use courier font
+5V--R---+----+----
| |
zener |
| A2
----G Triac
| A1
C |
| |
GND------+----+----
zener cathode to +5V
C: 1nF
R: polyswitch
- on over-voltage a current of 10..50mA is flowing through zener->G->A1
(for a very short time)
- after firing of the triac, output voltage is 1-2 volts, the gate current
is zero, R is getting hot
- if the current is dropping below the hold current (10..200mA) the triac
is switching off, R is cooling down ...
M.
On Thu, Feb 13, 2003 at 06:14:03AM -0800, Robert Ritchey wrote:
> Hi Matthias,
> OK, I got the data sheet. Its still not clear to me if the zener goes
> between the gate and the 5V input or the gate and ground? Even
> with the data sheet I don't quite understand how a Triac works. I
> have looked through my books here and have not found a write-up
> on this. I don't understand how this is triggering using the zener.
> Thanks,
>
> At 12:03 AM 2/13/03 -0800, Matthias Weingart wrote:
> >you need a datasheet: e.g.
> >http://www.st.com/stonline/books/toc/ds/336.htm
> >You can see the terminals A1 A2 and G in the picture :-).
> >
> >Normally the gate threshold is approx 1 volt @25C (with my T1235 here).
> >Simply try it out. I think it depends on terminal voltage (can be 600V)
> >temperature and so on. Some of your parameters are fixed and known; so it
> >is not a big problem.
> >
> >Matthias
> >
> >On Wed, Feb 12, 2003 at 12:56:19PM -0800, Robert Ritchey wrote:
> > > Hi Matthias,
> > > Sorry to bother you again with this but the Triacs I found in Digi-Key
> > > (which I am pretty much reliant on for prototyping) have gate thresholds
> > > of 0.2V at 110C to 2.0V at 25C. Some are higher at 2.5V You mentioned
> > > a 1.0V threshold. Also, I am not sure what A1 and A2 are connected to.
> > > Is A2 ground and A1 my input voltage? Like I said, I know nothing about
> > > Triacs and have no literature on their operation. The data sheet is not
> > > a lot of help.
> > > Thanks,
>
> -Bob
> --------------------------------------------------------------------
> Robert Ritchey
> Quest Engineering & Development
> 1328 East Cottonwood Lane
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>
> --
> Author: Robert Ritchey
> INET: [EMAIL PROTECTED]
>
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--
Author: Matthias Weingart
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