--- In "Yan Seiner" <> wrote:
>
> --- In Joel Winarske <joelw@> wrote:
> >
> >
> > > I'm kicking around the idea of controlling an ordinary 120 VAC
> > > incandescent light (actually a 150W heater).
> > >
> > > I'd like to control the heater based on the temperature of the
surface
> > > beneath it. I need to control it to approximately 105 deg F (more or
> > > less; great accuracy is not needed here.)
> > >
> > > I've found some basic PIC circuits on the web but I wonder if anyone
> > > here has any suggestions, both for the temp probe and for the heater
> > > control.
> > >
> > > As this will most likely be a one-off, an inexpensive commercial
> > > solution would be fine.
> > >
> >
> >
> > You would need:
> > 1. Zero Crossing input
> > 2. DC Power circuit
> > 3. PWM / Triac Control
> > 4. Load current protect circuit
> > 5. temp measurement - A/D
> > 6. Control interface - RS485/CAN/RS232
> >
> > The NXP LPC2xxx is a good fit for this.
> >
> > How many channels do you need?
> > How far from the controlling device do dimmer channels need to be
> located?
> >
>
> Sorry, I should have been more detailed....
>
> I want to run the temp probe into the A/D inputs on a TS7xxx board,
> and then have the board control the heater.
>
> The reason for this is that I also want the ability to set up a webcam
> and multiple control channels, and I want web-based programmability.
>
> So I'm really looking for a 120VAC dimmer that can be run by a TS7200.
> All I've been able to find are PIC based designs, which I could
> probably adapt, but I am not a hardware person...
>
> --Yan
>
Depending on the thermal conductivity and thermal capacity of what you
are controlling, and the precision you need, may only need a
thyristor: usually the time constants of temperature controlled
systems is quiet large (like tens of seconds), so just turning the
heater on and off is enough. If this is the case you won't need a PWM
output either, just binary.
Note that by saying a thysritor I mean any on-off device: triac, or
relay too. A thyristor is rectifying, so you'll get at most 1/2 the
power unless you use two of them.
Gonzalo
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