I am sharing the solution I found for this problem. The problem comes from the phase shift of voltage/current due to the coil and the diode, as well as the non-zero-crossing optocoupler. The triac is activated by current, and with the phase shift, it activates in the middle of the sinusoid. Due to the zero-crossing photocoupler and the half-wave caused by the diode, there is not even a quarter of a wave left to power the coil.

To solve this problem, I have found several solutions:

Place a return diode with a resistor (very bad idea) Replace the triac with a relay (good idea, but not in my case) Replace the optocoupler with another zero-crossing one (bingo!)

I hope this can be of some help to someone.

I am sharing the solution I found for this problem. The problem comes from the phase shift of voltage/current due to the coil and the diode, as well as the non-zero-crossing optocoupler. The triac is activated by current, and with the phase shift, it activates in the middle of the sinusoid. Due to the zero-crossing photocoupler and the half-wave caused by the diode, there is not even a quarter of a wave left to power the coil.

To solve this problem, I have found several solutions:

• Place a return diode with a resistor (very bad idea)
• Replace the triac with a relay (good idea, but not in my case)
• Replace the optocoupler with another zero-crossing one (bingo!)

I hope this can be of some help to someone.