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.
* 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 amplifier board will amplify the signal then the analog to digital converter will digitize the signal and pass the data to the microcontroler board. The microcontroler board is based on the AVR Mega168 which will, further process the signals, and provide an interface to a computer.
*we are using the AVR Mega 168.
*The arduino software tools & GCC C tools and the AVR Mega 168 allows for a complete open source system...

== 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]]. Batch PCB from sparkfun.com worked well.

The 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.

== Status ==
*Editing the code of the Open EEG and Monolith EEG to be more portable and utilize avr-libc libraries more.
*Using the open Boarduno design to prototype the design.

== 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]]

== Description of How it Works ==

Neurons in the brain are not perfectly insulated -- some of their electrical activity leaks out and causes (very faint) electrical signals on the skin.

Dry skin is an excellent insulator, so "electrode gel" (typically skin lotion or shampoo) is used to help conduct the electrical signals to the electrode.
The researcher tapes the gel-coated electrodes to the skin, or uses a headband to press the electrodes through the hair against the skin.
Insulated wires attached to the electrodes bring the signals to the signal processing daughter board.

The signal processing daughter board is responsible for filtering and digitizing 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. 

On the signal processing daughter board is an anti-aliasing filter, an amplifier, and a [[Integrated_Circuits#ADC_analog_to_digital_converter | analog to digital converter]].
The instrumentation amplifier amplifies the differential analog signal on the input wires.
Then the signal is digitized by a a/d converter.
The a/d converter has approximately 20 bits accuracy so the signal does not have to be conditioned or filtered as much.

The "right leg driver" circuit on the daughter board is intended to decrease common mode signal.
That circuit inverts the common mode signal from the instrumentation amp, sums the result from each instrumentation amp, and sends the total back to the body.

The ADCs simultaneously digitize all the analog signals ''(really?)''.
The ADCs send bits of information (representing the original analog electrical signals) to the controller motherboard.

The controller board is the mother board of the system.
All the signal processing daughter boards plug into the mother board.
The controller board is based off the [[open hardware]] [[Arduino Links| Boarduino]] design.
The controller board includes a Atmel [[AVR]] Mega 168.
The controller board can be programmed using AVR GCC.

[[image:UCschematicardunonmonolith.png]]
Here is the circuit board of it.

[[image:PCEEG_Version_1.02_Alpha_05-09-08_uCBrd.png]]

Partlist

Exported from PCEEG_Version_1.02_Alpha_05-09-08_uC.sch at 6/16/2008 3:41:30 PM

EAGLE Version 5.0.0 Copyright (c) 1988-2008 CadSoft

Part     Value          Device          Package      Library      Sheet

B2                      RB1A            RB1A         rectifier    1
C0       1000uf         CPOL-USE5-13    E5-13        rcl          1
C1       .1uf           CAPNP-5@2       C-5@1        DISCRETE     1
C2       1µF            ELC-2,5         EL25B        DISCRETE@2   1
C3       330uf          CPOL-USE5-10.5  E5-10,5      rcl          1
C4       .1uf           CAPNP-5         C-5          DISCRETE     1
C5       47µF           ELC-5           EL25B        DISCRETE     1
C6       .1uf           CAPNP-5@2       C-5@1        DISCRETE     1
C7       .01uf          CAPNP-5         C-5          DISCRETE     1
C8       .1uf           CAPNP-5         C-5          DISCRETE     1
C9       47µF           ELC-5           EL25B        DISCRETE     1
C13      0.1uF          C-US025-025X050 C025-025X050 minimidi     1
C14      0.1uF          C-US025-025X050 C025-025X050 minimidi     1
D1       Green          LED3MM          LED3MM       minimidi     1
D2       RED            LED5            LED5         LED          1
IC1                     78XXS           78XXS        v-reg        1
IC2      ATMEGA168P     ATMEGA168PROUND DIL28/3      avr          1
IC105    TMV0505S       TMV0505         TMADCDC      MODEEG       1
J1       2.1MMJACK      2.1MMJACK       PJ-102A      minimidi     1
JP1                     PINHD-2X3       2X03         pinhead-ez   1
L1       22µH           L-10            R-12,5       DISCRETE@2   1
L2       22µH           L-10            R-12,5       DISCRETE@2   1
OK1      6N137          6N137           DIL08        optocoupler  1
OK2      6N137          6N137           DIL08        optocoupler  1
OK3      6N137          6N137           DIL08        optocoupler  1
R1       1k             R-US_0207/5V    0207/5V      rcl          1
R2       10k            R-US_0207/5V    0207/5V      rcl          1
R3       1k             R-US_0207/5V    0207/5V      rcl          1
R4       1k             R-US_0207/5V    0207/5V      rcl          1
R5       1k             R-US_0207/5V    0207/5V      rcl          1
R6       1k             R-US_0207/5V    0207/5V      rcl          1
R7       1k             R-US_0207/5V    0207/5V      rcl          1
R8       1k             R-US_0207/5V    0207/5V      rcl          1
R9       1k             R-US_0207/5V    0207/5V      rcl          1
S2       RESET          10-XX           B3F-10XX     switch-omron 1
SV1                     MA03-1          MA03-1       con-lstb     1
SV2                     MA09-1          MA09-1       con-lstb     1
SV3                     MA03-1          MA03-1       con-lstb     1
SV4                     MA03-1          MA03-1       con-lstb     1
SV7                     MA06-1          MA06-1       con-lstb     1
SV8                     MA08-1          MA08-1       con-lstb     1
USB.I/O                 MA06-1          MA06-1       con-lstb     1
X2       16.00MHz       CERMOSCILL      CERM_OSC     digg         1

Working on some other improvements... C123 with 1uF is much too small. Use 1000uF or so instead.

[[image:adschematicad1256devbrdnmonolith.png]]
Here is the circuit board of it.
[[image:PCEEG_Version_1.34_Alpha_06-15-08_ADBrd.png]]

Partlist

Exported from PCEEG_Version_1.34_Alpha_06-15-08_AD.brd at 6/16/2008 1:58:25 PM

EAGLE Version 5.0.0 Copyright (c) 1988-2008 CadSoft

Part     Value          Package  Library               Position (mil)        Orientation

C1       .01uf          C-5      DISCRETE              (3800 2950)           R90
C2       .1uf           C-5      DISCRETE              (3550 2950)           R90
C3       49uF           EL25B    DISCRETE              (3200 3000)           R270
C4       .01uf          C-5      DISCRETE              (3000 2750)           R90
C5       10µF           EL25B    DISCRETE              (2000 2850)           R270
C6       47µF           EL25B    DISCRETE@2            (1700 3000)           R270
C7       .01uf          C-5@1    DISCRETE              (1400 2950)           R270
C8       .01uf          C-5@1    DISCRETE              (1600 2700)           R90
C9       .1uf           C-5@1    DISCRETE              (1250 2750)           R90
C10      .1uf           C-5@1    DISCRETE              (1100 2950)           R90
C11      47uf .Tant.    EL25B    DISCRETE@3            (200 2450)            R270
C12      .1uf           C-5      DISCRETE              (200 1600)            R0
C13      47µF           EL25B    DISCRETE              (150 950)             R180
C14      .01uf          C-5      DISCRETE              (200 1250)            R0
C15      100pf          C-5      DISCRETE              (900 1950)            R270
C16      .1uf           C-5      DISCRETE              (700 1850)            R0
C17      47µF           EL25B    DISCRETE              (700 1650)            R180
C18      .1uf           C-5      DISCRETE              (1750 650)            R180
C19      18pf           C-5      DISCRETE              (2050 1550)           R180
C20      18pf           C-5      DISCRETE              (2050 900)            R180
C21      .1uf           C-5      DISCRETE              (3700 2050)           R90
C22      .1uf           C-5      DISCRETE              (2950 2050)           R270
C23      .001           C-5      DISCRETE              (200 2700)            R0
C24      .001           C-5      DISCRETE              (650 2500)            R180
D101     1N5818         D-10     DISCRETE              (2750 2800)           R90
IC3      5.0V-3.3V REG  78LXX    v-reg                 (350 700)             R90
IC201    TLC277P        DIL-08   BURR                  (700 2850)            R270
L3       22µH           R-12,5   DISCRETE@2            (3450 2700)           R0
Q1       7.68mhz        HC49U70  crystal               (2050 1200)           R90
R1       100            0204V    rcl                   (3000 3000)           R90
R2       470            0204V    rcl                   (2300 3000)           R90
R3       9.1k           0204V    rcl                   (2300 2800)           R90
R4       15k            0204V    rcl                   (2300 2600)           R90
R5       10k            0204V    rcl                   (1800 2750)           R90
R6       10k            0204V    rcl                   (1800 2550)           R90
R7       100            0204V    rcl                   (2200 550)            R180
R8       100            0204V    rcl                   (1200 400)            R90
R9       100            0204V    rcl                   (2500 2050)           R180
R10      100            0204V    rcl                   (2500 1850)           R180
R11      100            0204V    rcl                   (2500 1650)           R180
R12      100            0204V    rcl                   (2500 2250)           R180
R13      100            0204V    rcl                   (2500 1350)           R180
R14      100k           0204V    rcl                   (150 400)             R90
R15      100k           0204V    rcl                   (350 400)             R90
R16      100k           0204V    rcl                   (550 400)             R90
R17      100k           0204V    rcl                   (750 400)             R90
R18      49.9           0204V    rcl                   (600 1350)            R90
R19      49.9           0204V    rcl                   (850 1350)            R90
R20      200k           0204V    rcl                   (200 3000)            R180
SV1      AIN.0-7+AINCON MA10-1   con-lstb              (1700 100)            R0
SV2      AINCON. jump   MA03-2   con-lstb              (3650 900)            R180
SV3      D0-D3          MA04-1   con-lstb              (400 100)             R0
SV4      Digital.I/O    MA09-1   con-lstb              (2750 100)            R0
SV5      Vref+jump      MA04-2   con-lstb              (3300 600)            R180
SV6      Vref-jump      MA03-2   con-lstb              (2700 600)            R180
SV7      V.REF          MA03-1   con-lstb              (3550 100)            R0
SV8      DRL.I/O        MA04-1   con-lstb              (900 100)             R0
SV10     High Z.jump    MA03-1   con-lstb              (3350 2350)           R0
U$1      ADS1256        DIL28-6  brog-ads1256_#7_      (1500 1500)           R270
U$2      CD40109BE      DIL16    brog-cd40109be_#Done_ (3350 1600)           R0
ZD       4V             TO92-CLP v-reg                 (2500 2850)           R270

== 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

==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.


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.

== 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. It will amplify the signal less requiring less analog signal processing and use the more sensitive a/d converter to make up for less amplification and cause less signal attenuation.

* $12.00 The ads1255 or ads1256 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 can be soldered by a hotplate or hot air rework tool.

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

==Electrical Isolation From the PC. ==
This isolates the PCEEG from the computer when used with a DC to DC converter.

=== DC to DC converter ===
The design is based on the modular eeg and monolith eeg they use a TMV0505S, but it is not available in many places. It will be replaced with NMV0505SA. This converter has a rather high output voltage (6-7 V) at very light loads.
Therefore, when building the digital board measure the voltage in the +5V/3 of modular eeg designnet, e.g. at IC103 pin 8.

The voltage should be LESS than 6V. If not, you must reduce the value of R127 (near the LED), in order to present the DCDC converter with a higher load.

=== Optocoupler ===
A optocoupler by Fairchild 6N137 is used to transfer data from the microprossesor to the Rs232 converter by light.

"The MonolithEEG uses 6N137 opto-couplers which can reliably transmit data at rates above 1MBaud. This provides a simple way to higher sampling rates for the MonolithEEG"

"The ModularEEG allows the replacement of the 6N139 with the faster 6N137. Soley the resistors R125 and R130 on the digital board have to be taken out otherwise both receivers would be disabled permanently."

== Software Tools ==
* EAGLE CAD is being used to create the first PCB. surface mount is used to save space.
*[[gEDA | gEDA tools]] may be a option for opening this design to a wider audience.
* Maxima a computer algebra system s used for graphing and math displays.
*SPI interface code for a/d converters from TI for developers

=== How You Can Help ===
#. get the tools

== 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) )''

== ideas for future work ==

Currently most EEGs (and EKGs) have "passive electrodes" -- it's a conductive button pressed against the skin, with a long wire that takes the faint signal to the amplifier in the box.

A few EEGs have [http://openeeg.sourceforge.net/doc/hw/ae.html "active electrodes"] -- the amplifier is on top of the conductive button, and sends a strong analog signal down the long wire to the ADC in the box.

[[User:DavidCary]] is thinking about going one step further:
put the amplifier and the ADC on the electrode, sending out digital packets to the box.
Can I do all that with a single chip -- an 8-pin PSoC?
Also, instead of each electrode having its own dedicated wire to the data collection box, all the PSoCs are connected in a string (or some other network), forwarding packets from one to the next, so no matter how many electrodes are connected, only about 4 wires (2 power + 2 digital data) are connected.
I haven't decided yet whether it's better to have every node do both -- sample data and forward packets -- or if I should split them up, with PSoCs sampling data and sending it to a hub, and hubs (perhaps not PSoCs) forwarding data from a few local PSoCs and from other hubs.
--[[User:DavidCary|DavidCary]] 08:50, 10 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.


== See also: ==
* [https://electrical.codidact.com/posts/287954 "what can you do to mitigate noise pickup... [in] ... EKGs...?"]
* [https://electrical.codidact.com/posts/288010 "What is a good PCB-layout? ... an ECG-amplifier circuit."]
* [http://www.nytimes.com/2008/01/15/science/15robo.html?ex=1359090000&en=69146e0fb3807a74&ei=5124&partner=permalink&exprod=permalink/ Monkey’s Thoughts Propel Robot, a Step That May Help Humans ]
* [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]?
* [http://www.makezine.com/blog/archive/2006/01/homemade_electrocardiograph.html Make: Homemade Electrocardiograph] ([http://www.eng.utah.edu/~jnguyen/ecg/ecg_index.html] recommends skin lotion or shampoo as a low-cost electrode gel)




[[Category:Projects]]