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From: cgordon@vpnet.chi.il.us (Crash Gordon)
Newsgroups: sci.electronics
Subject: CMOS/TTL -> Relay
Message-ID: <2743289c-571.1sci.electronics-1@vpnet.chi.il.us>
Date: 16 Nov 90 02:55:03 GMT
References: <1990Nov14.053607.5352@cs.wayne.edu>
Lines: 16


Probably the neatest way to pull this off is to use something like the
ULN2003 (Motorola MC1413).  This IC contains an array of seven darlington
power switches, with biasing resistors and protection diodes included to
allow low-side swithing of inductive loads.  (I think there's also a ULN2803,
which has 8 drivers.)

One pin is connected to ground, and one to the relay power supply.  Then,
the common side of the relay(s) is/are connected to the relay supply, and
the other side(s) go to the IC.  Applying a logic high to the switch input
pin will pick up the relay.  (The data sheet makes this all pretty
obvious)  The chip can switch 500 mA.

-----------------------------------------------------
Gordon S. Hlavenka            cgordon@vpnet.chi.il.us
Disclaimer:                Yeah, I said it.  So what?