Indesman

Indesman

Indesman

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2009 Fixed EEG helmet concept for dry/wet electrodes

This is one of the most exciting projects  I have ever done.  The interesting part of this project is many fold  and requires a lot of insight  of human  skulls  and pressure  applied to the skin to make the physical connection,  and how to make a model that  can be modified  easily  for different applications and manufactured.  Then comes all the issues around the electronics  and making sure to pick up the signals correctly, but I won’t talk about that here.

One of the major interesting things in doing this project was to figure out how to apply at 10/20 system  in a solid model that was stiff helmet type that would fit a lot of different people.

One of the first things I did was I  it try to understand  where to go from on the head  so you would think the most people in one design.  One thing I realized when I designed the system, was  that if you want to fit a 10/20 system precisely, the points where you measure you will move, depending on the head size. You see this if you were blow up a balloon, and you mark a point on it, and blow it more up you see it moves. And if you look at the nature of the 10/20 system and vectors and angels, it result that the sphere and vector point crosses each other in different distance from the centre top point. (I hope it makes sense 🙂

Here are some of the pictures from the process of creating the element.

After two weeks of  hard work  it looked like this…

but my major question was how do I make  each arm fit the head  precisely.  so back to drawing board I have to work on a  more clever solution.

Second phase:

after a week off looking at this design I to build it in a different  way,  using  wires,  so  I measured up ahead according to  the 10/20 system.  and after three days look like this.  not a pretty sight but it gave me a very good idea of how the final one should look like.

now I really started to understand how the whole thing should be built in a very simple way.  and yet be very flexible and easy to reproduce in many samples.

so after a week  it looked like this.

now things start to move fast,  and I was able to make a new  design that looked cool and was easy to do.

here is how that looked,  after  bending it and man was that a good feeling when I put it on the first time.

the sensor head  suspension,  was made to fit any kind of hit no matter how  it looked at a given point.  so to be able to make it super  flexible in all directions, I decided to make it in  silicone where the  thickness of the  curved arms   would decide how  hard it would press against the head.  the first  sensor  head suspension looked like this.

It was now time to make the final  concept design of the helmet and put it together.

the sensors would look like this;

and

Here’s the final exploded electrode where you can see the little joystick  for   getting the pins through the hair,  and the  Orange suspension is made to push the sensor head into the hit no matter the angle  to the head scalp.

the final assembly looks like this  before bending,  kind of interesting I think still.



So now I just had to make it for real, and here we go….



and here is an electrode head…


and wired up… almost done 🙂

and after bending finishing it…

it looked like this:


and

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comments

wow… that is an excellent design… well done. just brilliant.

irfan

August 31, 2011

Thanks, I appreciate that.

jakobolrik

August 31, 2011

Hey this is really cool… how did you get the dry electrode to conduct without an electrolyte? just pressure? I like your development process, nice work.

Jordan

December 17, 2011

Well there are many factors that means a lot. Material, Shape, Pressure and Filters, Electronics. I’m not sure that i’m 100% right in what I write, but this is my observations and my experience.

What I learned was that a single pin, with a round head, AgCl 8mm electrode is fine. Very light pressure e.g. 100-150g(higher pressure = pain :-). When you work with Dry electrodes, the DC offset tells you how well you are connected to the skin. So you need to be able to handle the DC offset when you sample. important is that you eleminate the DC to get a better resolution. if you don’t your electrode will saturate. So your electronics has to be able to handle many different DC/offsets from each electrode, and eliminate it.

You have to reference to the ear lopes or behind the ear. And make sure you have a good connection there. Every electrode is separated from each other.if this changes, everything gets a big mess.

Then I would use a AgCl electrode. You will always have problems movement as you might know. So depending on what you are looking for you have to consider this in your signal processing.

Well I can talk for hours, about this since it’s very interesting.

I would love to see some designs you do, if you ever get that far.

jakobolrik

January 31, 2012

Hey, I am interested in finding out how you made the sensors or where you bought them from. We are building a portable eeg monitor for a senior design project and we are having trouble finding dry pin electrodes..we want to find electrodes that would give us better signals. Can you please reply and let me know..Thanks 🙂

Mia

January 31, 2012

Well, two things. First I have seen it solved with AgCl electrodes. And the boys that did it was very clever and good in this.
So it can be done. As I wrote in an other post, a single pin 8mm round head pin, should do the job. So a pure silver pin, with a AgCl surface should be what you are looking for.
It takes some time for it to settle, and for the DC offset to go away on all pins, so don’t expect fine results the first 2-5 min.

May I ask where you work or study?

jakobolrik

January 31, 2012

Hey thanks for the reply..can you please give me your email id?

Mia

January 31, 2012

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