My questions are based on this project http://www.electronoobs.com/eng_circuitos_tut20.php
I have built your AC triac dimming circuit with a potentiometer, and 110VAC 60Hz mains voltage. The first time I ran the program, the lamp dimmed properly. However, once I turned off power and turned in on again, the lamp did not turn on. I changed out the optocoupler it fixed the problem, but it happened again. I placed my oscilloscope across D8 (connected to the EL817 optocoupler) and GND and measured a sine wave. I understand this should be a square wave, which is what I measured when the lamp actually dimmed.
Can you please help me understand why I am getting a sine wave across D8 and ground? Why does the circuit work once and then stops working when I go to use it again? How can I prevent these issues from happening in the future?
Thank you in advance