From: Doug Sutherland (wearable_at_earthlink.net)
Date: 2001-12-05 16:13:09
Yaniv,
> > 4. design ideas for low cost, single channel eeg.
One other thing to consider is a nicad battery charging
circuit. I'm pretty sure that you're shooting for a
mobile and portable design here. Brainmaster always runs
on batteries, that's one of the ways it deals with power
issues. But it comes with an AC/DC adapter and it comes
with nicad cells inside. The user doesn't need to worry
about batteries, they just plug in the AC/DC adapter
and it charges.
I've done quite a bit of research on power managment
for mobile systems. I have a stack of data sheets in
front of me for all of the maxim charger ICs. I've done
some playing with a National Semi LM3647 charger IC,
and also lots of experiments with Li-ion charging
(which is way too complex and expensive for this EEG).
I could look into battery and charging issues for this
project if that sounds important to you folks. If you
do want a charging circuit, you'll probably want to
add that on the PCB board.
Joerg: are your prototypes running off batteries? Is
battery power mandatory or is AC/DC an option? Do we
need to charge batteries instead of applying the
AC/DC source directly to the circuits? If it needs
to run on batteries than I think nicad rechargeable
with charge circuit onboard makes sense. The ICs for
nicad are not very expensive.
Brainmaster build specs say this:
> Anticipated battery life would be "hours" with the
> 9V battery, "a day or so" with the "AA" cells, and
> "several days" with the "C" or "D" cells. An line-
> powered supply of 8 to 12 volts would also work,
> but would introduce safety issues. One could
> alternatively power the system from e.g. two 9-volt
> batteries, and eliminate the "AGND" circuit below.
> This would also provide more "headroom." But for
> the design integrated with the HC11 microprocessor,
> I have chosen a single 5V supply.
Those are the freeware build specs. The commercial
unit comes with nicad batteries installed and with
an onboard charging circuit. This is a nice feature.
-- Doug
This archive was generated by hypermail 2.1.4 : 2002-07-27 12:28:32 BST