I had a look to other posts about Triac and I am pretty sure my problem was not in there.
The goal of my system is to realized a controlled switch for home appliance. Then I designed a power supply system (non isolated) that supply energy to my microcontroler (STM32F030C8T6). It is all working fine.
NOTE: The earth symbol is a mistake, it is a 0V point of the circuit.
As I would like to control every types of appliance I add a snubber circuit for inductive load.
To turn on the applicance I set the STM32 output (logic 1 : 3.3V), and I clear this output to turn off the appliance (logic 0; 0V). This ouptput is a push pull type.
I guess the short 1.8V spikes keep the triac on, but I don't know why these spikes are present.
Anyway, I tried to remove R2 and tied T1 gate to ground in order to be sure that no current is flowing through but the appliance is still on.
Do you have any idea?
Thank you very much.
IMPORTANT: This circuit is dangerous (deadly) as you deal directly with main power. All care has to be taken to experiment.