From: sleeper75se (sleeper75se_at_yahoo.se)
Date: 2002-01-14 12:58:19
--- In buildcheapeeg_at_yahoogroups.com, "Jim Meissner" <jpmeissner_at_mindspring.com> wrote:
> Dear Andreas:
>
> Thanks for the reference pages.
>
> Unless I read it wrong, the max rate of the DS275 is 19 KBaud and
> it still needs a power source larger than +5 volts ( a 9 volt
> battery )?
Hi Jim,
where did you see the 19kbaud figure? I must have missed that one.
+12V can be taken from one of the status lines. Anyway DS275 is
looking less and less attractive at the moment.
> The cleanest solution seems to be
> the Fiber-optic IR-LED feeding a short piece of fiber ( 2-3 inches )
> into a fiber-optic Photodiode feeding the
> LT1671 comparator driving a MAX232A.
Hmm, at this distance, regular diodes facing each other, shielded
with a piece of plastic tube painted black (a straw perhaps) might
work just as well.
> That would get a reliable 120 KBaud or better.
> An external 5 volt wall wart power supply may be needed
> which is OK with me.
+5V can also be taken from the mouse or keyboard ports.
Ok, in the name of flexibility what do you think of making room for
several different solutions? Then one can try all of them and pick
whatever is most suitable.
These are the options right now:
Transmission: either fiber (the receiver would be external) or
an "extra-wide" opto coupler.
Reception: Comparator with either a MAX232, a 4053 or nothing at all
Power: RS232-powered or external power (5-12V)
I'm also considering changing to a different microcontroller and
possibly use an external ADC for higher precision, like these:
http://www.linear.com/prod/datasheet.html?datasheet=324
http://www.linear.com/prod/datasheet.html?datasheet=326
> This solution may be more expensive than wished for, but it
> would get the project up and running. ( Very Important! )
Agreed. There are 200+ people waiting... :-)
Regards,
Andreas
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