Path: utzoo!attcan!uunet!zephyr.ens.tek.com!gvgpsa!gold!grege
From: grege@gold.GVG.TEK.COM (Greg Ebert)
Newsgroups: sci.electronics
Subject: Re: Open-gate TRIACs
Keywords: TRIAC
Message-ID: <1446@gold.GVG.TEK.COM>
Date: 12 Sep 90 16:30:54 GMT
References: <1437@gold.GVG.TEK.COM> <1990Sep12.022022.11829@swbatl.sbc.com>
Organization: Grass Valley Group, Grass Valley, CA
Lines: 20

## I(Greg Ebert) write:
##
## I popped open an older "solid-state" relay, which is actually a reed-relay
## with the contacts in series with the gate lead of a TRIAC. 

adams@swbatl.UUCP (Tom Adams - 235-7459) writes:
#
# I'm confused here.  A reed relay?  What provides the magnetic field that
# operates these guys?

The coil is driven by a TTL-level signal, and includes a clamp diode. This 
provides isolation from the AC line. One contact goes to the gate, the other
through a resistor to the anode. When the contacts close, gate current is
provided (for *both* half-cycles).

My only gripe about the relay is that it doesn't have an internal snubber
to limit dv/dt. A di/dt inductor would be handy, too. Geez, what can you
expect from Radio Snack ?

An opto-TRIAC/LED would be more elegant...