Re: Dimming

[nicholas@xxxxxxx]

Nigel - can you suggest a Maplin part number? I think that =A320 per=20
lamp is a little too much - a triac plus a few other components cost=20
under a pound...

> You need to determine the zero crossing points, but you re-
synchronise to=20
> each one of them, so the timing after that point isn't very=20
critical.

How could the PIC determine the zero crossing points?

Thanks Nick


--- In ukha_d@xxxxxxx, Nigel Orr <nigel@r...> wrote:
> At 20:43 06/11/00 +0000, you wrote:
> >I find X10 clumsy and unreliable.  I have been able to utilize
a=20
triac, and
> >a variable resistor plus some other stuff to dim a light, but=20
using a
> >variable resistor defeats the point... what I need to be able
to=20
do is dim
> >the light using something like a PIC.
>=20
> There are various options, digital or analogue control, or complete=20
homebrew...
>=20
> Digital, probably most expensive, usually easily expandable, easy=20
interface=20
> to PC, off the shelf.
>=20
> Analogue, 0-10V or similar fed to a controller which handles all=20
the triac=20
> stuff.  Maplin have a module for about =A320 that looks like just
the=20
ticket.
>=20
> Homebrew, you can run a PIC via a dropper resistor from the mains,=20
and take=20
> a dropped, rectified, unsmoothed (phew!) mains signal as an input=20
to=20
> determine the zero-crossing points, then use an output to drive a=20
> triac.  If you want the PIC to have a wired interface to some other=20
> controller, it would need to be opto-isolated, or else you would=20
need to=20
> use an isolated power supply and something like an HCPL-3700 for=20
sensing,=20
> instead of a dropper resistor etc.
>=20
> That last paragraph may mean nothing to you, it could be called=20
overly=20
> concise... which of those 3 would you like to do?
>=20
> >  I don't know how to do this, as at
> >requires precise timing with the mains frequency, as far as I
know.
>=20
> You need to determine the zero crossing points, but you re-
synchronise to=20
> each one of them, so the timing after that point isn't very=20
critical.
>=20
> Nigel


-------------------------- eGroups Sponsor -------------------------~-~>
Create your business web site your way now at Bigstep.com.
It's the fast, easy way to get online, to promote your business,
and to sell your products and services. Try Bigstep.com now.
http://click.egroups.com/1/9183/3/_/2065/_/973618538/
---------------------------------------------------------------------_->