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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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