An AC Dimmer is used to control the AC cycle. Normally, a dimmer is used to turning the power for lamps or heating elements, it can also be used in fans, pumps, air cleaners, etc.
There many DIY “dimmer” in the internet, but many of them actually used PWM for cutting the AC ON/OFF, this is not good, as it will make the lamp blink; a true “dimmer” should firstly detect the AC zero-crossing point, and then control the triac to chop the AC.
Makerfabs WIFI AC Dimmer chopper circuit is based on Triac BT139, and zero-cross checking circuit, it detects the zero-cross points and then the Triac controlled to chop the AC. Besides, to avoid the problem of AC can not be totally shunted off with Triac, a relay is implemented to make the AC totally On/Off. On-board AC/DC module implemented, so no external power supply needed, suitable for field applications.