Detailed Signal Format (from Dr T. Collins)

The 16 bit sample values are stored as unsigned integers with a range from 0 to 1023.

A zero volt signal is sampled as 512.

As 1023 is the maximum, the six most significant bits are never used and so are always zero.


High Byte Low Byte
000000XX XXXXXXXX
MSB

Where X= 1/0

The EEG digital board samples at a rate of 256 samples per second so a frame of samples is transmitted every 1/256 seconds.

As there are 17 bytes in each frame packet this means that 256x17 = 4352 bytes are transmitted every second.

size of metal box

http://www.maplin.co.uk/module.aspx?moduleno=43713

Metal box with size 120x95x30 from Maplin is suitable for analgoue board.

Tips for using budgets

Hi everyone,

Today Jack and I had a go of buying items using budgets in the serving window in the building of material and metallurgy. And the process is simple.

Just go there and tell the guy that you want to use final year project budgets to buy some items and then you'll get a white-paper form to fill in. You'll need to know your project number and there is a category there in which you can find out.

Today we've got a PP3 battery but we haven't searched the boxes yet because we're not sure about the exact size of box we need. So I'm not quite sure whether we can get the boxes there. But there's lots of items and hopefully we can find the boxes. Just go there and search the index. Looking forward to your good news!

Victor

ElectricGuru Screenshots

We had a go at using ElectricGuru on the lab PCs with a modular EEG board wired up with the calibration signal to channel 1 and channel 2 shorted to ground. The .exe file runs fine although for some reason the time-domain plot didn't work for us. To try it out, download from http://www.realization.org/page/topics/electric_guru.htm and set the Machine under the preferences menu to RS232EEG

OpenEEG Software

1.Electric Guru : It is a very simple but powerful application that is good for troubleshooting and checking that your electrodes are reading valid signals.
Electric Guru includes the signal plotted in the time domain along with frequency response and phase differences.

ABI BCI : Is a small windows application that implements a neural network for biofeedback training.It works by taking a raw EEG signal and filtering it down to frequencies that you specify.It then sends those specific filtered signals into two layer feed-forward neural network that learn how to differentiate between two or more different types of signals.

BioEra:
One of the best program that interact with openEEG. It allows the user to build designs out of a large list of components. BioEra also provides the user with enormous control of each component.

Expected Features of an Awake EEG

Dear All,

Please find a link describing the common features of a normal awake EEG

http://emedicine.medscape.com/article/1140143-overview

Also describes locations where the particular waveforms are best found which is useful since we are only using a few channels and need to concentrate them in the correct area.

Steve

OpenEEG screenshots

Hi all

We had a go at hooking up an OpenEEG board to some electrodes and got some measurements. The screengrabs are all of a 0.5 second time-frame:

1. Lots of activity on channel 2 - so much that it is clipping

2. Typical Output. Some mains hum visible (50Hz = 25 cycles in this 1/2 second time-frame)

3. This is without the right-leg driver ear-clip connected. Lots of mains hum!

4. Some very clear eeg activity on channel 2 (approx 9Hz)

Neural Wheelchair Control

http://www.youtube.com/watch?v=0at3NzNRySg

Cables and connectors

I am purchasing 3 off of the following to test out ..
1m audio cable with a jack on one end and bare on the other
Jack Socket

Farnell details:
Code Qty Description
1219360 3 LEAD, 3.5MM S JACK-BARE END,1M PRO SIGNAL-AUDL-73-1M £5.76
1267374 3 SOCKET, 3.5MM JACK, 3POLE MULTICOMP - MJ-074N £2.13

For enclosures there are amny to choose from - though some seem expensive for what they are:
Enclosures from RS
Enclosures from Farnell
Our boards are 100mmx800mm BUT we need to be sure they fit INSIDE the box and that there is room for any screws/connectors so 1 or 2 cm spare could be useful.
This board is 120x120mm
(I would prefer a painted version of the same dimensions. The flanges may be handy for fixing inside the surrounding box).

Electrode Placement

Enclosures for our boards

We will need to place our analgoue board in a metal box. This can then be placed with the digital board in a plastic box. (See Nelo's picture below. Note the analgue board is boxed at the bottom).

Boxing is mentioned in the modular OpenEEG FAQ
http://openeeg.sourceforge.net/doc/faq.html
"Q: Why is putting both boards in the same metal box a safety issue?
A: It is because you need to let the power and output signals pass through the box wall somewhere. There you have to ensure that the connectors are isolated from the box, or you will end up connecting isolated ground to PC ground, which is a bad thing. Even if the connector housings are made of plastic, you risk lowering the isolation voltage.

It is possible to use a metal box, if you create wide enough gaps between the connectors and the metal wall. Problem is, you still end up with an outer surface connected to isolated ground, so it is safer to avoid the subject entirely.

It is recommended that you put the amplifier board in a metal box, which is in turn placed in a plastic box along with the digital board. Look here for an example."