Editing Programmable Chip EEG

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

== PCEEG, What it is and why it can be the best ==
* The [http://pceeg.sourceforge.net The Programmable Chip EEG] gets its name because its hardware and software can be adjusted digitally from a home pc. 
* [http://pceeg.sourceforge.net The Programmable Chip EEG] is a Modular Multi-channel electroencephalograph.
* This can be used for a brain-computer interface with biofeedback using a flex sensor or servo to detect fingure movements. 
* The [http://opencircuits.com/LT1168 LT1168 Programmable-Gain Precision Instrumentation Amplifier] is used to amplify the weak electric signals coming from the brain through electrodes attached to the scalp, and has internal protection circuitry for the user.
* Several matched [http://opencircuits.com/LT1114 LT1114 Low Power Precision OP-Amps] are used for amplification and filtering of the signals.
* ESD Protection in [http://opencircuits.com/LT1168 LT1168 Programmable-Gain Precision Instrumentation Amplifier] Chips have been chosen that fallow the human body model of esd protection this can be seen in the 1168  datasheet.
* 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, 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 PIC18 which will, further process the signals, and provide an interface to a computer.
(We considered using the Atmel AVR, but we chose the PIC18 because ... [FIXME] ...).

== Status ==
We currently have a (preliminary?) [[circuit design]] and a (prelimary) [[PCB layout]].  
We are using EAGLE CAD to draw the scematic.

== Hardware Overview ==
Here is a diagram of how the analog signal processing boards and the microprocessor board will come together.
[[Image:Pceeg.jpg]]
Here is how the analog signal prossesing board will come together.
[[Image:newpceeghddesign.png]]

Great cows basic and a 18 series pic would work well and be quick to implement. Also that allows for a complete open source system...

==ESD Protection in 1168==
Chips have been chosen that fallow the human body model of esd protection this can be seen in the 1168  datasheet.

== 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 digitised by a analog to digital converter. The a/d converter has aproxamitly 20 bits acuracy so the signal does not have to be conditioned or filtered as much.

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.

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 PIC18 useing great cows basic.
=== How You Can Help ===
#. get the tools

== Software Tools ==
* We are using LT switcher CAD to draw the scematic. This also is a SPICE Simulator used to analize the amplifier design.
* EAGLE CAD is being used to create the first PCB. surface mount is used to save space.
* Maxima a computer algebra system s used for graphing and math displays.
*SPI interface for a/d converters
*linear switcher cad schematic drawing from PCEEG technology applied to the Open EEG design with improvements.
*[[gEDA | gEDA tools]] may be a option for opening this design to a wider audience.

== Parts used in the PCEEG: ==
* [http://opencircuits.com/LT1168 LT1168 Resistor-Programmable-Gain Precision Instrumentation Amplifier] is used to amplify the weak electric signals coming from the brain through electrodes attached to the scalp, etc.
* Several [http://opencircuits.com/LT1114 LT1114 Low Power Precision OP-Amps] are used for amplification and filtering of the signal

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 UBW which will, further process the signals, and provide an interface to a computer & lcd display.

== News == 
The design is switching from LT switcher CAD (aka [http://www.nuhorizons.com/xpresstrack/ltcswitcher/ LTspice SwitcherCAD]) 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 Manufacturers]]. 

Here is a picture of the PCEEG being done in [http://www.cadsoft.de/freeware.htm EagleCAD].
[[Image:Eagle_sample.GIF]]
The eagle cad file is here [[Media:PCEEGHD.zip]]

The ideas and monkey to robot arm interface by [http://www.answers.com/topic/miguel-nicolelis Miguel Nicolelis]is 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.

== Open Source Circuit Design ==
* [http://opencircuits.com/Programmable_Chip_EEG Open Source Circuit Design ]
* [http://pceegbci.blog.com/ The Programmable Chip EEG Open Source Circuit Design BLog] ''(BrokenLink -- I hope this is only temporarily offline. --[[User:DavidCary|DavidCary]] 10:12, 8 October 2007 (PDT) )''

== 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 20 bit ADC.

''(In 2007-02, some one claimed "We expect this project to require at least 20 bit ADC." -- why? Many people (*) do EKGs with only 10 bit converters.)''


* $12.00 The ads1255 by ti is a great a2d converter it has programmable gain and digital low pass filtering with 24 bits of resolution 30KSPS. It is a 20-SSOP so it might be able to be soldered by a hotplate or hot air rework tool.

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.

The newest system is a dc amplifier without a high-pass, and all the low-pass filtering is digital

== The Goal ==
Eventually, kits could be sold, if there were interest.
More info is available at the PCEEG SourceForge home page at [http://pceeg.sourceforge.net/ PCEEG sourceforge.net].

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== See also: ==
* [http://wiki.asiaquake.org/openeeg/published/ The OpenEEG wiki]
* [http://pceegbci.blog.com/ The Open EEG Brain Computer Interface BLog]
* [http://www.larryheadinstitute.com/eeg-training.html EEG Training Seminars]
* [http://pceeg.wikia.com/wiki/Main_Page wiki cities on pceeg]
* [http://pceeg.sourceforge.net pceeg.sourceforge.net]
* [http://www.answers.com/topic/miguel-nicolelis miguel nicolelis]
* [http://maxima.sourceforge.net/ Maxima - a computer algebra system]
* [http://www.scienceprog.com/ digital high pass filters and other circuits]
* [http://hcvl.hci.iastate.edu/cgi-bin/openEyes.cgi human and computer vision lab]
* [[PCB Manufacturers]] such as [http://www.batchpcb.com/index.php www.batchpcb.com]
* [http://vulliard.dyndns.org/~vulliard/ eeg biofeedback "mind machine"]
* [http://freenet-homepage.de/moosec/projekte/simpleeeg/index-Dateien/Page431.htm monolith eeg]
* [http://mindhacks.com/blog/2007/01/meg_scanning_the_bra.html yet another pundit disrespects the EEG]
* [http://www.pololu.com/laser_cutting.html lazer cutting for box & solder paste stencil]
* [http://www.amazon.com/Build-Your-Printed-Circuit-Board/dp/007142783X?tag2=zottmann1-20 Build Your Own Printed Circuit Board]
* [http://www.stencilsunlimited.com/solder_products.php solder paste for surface mount that can be stored at room temperature]
* The thread [http://forum.microchip.com/tm.aspx?m=114626 "amplifying biomedical signals: 150 uA with 16 bit resolution?"] has several op-amp suggestions, and mentions that "a good, low-noise, low-cost, isolated EMG/EEG amplifier is one of the most demanding analog electronics designs."
* [http://www.e-dsp.com/how-to-build-your-own-heart-monitoring-device-a-simple-ecg/ How to build your own ECG device]
* [http://www.alertfocus.com/evidence/music17.php neurofeedback helps musicians improve their musical performances by 13 to 17 per cent.]
* [http://health.groups.yahoo.com/group/biofeedback/ "the World's largest Biofeedback and Neurofeedback Discussion Group"]
* TI app note [http://focus.ti.com/docs/solution/folders/print/272.html "Biophysical Monitoring: Electrocardiogram (ECG) Front End"] has a simple circuit: 390 KOhm resistors in-line with each lead -- one end touches patient, the other end directly connected to the instrumentation amp input (or the right-leg drive amplifier output, which has no further protection). The inst. amp has 2 protection diodes on each input, directly to +power and -power. Also, 39 pF capacitor from each input to analog GND, and 200 pF between the 2 inputs. The TI publication "Information for Medical Applications" (2Q 2004) reprints that circuit, but leaves out the caps and the diodes.
* (*) [http://www.ieeta.pt/~escadas/ucecg/applications.htm Some people use 420 Hz sampling rate, 10 bits/sample.]
* [http://bsamig.uku.fi/pdf/QRSdet.pdf "High-Resolution QRS Detection Algorithm for Sparsely Sampled ECG Recordings"] by Timo Bragge et. al. 2004 recommends: "the sampling frequency of the ECG should be at least 500 Hz"
* [http://www.analog.com/library/analogDialogue/archives/29-3/low_power.html "Low-Power, Low-Voltage IC Choices for ECG System Requirements"] by Jon Firth and Paul Errico says "The multiplexed architecture, based on an old assumption that the converter is by far the most-expensive front-end component, is prevalent in today's electrophysiological measurement systems. However, with the proliferation of sigma-delta converter architectures, converter-per-channel is now a power- and cost-competitive alternative". It also gives a typical schematic for both architectures and suggests some parts.
* Is there a [http://www.electronicproducts.com/ShowPage1.asp?SECTION=&PRIMID=&FileName=medtelconf3%2Ejul2004%2Ehtml&ReturnLink=%2FSearch1%2Easp%3FManufacturer%3D%26Keyword%3Dimplantables%26Slot%3D0%26StartNum%3D1%26stype%3D%26year%3D10&MonthYear=Jul+2004 Medical Electronics Forum]?




[[Category:Projects]]