Re: bluetooth eeg

I have had results using plain op-amps, though the word "results" is used loosely.

I built an instrumentation amplifier like the one found in something like an INA333, but it turns out that they're really picky about their resistor matching.  Therefore, I will instead attempt the signal capture of ECG (yes, I know, EEG list and all that) with a device that's not been developed yet, but I know that it's loads cheaper to just shell out the money for an IN-amp, rather than cheaping-out with op amps and trying to trick them into presenting signal without noise.

In the meantime, I did a little work with negative feedback and automatic gain control, and realized that the better amplifiers have more stages that are run with lower gain per stage with negative feedback on the common mode input terminal.  That's the device that hasn't been developed yet.  Single-ended operation is possible.

I'm going to buy a couple of IN-amps over the next few days to see if I can capture EEG on an ancient oscilloscope, and then modulate it for a sound card to pick up on its microphone input - analog from the start.  The computer can be used to record the analog signals to a .wav file (or in my case, .ogg) that can be viewed, and dare I say, heard, at any time in the future.  This raises a question - can brainwaves be used to modulate a binaural beat generator, as if it were a form of biofeedback?  Gotta try this! *returns to mad scientist lab*

Kevin
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On Thu, 11/6/14, wikitronic <[email protected]> wrote:

 Subject: Re: [Openeeg-list] bluetooth eeg
 To: [email protected]
 Date: Thursday, November 6, 2014, 9:43 AM
 
 Hi,
 I'm new to mailing list so I am trying to reply to the
 group to keep the discussion going.
 
 I am a hobbyist and not a professional engineer. I can
 benefit from more ideas.I am not trying to choose the best
 components ,just what is most common for components. Here is
 the schematic for the sound card eeg dual channel fm circuit
 you are probably familiar with.
 
 http://openeeg.sourceforge.net/doc/hw/sceeg/DualChannelFMUnit-Sheet1.jpg
 
 I was planning to use tl084 quad opamps instead of the
 ad706 and I have am ad620 and an ad8221 for the
 instrumentation amplifier.
 
 I want to use an hc-05 bluetooth serial module.
 
 For the microcontroller I chose a pic16f1788 because
 it has a uart for the hc-05 a 12 bit adc and enough memory
 to buffer the samples from the adc . I want to buffer the
 adc samples because I had previously found variation in the
 transmission rate that might interfere with sample timing.
 So far I think I can get 8k sample rate for each channel.
 
 I have a stellaris(or whatever it is called now) dev
 board but I'm not sure it would be necessary.  
 
 I know the best way to decide will be to build
 something but I thought I might get some good input from the
 group first. I'm not set in my design but you know how
 long it takes to ship new parts.
 
 The objective is to make a double sided smt board
 that runs off a 9v battery and  fits in a headband.
 
 thanks
 
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