Re: 8 channel E*G with AVR and bluetooth

Here is my latest filter design.  This is probably the final design.  If
the leakage from the diodes is too high, they can be removed.  The chip is
supposed to handle 100ma, which is a pretty good spike.

Input on this design from:

Joerg Schulze-Clewing
http://www.analogconsultants.com/

(He didn't ask for attribution, but I thought I should mention him!)

Grant


On Tue, Jan 21, 2014 at 11:12 PM, Grant Stockly <[email protected]> wrote:

> Not wanting to wait for a kickstarter I decided to throw together a board.
>
> My specialty is NOT analog circuitry, however I have a seasoned analog
> engineer friend who is going to check the design for me.  Seasoned as in
> used to work with vacuum tubes.  ; )  He is currently a consultant and
> usually has a medical or aircraft client on the bill.  I'm very lucky to
> have his donated assistance.  He has NOT looked at these drawings yet...
>
> He isn't a specialist in this field, so I was hoping a few on the list
> would help.
>
> The main features are:
>
> -ADS1299 front end
> -ATmega168 running at ~11mhz (+ odd frequency digits for perfect serial
> data rates) to be a SPI to serial bridge and limited intelligence
> -RN-41 serial bluetooth adapter for communicating with a computer
> -LDO regulator with a low voltage shutdown circuit at 3.1v, startup at
> 3.25v
> -Lithium battery cell with onboard charger (A DPDT on-off-on switch moves
> the battery from charger-off-device to provide 100% isolation)
>
> Any comments/suggestions would be great.  If it works I plan on building
> 4-5 for my use, and could possibly order PCBs for others.  I plan on only
> ordering 3 prototype PCBs
>
> Gerber files will be available to anyone who wants them too.
>
> Other than more blinking lights, power supplies for the ADS1299, and
> changes to the filter stage, this should be a good start.
>
> I'm leaning on removing the integrated charging circuit and also changing
> the AVR to a surface mount package.  I plan on waiting until routing takes
> place to make the decision on the AVR and just need to think hard about the
> charging circuit.  That might come down to PCB space too.
>
> If the attached files don't make it through the list serv,
> Here is the root:
> https://drive.google.com/file/d/0B02kTn5EGn1bNEF0elRfYjNEdGs/edit?usp=sharing
> Here is the filter:
> https://drive.google.com/file/d/0B02kTn5EGn1baVBXMnEwdUxJMWc/edit?usp=sharing
>
> Thanks,
> Grant
>

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