How do you chop a AC waveform such that I get 4 different dimmer levels? I know that the power isn't linear with respect to angle...Is this something people do by trial and error?
Define "different." 0-25-50-100%? 0 and 100 are easy. 50% can be easy if skipping every-other-cycle or half-cycle. For arbitrary angles, watch this video.
reading the datasheet the VREG_2V7 is a 2.7 V internal regulator output st.com/resource/en/datasheet/stusb4500.pdf and the typical application example in the datasheet doesn'
It looks like the sparkfun module is designed to either accept an external VDD, or use an internal 2.7V regulator. The diode, D4, prevents an externally-supplied VDD from back-feeding the 2.7V regulator
