KerimF
Advanced Member level 5
- Joined
- May 17, 2011
- Messages
- 1,554
- Helped
- 376
- Reputation
- 760
- Reaction score
- 379
- Trophy points
- 1,373
- Location
- Aleppo city - Syria
- Activity points
- 13,095
Since both FANs and fluorescent lamps are inductive I suggest for on & off that the triac be triggered by a DC current as the simplest reliable solution. But this consumes a relatively high power (current). To reduce the gate average current while continuously triggering it, one may pulse it continuously with a total period of 80us (typical value I usually use) with a duty cycle say 25% (20us on and 60us off). You can experiment with a different duty cycle also the pulsing period (smaller is better but this likely reduces the duty cycle). I give here (80us, 20us on) values to start with if you like reducing the current consumption (instead of DC) since the optimum timing depends on the triac type (power and trigger speed) and the inductive load (inductance and time constant).
Note1:
The pulsing could be generated with a timer IC (555) and the MCU drives its reset pin (low=off and high=on).
Note2:
The DC triggering can be used only with 'random-phase optoisolators triac' drivers or if the output terminal for the gate of the power triac is connected to one of the two voltage supply terminals (usually to the positive Vcc, since the gate sensitivity, in the 4 quadrants, is typically higher, hence requiring lower current, if the gate current is out ot it).
Note1:
The pulsing could be generated with a timer IC (555) and the MCU drives its reset pin (low=off and high=on).
Note2:
The DC triggering can be used only with 'random-phase optoisolators triac' drivers or if the output terminal for the gate of the power triac is connected to one of the two voltage supply terminals (usually to the positive Vcc, since the gate sensitivity, in the 4 quadrants, is typically higher, hence requiring lower current, if the gate current is out ot it).
Last edited: