Re: TI-H: Add LEDs to your link cable!
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Re: TI-H: Add LEDs to your link cable!
> >I have heard a lot of people saying my design won't work, but it
> >DOES. I haven't yet tried it on the TI-TI link cable, but I have
> >successfully built this for the parallel link. With the 10,000 ohm
> >resistors, the LEDs draw an extremely small amount of electricity
> >(about .0003 amps) which is far too small to affect any link
> >transmissions.
>
>
> It works for the parallel link because the parallel link is sourcing
> all the current.
>
> But, the TI link itself can only supply maybe .2 or .3 milliamps
> before it will be pulled to ground (probably less). The max
> theoretical current out of the linkport is 0.5 milliamps but that is
> impossible to utilize since the voltage at that current is zero.
Tonight, to test if the LEDs would work on a regular TI-TI link, I
unplugged my paralled link from my computer to prevent any other
source from suppling electricity, and then plugged it into my TI-85
calculator. Both LEDs lit up fine, and the calculator kept right on
working fine. Now if either of the lines had been pulled to ground,
the calculator would have slowed WAY down (almost locked up) because
it would be expecting a link transmission. So, the LEDs should
definately work with two TIs, seeing that then there would be two
calculators to supply the current. If it doesn't then just increase
the value of the resistors. And one more thing that I just thought
of... when transmitting through the parallel link, there are times
when for one of the lines, the parallel side will be at a logical 0
and the TI side will be at a logical 1. Therefore, at these times,
the LEDs will only be drawing current from the TI, and if the LEDs
interfered at all with the transmission, then the LEDs would not even
work on the parallel link, which they do.
-Ed Plese
eplese@lnd.com
http://www.geocities.com/siliconvalley/bay/2267