new thermostat on reptile basic

[spyderrobotics]

I also went away from the dimming method of proportional control. I went with a duty cycle approach or “pulse”. Basically we chopped up a 1 second period into about 900 parts. We gradually increase or decrease the number of parts of a second the power stays on. The trade off is this is not too good with incandescent light bulbs for heating. They will blink.

In theory this would not work. Zero crossing happens 120 times per second (two half cycles with a standard and inverted wave at 60hz). The component that controls the AC (Triac) can be turned on anywhere within the half cycle but can not be turned off manually. It has to wait for the voltage to drop back to zero before before it "releases". It can then be refired on the next half cycle. Pulsing the circuit more or less times makes no difference because onces its fired you are along for the ride. So the maxiumum number of time slices per second is 120 with a triac. The only exception would be if it was mosfet controlled in which the DC current can be turned on/off at will. Sorry, I had to.

Dion Brewington
Owner, Spyder Robotics