Powering circuits from serial port

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Article #19343

#19343

From: Leonard Harris
Date: Fri, 01 Jul 1988 16:45

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I have a small circuit (3 ttl) that hangs off a rs232 serial port.  Rather
than add a power supply, is it possible to power this directly by stealing
the CTS/DSR signals and converting to 5V with a zener diode?  Also, other
than using the MAX232 level converter, is there an easier (and cheaper) way
of converting ttl to rs232 levels - again without using an external power
source.  (the distance signals are travelling are less than 3 feet)
Thanks
/leonard

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Message-ID: <1988Jul1.124545.14929@gpu.utcs.toronto.edu>

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Path: arc1-ca.pugleaf.net!utzoo!utgpu!lharris
From: lharris@gpu.utcs.toronto.edu (Leonard Harris)
Date: Fri, 1-Jul-88 12:45:45 EDT
Message-ID: <1988Jul1.124545.14929@gpu.utcs.toronto.edu>
Organization: University of Toronto Computing Services
Subject: Powering circuits from serial port
Newsgroups: sci.electronics