Hello,
I am relatively new at circuits, but a few friends of mine we want to, sometime in the future, work on an EEG. I have read that there is a danger of having out-of control voltage and essentially shocking the user of the EEG through his brain which is, obviously, very bad.
A solution that came to mind is to not actually have a reference voltage on the head, but rather some insulating blob of material somewhere on a distant circuit. This would mean that the actual voltage signal might have a huge DC offset relative to its approximately 3 microvolt amplitude. (Correct me if I'm wrong). Thus, if we were to feed this through a differentiator, it would give us a nice signal centered around 0V so that it can be amplified without producing monstrous voltage values.
(The graph on this wiki article is an example of what we are going for http://en.wikipedia.org/wiki/Event-related_potential)
My main issue however, is that the signal we are going for is a low frequency signal, whereas the noise is potentially a high frequency noise, so differentiating it would be a terrible idea. Thus, I want to know, is there a way of feeding a signal through a differentiator while having something act as a low-pass filter?
Also, would taking a constant but external reference voltage help at all in the issue at hand, that is, the risk of shock?
Also, do you have any other ideas of how to counter the problem of taking a low-amplitude low-frequency signal with an arbitrary DC offset?
Also, would it be possible to have the electrode itself modulate to something like a flashing LED, and connect that via some sort of fiber optics to a photodiode and pick up the signal from there?
Thanks in advance
The project is currently at its initial stages, and any radical changes to the methodology are welcome
---
Edit:
I intend to use an arduino board to somehow read the final signal. I have yet to purchase one and start fiddling with it, so I am not too sure how that is going to work.
I am relatively new at circuits, but a few friends of mine we want to, sometime in the future, work on an EEG. I have read that there is a danger of having out-of control voltage and essentially shocking the user of the EEG through his brain which is, obviously, very bad.
A solution that came to mind is to not actually have a reference voltage on the head, but rather some insulating blob of material somewhere on a distant circuit. This would mean that the actual voltage signal might have a huge DC offset relative to its approximately 3 microvolt amplitude. (Correct me if I'm wrong). Thus, if we were to feed this through a differentiator, it would give us a nice signal centered around 0V so that it can be amplified without producing monstrous voltage values.
(The graph on this wiki article is an example of what we are going for http://en.wikipedia.org/wiki/Event-related_potential)
My main issue however, is that the signal we are going for is a low frequency signal, whereas the noise is potentially a high frequency noise, so differentiating it would be a terrible idea. Thus, I want to know, is there a way of feeding a signal through a differentiator while having something act as a low-pass filter?
Also, would taking a constant but external reference voltage help at all in the issue at hand, that is, the risk of shock?
Also, do you have any other ideas of how to counter the problem of taking a low-amplitude low-frequency signal with an arbitrary DC offset?
Also, would it be possible to have the electrode itself modulate to something like a flashing LED, and connect that via some sort of fiber optics to a photodiode and pick up the signal from there?
Thanks in advance
The project is currently at its initial stages, and any radical changes to the methodology are welcome
---
Edit:
I intend to use an arduino board to somehow read the final signal. I have yet to purchase one and start fiddling with it, so I am not too sure how that is going to work.
Last edited: