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Thread: Paralell port powered little device.
www.piclist.com/techref/ios.htm?key=port
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face BY : Dan Michaels email (remove spam text)



Brusque wrote:
>Hello,
>
>    I'm doing a little device to be attached to the paralell output of a PC.
>I want to take the power to the device (5V, about 40mA max) from the
>paralell port.
>
>    I'm looking at some datas and it says the four control pins are
>open-collector. This means I cannot take +5V from it... :(
>
>    Anyone have already made something like this? How can I do that?
>

40 mA, good luck!! Drawing more than a couple of mA off an
Rs-232 or parallel port is usually more than can be hoped for.
Especially if you want the thing to work off more than just
the computer you initially used.

Open-collector means it "sinks" power, does not source it. It
wants/needs "your" juice.

Sometimes, however, you can get away with wiring several "source"
lines of the **same** voltage in parallel, with each connected thru
a small [eg, 10 ohm] resistor, for some minimal isolation. MAybe can
get a few mA from each, adding up to something usable.

- Dan Michaels
==============

<1.5.4.16.20000605112314.30f7f0f6@lynx.sni.net>

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