"demolitron" <
ahardinger@...> writes:
> Personally, I love this project as I seem to want to MCU everything I see!
Well, it will show up on my web site eventually.
> With an MCU you could implement a Proportional Integral Derivative
> (PID) algorithm and apply a PWM signal to the Triac giving very fine
> and nearly linear (depending upon the PWM frequency) power control to
> the heater element.
Would I need a 60hz sync signal for this? Or can it run much slower
than that?
> Using the SPI thermocouple interface would eliminate the need for an
> MCU with an ADC
Need that for the potentiometer reading anyway, and most mcu's come
with adcs - at least, small ones that are "good enough" for a pot
reading.
> as well as the commensurate fussy analog signal conditioning.
Agreed :-)
> If you wanted to save even more cost you could replace the LCD with
> three 7-segment LED displays and replace the POT with two switches,
> one up one down.
The LCD is only $8.30 and I have pots in my junk boxes. Using an LCD
means I can choose an MCU with fewer pins (less $$) and need a smaller
power supply.
> I don't know what your MCU background is so please forgive me.
I work for Red Hat writing embedded compilers.
> The math for a good PID control is a bit complex for a little 8-bit
> MCU but well within reach.
I tend to use the Renesas R8C chips, which are 16 bit. I have a spare
R8C/27 from a past project, which has plenty of ram and flash. 20 MHz
clock, 10 bit adc, etc. 32 pins. Not the cheapest of their chips -
$5.20 - but I already had it, and I've used them for lots of projects
so I have all the tools I need. It also runs at 3.3v or 5v which
comes in handy.