[TI-H] Re: Link port drain

To: <ti-hardware@lists.ticalc.org>
Subject: [TI-H] Re: Link port drain
From: "Ronald Teune" <rtwolf@gmx.net>
Date: Tue, 5 Jun 2001 10:55:41 +0200
Reply-To: ti-hardware@lists.ticalc.org


>--- "Ronald Teune" <rtwolf@gmx.net>
>> wrote:
>>
>>
>>Hi all,
>>
>>does anyone know how much drain (I mean milliAmperes) a link port could
>>give? I want to connect my TI to LEGO :o)
>
>I would say 0.5 mA, since the internal schematic is that the 5V output
signal goes through a 10k resistor before the jack is connected, and of
course the 400 ohm resistor, NPN transistor/etc. after the jack. You would
draw 100% of the current at 0.5 mA, but that is roughly what is available.
One doesn't need that much to drive a signal between two things. If you want
more power, you can do this:
>
>Hook a transistor's base to the link port's pin you are using for signal,
and have a 9V battery hooked up with a 100 Ohm resistor before the
transistor. Then hook the load (the Lego stuff) after the transistor, and
hook that to ground (the battery's negative terminal). This would give you
90 mA to play with, with electronic switching done by the link port. If this
is what you are after BTW.

Like this?:
[monospaced font]


              ______ 0 load + ___ + 6 V (four batteries)
             /
     __    |/
in -[__]---|           <-- NPN BC548
           |\
  100 ohms   V
              \___ 0 V




>-Krev
>
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