Electrodes attached to metal bars or other object?

Cables, Electrodes, Plugs, etc.
sef
Posts: 2
Joined: Wed May 27, 2015 8:00 am

Electrodes attached to metal bars or other object?

Postby sef » Wed May 27, 2015 8:32 am

Hi,

Short introduction:
I'm currently developing a interactive installation in a dome with Kinect and Bitalino. Idea is that visuals+sounds will adapt according to your ECG and body movement. It will be used by one person at a time for about 5 minutes. During a day many people will use it.

My question:
Is there an alternative to attaching the electrodes on the body? Because attaching the electrodes to every person will take a lot of time. Is is possible to attach the electrodes to a metal part for instance and let people hold this? Like they do in this movie for instance:
https://www.youtube.com/watch?v=hQ3BUBV-BBM
That way we could quickly switch between people. Accuracy is not very important in this installation, as long as I have some kind of heart rate signal.

Any help or advice would be greatly appreciated. I don't know so much about electrodes and how to use them yet. The way I understand it the main purpose of the electrodes is to reduce noise of the incoming signal, right? Just touching a metal wire would generate too much noise?

Kind regards,
Sefrijn

BITalino
Site Admin
Posts: 567
Joined: Tue Aug 27, 2013 3:47 pm

Re: Electrodes attached to metal bars or other object?

Postby BITalino » Wed May 27, 2015 8:51 am

Hi Sefrijn,

Looks like an awesome project you're working on... we'd love to hear about how it works out and also to help spread the word once it's ready ;)

Regarding the electrodes you can certainly use other materials. Non-gelled reusable electrodes such as the ones on the link below are an option that's easy to integrate in objects:
http://store.bitalino.com/index.php/standard-account-store#!/Non-Gelled-Reusable-Electrodes/p/35652024/category=9071126

In the particular case of the bicycle handlebars we've used conductive lycras, which work well also:
http://store.bitalino.com/index.php/standard-account-store#!/Conductive-Lycra-Fabric-Electrodes/p/35652031/category=9071126

Other alternatives include stainless steel (even attaching a disposable electrode to such a surface should provide a minimum viable signal), and removing the conductive gel and plastic rim from the disposable electrodes (leaving only the Ag/AgCl core, which can be reused).

We hope you found this information useful. Do let us know in case you have any further questions.

Best regards,
The BITalino Team

sef
Posts: 2
Joined: Wed May 27, 2015 8:00 am

Re: Electrodes attached to metal bars or other object?

Postby sef » Wed May 27, 2015 3:07 pm

Thank you for the quick reply and your enthusiasm. I'm looking forward to integrate the Bitalino into the project.

So if I understand it correctly the main purpose of the electrodes is that they stick to your skin and conduct electricity, but it could be any conductive material attached to the sensor? I mean, there is no special material required to sense electrical currents on the skin? Sorry, I really don't know so much yet about biofeedback, the chemical process and measuring body signals.

I spend some time trying to understand the process by reading this article. Maybe it is also helpful to others:
http://www.mdtmag.com/articles/2011/08/ ... technology

So from what I read here there is some kind of chemical process going on with the skin and the gel?
But after reading your message I understand it is also possible to remove the gel and plastic and reuse the disposable electrodes, or buy these:
http://store.bitalino.com/index.php/sta ... ry=9071126
So I imagine the reusable non-gelled electrodes are made of a different type of material?

If you know about any other resources to clarify this process and the sensing possibilities I would also be very grateful.
I hope I don't ask too many questions, but it helps me to understand what is going on during the measurement process, so I know what variations are possible and why.

BITalino
Site Admin
Posts: 567
Joined: Tue Aug 27, 2013 3:47 pm

Re: Electrodes attached to metal bars or other object?

Postby BITalino » Wed May 27, 2015 7:53 pm

Hi Sefrijn,

Feel free to post as many questions as you'd like; we'll do our best to support. Apologies for not including all the relevant details in the previous reply... indeed as your research revealed, the electrode material is extremely important.

If you're looking for top-of-the-line signal quality, there's nothing like pre-gelled electrodes. The thing is that for many everyday applications one can relax such requirements at the expense of having to deal with increased noise, but with the advantage of dramatically improving the user experience.

This being said, one of the purposes of the electrodes is indeed to stick the electrodes to your skin (the white foam rim on the electrodes bundled with BITalino); the purpose of the conductive gel is to provide better electrical conduction (the blue gooey stuff on the middle).

But, the core of the electrode (dark grey disc to which the stud is attached) is the same material used in the reusable non-gelled electrodes (Ag/AgCl). In the electrodes bundled with BITalino it only has the gel to improved electrical conduction (which the non-gelled do not).

Even the conductive lycras are fabric embedded in Ag/AgCl. Nevertheless, there are other metals with close-enough properties that make them suitable electrodes... stainless steel is one such material; if time allows you, a cool thing is to experiment with a few materials and see which work for you.

Another useful piece of advise for your project is to consider / experiment not only with the ECG sensor, but also with the EMG sensor as well (using the same electrode placement as in the ECG).

In some cases it provides a better performance given that the filter on the EMG gives you a virtually flat line with a bump whenever the heart beats. That was the sensor we used for example in these projects:
https://www.youtube.com/watch?v=BeOBV-46VQo
https://www.youtube.com/watch?v=nV68hZDTFyg

Hope you found this information useful. If you'd like us to send a few pictures with options on how to connect metals to your BITalino sensors just let us know.

Best regards,
The BITalino Team


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