From: Mr Tim Nelson (wayland76_at_yahoo.com)
Date: 2002-06-07 12:21:41
Would've been more useful if I'd attached the file,
wouldn't it. Hopefully this will have it attached
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Editor: Tim Nelson <wayland76@MYNOSE.yahoo.com>
Yes, remove my nose to e-mail me. I do not wish to receive any commercial e-mail.
When it says "Author", it's the answerer. "Date" is the most recent update
More info? We have a wide range of sources. For general project information, and questions about EEG, biofeedback, and the like, try the Basics section of the OpenEEG site. Another important link is the Main OpenEEG site site. If you're looking for code, and the tracking system, and the like, you'll need our Sourceforge site. Or, there's the Mailing list.
A FAQ! (I have been nagging about this before... Please, anyone, HELP!)
[Ed. note: ask, and you shall receive]
Well, there are [four] projects. Two that I work on, and one that Joerg Hansmann and Mortiz v Buttlar work on [and one by Joerg Hansmann].
| Project | Project leaders | Last estimated parts cost | Why? |
|---|---|---|---|
| ModularEEG | Joerg Hansmann and Mortiz v Buttlar | [From the old FAQ] breaks the EEG into modules. This allows up to 6 channel operation. There are still some problems with the analog section. | |
| RS232-EEG | Joerg Hansmann | Original? | |
| TinyEEG | Andreas | "A couple of hundred" | To make a very small, surface mount EEG device |
| "Cheap, beginner project" | Andreas | $70 ($50 in bulk) | An attempt to bring EEG even closer to the masses |
All three projects have these parts in common: They will all have an analog section and a digital section, and a power-system.
The analog section consists of a sensitive input amplifier and an anti-aliasing filter.
The digital section consists of an AD-converter, a microcontroller and an optical link to a serial port.
I can't speak Joerg's and Moritz's 'ModularEEG', but my hardware is not finished. The digital section works great, but the amplifiers and power system need to be reworked.
a-b: Yes
c-d: It depends. The bandwidth is 10kbyte/s. What you do with it is up to you - the microcontroller is easy to program.
[Ed. Note: Andreas, what's the a-b, c-d business?]
A previously set goal was to be able to interface with any hardware on the market. A minimal specification is a 2-channel EEG device that communicates over the serial port.
Yes, but since it is more complex and expensive to use, it might be better to begin with serial port and add USB later. This is a sub- project someone with knowledge in digital electronics could work on. Volunteers?
It has been discussed. A lot of boards have a 20Hz highpass filter that removes the very signals we are interested in. On modern sound- cards, this is done with digital filtering, so you can't turn it off either. A possible way around this is to input the signals digitally, via an SPDIF interface. AM or FM modulating the signals have been discussed too, but I think we came to the conclusion that the resolution would be too low (less than 8 bits).
Q. Considering that the signal frequency we are dealing with is quite low, will it be possible to use the IRDA standard to send data to the PCs? This way we automatically get the isolation. Once the hand shake is established it may be possible to send a modulated stream of packets or something.
Answer from Moritz: A couple of days ago I received from Arizona Microchip a MCP2155 sample. This chip incorporates all the IrDA software protocol. I'll definitely design an IrDA digital board for the Modular-EEG soon. Also maybe with an MSP430F149 microcontroller (12bit ADC).
I have problems with noise, but I'm working on it. I could use some help with designing a good DC/DC converter filter. (Elsewhere: Noise and distortion: Unknown right now)
Trying to find parts that are available on several continents is a *major* headache. Compatible resistors and other passive components and most IC's are fairly easy to find. Enclosures and connectors are not.
Currently, all signals are routed on the bottom layer. This is so people can manufacture their own PCB's by hand. Unfortunately, we might get EMI problems with this. See next point
A few pieces of copper or tin plating, cut to size requires a lot of mechanical skill to put together (or $20 extra at RS Components for factory-made shielding). It is not unlikely it is needed on both sides of the board, since the signals are routed on the bottom layer.
Another way is to cut the board in two and place the front-stage amplifiers in a regular metal box, that goes inside the larger plastic box. This will add about $10, but would be simpler and sturdier. The layout must be redrawn too (not difficult). Maybe this is the way to go...
There is no low-battery detector. One can be implemented with two resistors connected to the microcontroller, at the expense of the decoupling capacitor for the internal reference. It will decrease noise immunity though.
AT90S4433 is nice, but using that would make this device look a LOT more like ModularEEG. The only difference would then be in the small details - like dual vs. single power supply, choice of instrumentation amplifier and filters. Don't want to infringe on Joergs and Moritz' territory... I already am, it feels like.
The MODULAREEG is designed with the following goals in mind: - each module fits on 1/2 EURO (110x80mm) size board. That way it can be designed using the freeware version of the EAGLE layout software. - PCB's can be fabricated at home - Use of conventional parts (no SMD) for easy assembly - up to 3 2-channel EEG amplifier modules can be connected to one ADC module - low price - system can be extended for different additional signals (EMG, ECG, ...)
modEEGdigi01 (schematic dated 11/28/2001) - 2-channel isolated EEG amp with RS232 interface - Uses AT90S4433 microcontroller - Microcontroller does ADC and connects to PC - Sends data to PC over RS232 data lines (RX and TX) - Uses 6N139 Opto couplers - Uses differential uV amplifier - Uses INA114 instrumentation amps and TCL277 op-amps - Input stage modeled after Biosemi designs - Amp on separate board, connects to ADC board w/uC - Not much documentation included yet - PC Cable connectiotion documented - Firmware source and rom not in zip file - Should work with DigitalGuru software
eeg rs232 (schematic dated 09/04/2000) - 2 channel isolated EEG amp with RS232 interface - Uses AT90S4433 microcontroller - Microcontroller does ADC and connects to PC - Sends data to PC over RS232 data lines (RX and TX) - Uses differential uV amplifier - Uses INA114 instrumentation amps and TCL232 op-amps - Uses 7555 timer for calibration circuit - This design is fairly well documented - Firmware source and rom image available - Sample data stream is available - PC Cable connectiotion documented - Test procedures documented - Should work with DigitalGuru software.
GamePortEEG (no date on schematic) - Uses no microcontroller, direct connect to PC - Uses differential uV amplifier - Uses game port interface to PC - I can't tell what the ICs are on the board
comEEG01 (schematic dated 09/03/2001) - 1 channel isolated 8+ bit ADC for RS232 PC interface - Uses no microcontroller, direct connect to PC - Uses differential uV amplifier - Uses INA114 instrumentation amps and OPA2604 op-amps - Uses 7555 timer for calibration circuit - Uses 555 timer for pulse width modulation - Sends pulses to PC over RS232 handshake lines (RTS and CTS) - Pulse range 1mS to 10 uS - PC code must run in DOS only mode (disabling intterupts) - This will not work with the DigitalGuru software - New software required for FFT analysis etc Maybe it might be possible to write Windows/Linux drivers.
I have maintained an open-ended design so that other devices can be added and am working on the GUI now. This process meant going back to the design drawing board a bit, as I needed to reorganize some of the objects, but am knitting things back together now. And, so far, the way everything is designed should be portable between Linux as well as MS Windows, although I have not compiled it under the latter yet. My main focus now, though, is to get the entire device interface stable so that I can then move on to the wonderful world of filters and then finally engage the next phase which, for me, is the incorporation of sound feedback. For me, that's when the real fun truly begins!
[Ed note: An old answer to this read:
There are currently efforts to get the software side of this project
started. We want nothing more then a truly universal biofeedback software.
It will allow easy addition of any computer-connectable biofeedback
device. Several EEG's for neurofeedback will be supported, including, of
course, the groups own hardware designs.]
Yes ! We need you :) ! Please sign up to the buildcheapeeg mailinglist on Yahoo-Groups (see main links in the Web Links section). There will soon be a mailinglist wholly dedicated to software development. Also, please get a username at http://www.sf.net and sign on to the openeeg project. SourceFourge gives us many ressources for software development.
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