Re: TI-H: IR Link
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>I know Marc Levine has designed an IR Link for TI calcs
>but as far as I know, the current design shouldn't work.
I agree.
>Has someone built it and tested it?
Not to my knowledge.
>If it doesn't work, I might design a new one.
COOL! I'll help...
>I have no experience in building IR devices and not
>much experience in electronics either,
GOOD GOD! ;)
>but I think that with some help from this mailing list it
>would be possible for me to build a working IR link for
>two or even more TI calcs (an IR LAN in a classroom
>would be really great! :) ).
Okay. Before we go ANY further, let me say this:
THERE IS NO WAY TO LINK MORE THAN TWO TI-85s TOGETHER WITHOUT THE USE
OF A MICROCONTROLLER OR MICROPROCESSOR SOMEWHERE IN THE CIRCUIT.
(Been there, done that.) It just isn't possible to do with simple
logic gates, and the two wires on the TI. You need more power than
those devices can provide. I'm NOT trying to shoot down any ideas,
just to make a point here. Got it? PLEASE DON'T FLAME ME, at least
not on the lists.
>It should probably be connected to the link port.
Good idea! ;)
>The main problem in IR is that you have only one
>channel (unless you want to experiment with different
>wavelengths, but I'm not going to do that), so you must
>somehow modulate the R and W signals in just one channel.
No, in fact this WOULD be easy. All you need to do is get two 556
timers, and hook them up so that they occilate at a HIGH frequency,
one slightly different than the other. (You do NOT need to even
THINK about wavelengths) Then hook up a detector (GP1U52X -- R.S.
Cat. No. 276-137; Includes everything you need to know, and
schematics, which would only need to be modified slightly for our
purposes) to two 567 Tone Decoders, one to detect each frequency.
Believe it or not, this can all be done with 2 NE556 Timer Chips and
2 567 Tone Decoders (and of course, the IR detector module and a few
other components). This circuit IS relatively small, especially when
on a PC board.
Hmm... I think I'll try to build a prototype this week.
>Then my questions:
>Does this sound stupid?
NEVER! It is VERY POSSIBLE. Just don't get in over your head with
those microcontrollers; keep it cheap and simple, like my idea.
>Have I forgot something?
Not really... (think u remembered TOO much <G>)
>Any ideas?
See above.
>Anyone willing to help?
Of course. Anytime. I have quite a bit of experience with IR
circuits... :)
>Is there actually any interest in the idea or is everybody just
>expecting a working radio link?
Well, the RTLink is a bit more practical (it goes through walls), but
IR should be pretty simple.
Cheers,
____
~Keith
FFNP69C@PRODIGY.COM
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