Homebrew PCBs

>> demolitron wrote:
>> <SNIP>>
>> 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.

> DJ wrote:
> Would I need a 60hz sync signal for this?  Or
> can it run much slower than that?

Detect the Zero crossing and then trigger an
SCR/Triac a proprtional amount beind the zero
crossing.  This option is only suitable for
small resistive loads (like a laminator)

or

Full Wave rectify the AC (No need for filter
caps) then use a FET at what ever (high) PWM
freq you like.  This method is only good for
things like resistive loads that don't care
that it is now 110/240V DC rather than 110/240V
AC.

or

Detect the zero crossing and turn on/off for
full cycles for a proportional amount of
50/60Hz cycles.  Your on/off cycle time will
have a minimum "legal" amount of time.