Newsgroups: sci.electronics
Path: utzoo!henry
From: henry@utzoo.uucp (Henry Spencer)
Subject: Re: Switching from 5V to 120V
Message-ID: <1990Feb22.044026.27213@utzoo.uucp>
Organization: U of Toronto Zoology
References: <3709@uceng.UC.EDU>
Date: Thu, 22 Feb 90 04:40:26 GMT

In article <3709@uceng.UC.EDU> dmartin@uceng.UC.EDU (Dale Martin) writes:
>I have designed a circuit using ttl logic chips that activates LEDs.  I would
>like it to activate some 25W bulbs (one at a time).  What is the best approach?
>Could I use relays, or is the switching voltage too low?  How about a transis-
>tor?  Aren't there triacs or something that do just that?  

Relays are possible, but the best way (my opinion) is to use a 3011 or
one of its relatives -- an optoisolator with a small triac as its output --
to drive a larger triac.  The 3011 datasheet (from, e.g., Motorola) goes
into how.  This gives you silent, fast, precise switching.  The larger
triac can be pretty generic, although it's nice to get an insulated-case
type so your heatsink isn't electrically hot.
-- 
"The N in NFS stands for Not, |     Henry Spencer at U of Toronto Zoology
or Need, or perhaps Nightmare"| uunet!attcan!utzoo!henry henry@zoo.toronto.edu