I need to control electrical devices(like bulb,fan...etc) in home with Triac (BT136). I got a circuit from net
when control pin from microcontroller is low the device should be off right? but in my case when I switch on the main switch for the bulb without turn on it by controller, bulb is blinking for the first time. What is the problem Iam not able to understand the trouble.
The standard MOC30xx circuit shown by red_alert is comprised of a RC circuit and a series resistor. The RC cicruit can be understood as a low pass or a snubber, in any case it limits dV/dt for the main and the opto triac. As said it's necessary to prevent triggering by voltage transients, at least with some loads and at sites with unpleasant mains waveforms.
The series current limiting resistor is also required to keep the triac gate current and opto coupler current within rated values.