I guess technically, the SCR will turn off under specific conditions.  #1 is
if the forward current in the SCR drops below a certain minimum value
(essentially zero for many practical circuits).

-Lawrence
----- Original Message -----
From: "Shawn Yates" <syates@caretech.com>
To: "'Lawrence Lile'" <llile@toastmaster.com>
Sent: Tuesday, February 19, 2002 10:27 AM
Subject: RE: [EE]: SCV vs Transistor


> Thanks for the input.  I didn't know it doesnt turn off.  That seems to be
a
> big difference.
>
> Thanks
>
> Shawn
>
> -----Original Message-----
> From: Lawrence Lile [mailto:llile@toastmaster.com]
> Sent: Tuesday, February 19, 2002 10:00 AM
> To: pic microcontroller discussion list
> Cc: Shawn Yates
> Subject: Re: [EE]: SCV vs Transistor
>
>
> I have an application like this.  The SCR is a triggering device, which
does
> not turn off after it turns on.  This characteristic is useful in certain
> situations.  I have one where the SCR crowbars a coil which MUST stay off
> after a certain time, no matter what.  No matter whether the PIC hangs,
> reboots, gets hit by a brownout, and so on.
>
> In quantities a TO-92 SCR will cost you US$0.06 to 0.10, whereas a 2n2222
> will cost you about a penny, so most people don't use an SCR unless it is
> really needed.
>
>
> --Lawrence Lile
>
> ----- Original Message -----
> From: "Shawn Yates" <syates@CARETECH.COM>
> To: <PICLIST@MITVMA.MIT.EDU>
> Sent: Tuesday, February 19, 2002 8:47 AM
> Subject: [EE]: SCV vs Transistor
>
>
> > I know this is a basic question, but I need to ask it.
> >
> > I have always used a transistor driven by the pin of a PIC to turn on
and
> > off high current devices (relays, buzzers whatever).  I saw a design
where
> > someone was using an SCR.
> >
> > Is there any operational difference when the application is switching
not
> > amplifying?
> > Is there a signifigant cost difference?
> >
> > What I am getting at is why would one use and SCR instead of a
transistor.
> > They are even in the same TO package.
> >
> > Any input appreciated.
> >
> > Shawn
> >
> > --
> > http://www.piclist.com#nomail Going offline? Don't AutoReply us!
> > email listserv@mitvma.mit.edu with SET PICList DIGEST in the body
> >
> >

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