fan regulator

Fan Regulator/AC dimmer

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Electronic Fan Regulator

AC Light Dimmer circuit

Resistive fan regulator

We first discuss the conventional big-size resistive fan regulator. Conventional Old ceiling fan regulators use resistive wire to connect in series and there are multiple points to connect the regulating knop switch to adjust the speed. This type of regulator works on a full resistor load between load and source to make a required disruption to current and voltage drop. A lower speed means higher resistance.

When setting the at low speed then the knob is going to flow of current through maximum Length of resistive wire. At medium, current flow by the middle point of the resistive wire and at High speed there is no resistance means at the starting point of the resistive wire is connected with the fan supply.  

These regulators need more space and look like a big rectangular box having a circular knob on it. These are also known as resistive regulators. The box consists of a wire wound resistor with different taps that are connected in series with the motor of the fan. Nichrome wire used as resistive material in these, so a more amount of power loss occurs by Heat produced through these resistive wires.



AC dimmer circuit 

AC fan regulator circuit

The main advantage of these type regulator is cheap, high durable and no humming noise produced in a fan at low speed.

Disadvantage – Even at low speed they consume the same power as high speed because resistive wire acts as a load in series with fan.  Power loss unnecessary by heat.

Electronic Fan regulator

There are basically two types of electronic fan regulators available in market

  1. Triac based
  2. Capacitor based

Triac based Regulator/Dimmer

In the Triac based electronic fan regulator circuit there are mainly three components used.  Resistor, One Capacitor, One Diac, And One Triac. TRIAC is a semiconductor device belonging to the family of thyristors. This is directly used to control the speed by holding and releasing the current flow.

AC dimmer circuit fan regulator circuit diagram

Working of Triac based Electronic fan regulator

In this circuit, A Diac is connected with the gate terminal of triac. One side of the Variable resistor connected with to Triac terminal through 22k resistor and another side of VR connected with a capacitor is connected with Diac.

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When the voltage across Diac is cross the level of VBO Then it gets triggered and it turned on. For DB3 The VBO is 32v (+/-4v). This means When the voltage across DB3 reaches 32v then it turns on and the current will flow through it. Diac is made by the combination of two diodes in an alternative direction, Two diodes are combined in opposite to each. Diac provides the gate signal of Triac and according to the gate signal, it passes the supply from MT2 to MT1.

Resistor and Capacitor make an R-C circuit to provide timing delay and timing constant for Diac input and then by the timing constant pulses it is able to create Limited voltage through triac and Load gets regulated input supply.

Diac gives fully DC output for both negative and positive cycles, this is used for the triggering of Triac.


   220v AC Fan regulator circuit 

At first, when the supply is on, triac is in Off state, the capacitor gets a signal voltage through the Fan and resistor and this capacitor is charged. When the capacitor is fully charged,  the capacitor stores power, and Diac gets turned On and Triac also turn on and the supply passed through triac. As Triac turn ON Capacitor is Discharged. Again Capacitor gets current through the resistor bypassing the Load and input line and Charged. Capacitor Discharged by giving the power to Diac and therefore again Triac turns on because Diac gives a signal to the gate terminal.

This Charging and Discharging of capacitor randomly occur and Triac turn ON-OFF Randomly also. The Timing Rate of charging of the capacitor is increased by the increase of the resistor value. So, the Combination of the Resistor and capacitor in this circuit makes a timing delay.

A Protection circuit can be included for Triac protection by adding of the resistor and a capacitor in series with the parallel of Triac. This is called the Snubber circuit, this is required only in inductive load like motor/fan. not for resistive load.

ac dimmer fan regulator circuit diagram

diac triac dimmer waveform

0.1uf 400v capacitor

BT136 TRIAC Pin Diagram and Symbol


triac dimmer firing

When we increased the timing of the charging rate of the capacitor then triac gets a delayed gate signal and it gives less voltage supply to Load.

Advantage – Low Power consumption at Low-speed Level. Cheap and Smaller Size

Disadvantage A noise sound like humm is produced by FAN when Low speed.

Capacitor based (Noiseless fan regulator)

In the capacitive Regulator there are some capacitors connected in series with the load and each capacitor has a resistor in parallel. Capacitive Regulator is very popular and easily available in the market. This is some costly than the triac based regulator. But the Result is better than the Triac regulator.

P 20180517 122525

fan regulator circuit

The advantage of this regulator is there is no noise humm sound produced by FAN. At Low-speed low power consumption.

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8 thoughts on “Fan Regulator/AC dimmer”

  1. Hello Aman,

    Nice explanation…

    But can we connect two Capacitor based step type regulators in series? I want more control over the fan speed than what is possible with those 5 steps. Technically this way we should get 20 steps if we connect two 5 step in series. But some steps will be redundant; so we might get 10 usable steps this way.

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