Fan Regulator Circuit | Light Dimmer | AC Load control using TRIAC – DIAC

Fan regulator circuit / Light dimmer

The fan regulator circuit or light dimmer circuit is one which intensity of light or fan speed controlled by regulator. It is simply we called as fan regulator. The light intensity is controlled by fan regulator so it is also called as light dimmer.

Components of fan regulator circuit or light dimmer

• Lamp
• Triac
• Diac
• Variable resistor
• Capacitor

Working of fan regulator circuit or light dimmer

• The fan regulator circuit using TRIAC – DIAC is shown in the figure. The TRIAC and DIAC are bi – directional therefore they are used for alternating circuit. 
• The R_L is load resistance / lamp or two terminal of single phase winding. The charging of capacitor is done through L – R_L – R – C – N path.
• When voltage across capacitor becomes equal to break over voltage of the DIAC, the DIAC turns on. 
• As soon as the DIAC turns on, the discharging of capacitor is done through C – DIAC – G – MT1 – C path. 
• Now the gate terminal of TRIAC gets signal and TRIAC turns on. 
• The load resistance complete its path through L – R_L – MT1 – MT2 – N. The charging rate of the capacitor is depends upon the variable resistance R. 
• The firing angle of the TRIAC depends upon variable resistance R. 
• The charging rate of the capacitor is less for higher value of resistance resulting firing angle of TRIAC increases and voltage across load reduces. 
• Similarly the load gets higher voltage for low value of resistance due to less firing angle.  

Circuit diagram of fan regulator circuit or light dimmer

Finally Remember

High variable resistance – Firing angle increases – Low voltage across load

Low variable resistance – Firing angle decreases – High voltage across load

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