randynealpetersen:
So is it important to leave the heater on for a period of time to make it effective? Like a 1/2 a second or something? Since I don't have a zero-cross detection shouldn't I be leaving it on for several cycles. Have like a minimum on time?
If you just buy an off-the-shelf PID temperature controller (like 1/16 DIN PID Temperature Controller (For SSR) [SYL-2352] - $42.98 : Auber Instruments, Inc., Temperature control solutions for home and industry), as is pretty common for DIY sous vide cookers (and what I did), it will do just what you're suggesting. You can adjust the time base, but it defaults to 2 seconds. So, 10% power would be 0.2 sec on and 1.8 sec off, 50% would be 1 sec on and 1 sec off, etc. An SSR is the most common device used to switch the heater on and off, as a mechanical relay would quickly wear out from the on/off cycles. Properly tuned, and with an appropriate temperature sensor, these can hold temperature to within a few tenths of a degree without a problem.