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Re: diac, triac
Subject: Re: diac, triac
Date: Fri, 9 May 1997 01:47:54 +0500
From: "Alfred A. Skrocki" <alfred.skrocki-at-cybernetworking-dot-com>
To: Tesla List <tesla-at-pupman-dot-com>
On Wed, 07 May 1997 08:57:12 -0500 David Huffman
<huffman-at-FNAL.GOV> wrote;
> Does someone know what purpose the diac or avalanche device on the
> gate of a triac serves? Does it have something to do with slamming
> the triac on instead of gradually?
The purpose of the avalanche device on the gate of a triac is to set
the minimum turn on voltage. Triac's can not turn on or off
gradually, they are an all or nothing type device either they are
conducting or they are not. The variability in a dimmer is due to a
voltage divider potentiometer that controls what percentage of the
line voltage is impressed across the avalanch device and ultimately
the gate to triger the triac into conduction. Once a triac is
conducting it will continue to conduct untill the supply voltage
drops to zero then the triac will be restored to it's no conducting
wait state.
Sincerely
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Alfred A. Skrocki
alfred.skrocki-at-cybernetworking-dot-com
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