[TI-H] Re: Link port drain

To: ti-hardware@lists.ticalc.org
Subject: [TI-H] Re: Link port drain
From: Adam Thayer <krevinek@matrix-z.net>
Date: Thu, 31 May 2001 16:17:36 -0700 (PDT)
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.

-Krev

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