubbed the gaphite in etc... connected the whole thing and played with it , i did see a tiny bit of movement at verry high voltages (wich i cant measure) until the dielectric of the balloon gave way 🙂 sparked and splitted my baloon in 2. to be usefull it has to opperate at lower voltagesi think i the voltage i used is rougly 1000 volt with ac with a 3 stage cascade, i recon around 4 kv or maybe even more. when i kept my lead near the other lead it began to ionize the air so 🙁

I think there are two major things that needs to be improved, ofcourse the menbrame, i will need to order some vhb. second i need to order the carbon black as well. its finer powder then i use now since i use graphite wich is sold to lubricate locks, its pretty hard to rub it in and get a low resistance. what i measures was around 120 K Ohm, i know this can be much lower with either the right graphite or carbon black.
 
#16
WrineX said:
By the way the 4960 is even cheaper in the 30cmx30cm

And the Roll is even more cheap you get almost 1.5 meters extra compared to the 30x30 cm a 10 pack is as expensieve as the 30x450cm role
Click to expand...
I reckon you mean 9460 😕

The original VHB mentioned in the thesis is the 4910 but the one that was used in the end was 9460 as you pointed out.

The difference between 9460 and 9469 (and 9473) is only the thickness of the adhesive (and the differences in properties and prices that gives). The liner has the same thickness: 0,1 mm.

9460 has adhesive thickness 0,05 mm and 12'x12' costs 6,8 euro,
9469 has adhesive thickness 0,13 mm and 12'x12' costs 9,0 euro,
9473 has adhesive thickness 0,26 mm and 12'x12' costs 14,4 euro.

I will get some of the 9460 and experiment with it as planar membranes.
 
#18
I sorry all those part number got mixed up...... so confusing all this different VHB tape. well since they had good result with the cheaper 9460 🙂 instead of the more expensive 4910 i recon we go with the first.

about the conductivity, most of the people use graphite, or carbon. and the more expensive ones gold..... i gues that paint is carbon based. but the problem is, i dont know what the binder is an how flexible it is. since the VHB tape is double sides (at least the 4910 and 4905) you dont need a paint, put on the the carbon or gaphite with a brush and maybe push on it with paper towel or filt on a stick, or whatver to let it stick. when there is high voltage on the electrodes the piece of VHB sandwitched in between wil widen, if the electrode is not flexible (dried paint) there wont be any movement. this is the reason why some people use graphite or carbon grease, wich does not dry and stays flexible. i also recon stetch the menbrame as fas as you can , Then coat en let it shrink to the desired stretch ratio. this way you can build up a thicker layer of graphite or carbon black, and it also ensures when it stretched it still conducts.

i think we just need the VHB first before sinking money into paint or carbon. the cheap graphite might even work when the VHB is stretched coated and shrinked again.

graphene would ve awessome to for this application 🙁 but so hard to make or come by


By the way what would be the result of a verry thick carbon based grease , since you increase thickness resistance should go down. but because we dont use the EAP to vibrate itself but as a motor it really does not matter how much weight the electrode introduces. the menbrame does not have to go back and forth to produce sound, but more like sideways.



about the resistance question , its all in the pdf's i think they used a 10-100K Ohm menbrame so i dont even think its that critical. i wish i had money to spend this monh 🙂 for me buying from digi is like 2 times as expensive for a small amount
 
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