Programmable Chip EEG

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Revision as of 00:08, 13 November 2006 by DavidCary (talk | contribs) (A/D converters)
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The Programmable Chip EEG

Welcome to the PCEEG Wiki, where everyone can add to this EEG brain-computer interface!

Here is a diagram of how the analog signal processing boards and the microprocessor board will come together. Pceeg.jpg

What it is and what it can be used for

The Programmable Chip EEG is a Modular Multi-channel electroencephalograph that could be used for a brain-computer interface, biofeedback....

The Programmable Chip EEG is programmable because it uses Digitally Programmable Potentiometers. They are used to set the Gain, frequency range, and can calibrate multiple analog boards for different EEG tests.

Status

We currently have a (preliminary?) circuit design and a (prelimary) PCB layout. Eventually, kits could be sold, if there were interest. More info is available at the PCEEG SourceForge home page at PCEEG sourceforge.net.


How You Can Help

  • I2C interface diagram for programmable resistors and a/d converters 12 or more bits with low cost.
  • SPI interface diagram for programmable resistors and a/d converters 12 or more bits with low cost.
  • linear switcher cad schematic drawing from PCEEG technology applied to the Open EEG design with improvements.
  • migrate from switcher cad to pcb express.
  • migrate from pcb express to eagle cad after testing to further development.

News

The design is switching to EAGLE CAD, because the auto-router is excellent for open-source productivity. It will allow the design to evolve faster and with less work with a wider selection of PCB production houses to choose from.

Here is a picture of the PCEEG being done in EagleCAD. Eagle sample.GIF The eagle cad file is here Media:PCEEGHD.zip

The ideas and monkey to robot arm interface by Miguel Nicolelisis very inspiring. He used implanted electrodes to monitor and allow monkeys to control a robot arm as if it was their own. Could the PCEEG do the same with its electrodes on the scalp. Only the future will show.

Description of How it Works

The daughter signal prossesing board is responcible for filtering and digitising the signals from the body, then the signals are passed to the control board that is the motherboard. The motherboard then can pass the signal to a larger computer.

The differential analog signal is amplified by the instramentation amplifier. Then the signal is amplified and conditioned by high pass and low pass filters.

The common mode signal is inverted summed and sent back to the body to decrese common mode signal thsi is done by the driver right leg circuit.

Band reject filters may be added soon in the future.

Then the analog signals are simultaniously digitized and the digital values can be clocked to the controler motherboard.

The controler board that is the mother board of the system and the signal prossesing daughter boards plug into is the AVR Butterfly

Parts used in the PCEEG:

To reduce noise in the readout of the analog part of this circuit, a common-mode feedback is passed back into the body by the driver right leg circuit. Band reject filter may also be used (to reject, for example, 60Hz noise from nearby A/C power wiring).

The analog signal prossesing board will digitise the signal and pass the data to the control board. The control board is based on the AVR Butterfly which will, further process the signals, and provide an interface to a computer & lcd display.

Open Source Circuit Design

Open source (public) results!

PHP will be used to create a database of users and what they sample and choose to share with the open source community.

The database will give statistical analysis on users recordings.

Also the extension of SETI called BIONIC could be used as a distributed library creation of artifacts and data mining.

Please contribute and make the PCEEG a great tool for researching brain computer interfaces.

A/D Converters

The programmable chip EEG needs an A/D converter to convert the analog signal (at the output of the instrumentation amplifier) into digital bits. We expect this project to require at least 12 bit ADC.

Many Atmel and other microcontrollers have a built-in ADC, but those are at most 10 bit ADC, so that ADC is useless to us -- we are forced to use an external ADC.

What low-cost ADC are available with at least 12 bits?

  • $2.50 MCP3301 has 1 ADC input (13 bits)
  • $3.50 MCP3302 has 2 ADC input (13 bits)
  • $3.50 MCP3204 has 4 ADC input (12 bits)
  • $4 MCP3208 has 8 ADC input (12 bits)
  • $8 dsPIC30F microcontroller has 8 ADC inputs (12 bits).

See also: