Ds1820 -> pid -> pwm

[malc-c]

The easiest way is to use a solid state relay as it isolates the load from the PIC and is easy to drive (it's basically just a LED). But to give a more detailed answer we'd need to know if the heater is AC and you by PWM really mean phase angle control. Or if it's DC and you intend to use the CCP-module in the PIC to produce a PWM signal - or (if it's either AC or DC) you intend to create a slow speed PWM with a period of several seconds or longer (I beleive this is what Malcolm did) where the fact that a triac or solid state relay for AC doesn't switch off until next zero crossing doesn't matter.

/Henrik.

I agree, an SSR is the simplest way to interface the output from a PIC to mains device. In the development of the thermostat project I'm now using zero-crossin opto-triac isolators to drive 16A triacs, but the original prototype used 4A SSR.

As Henrik stated, my thermostat project uses low speed pwm to apply power to the heaters, the result is that the heaters remain at a nice stable temperature rather than the normal method of heating which results in large temperature swings

Here's an example of the frequency