We first discuss about the conventional big size resistive fan regulator.Conventional Old ceiling fan regulators uses 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 fully resistor load between load and source to make a required distruption to current and voltage drop . A lower speed means higher resistance.
When set the at low speed then the the knob is goes to flow of current through maximum Length of restiive wire. At medium, current flow by the middle point of resistive wire and at High speed there is no any resistance means at starting point of 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 a wire wound resistor with different taps which is connected in series with the motor of the fan. Nicrome wire used as resistive material in these, so a more amount of power loss occure by Heat produced through these resistive wires.
The main advantage of these type regulator is cheap , high durable and no humming noise produced in fan at low speed.
Disadvantage – Even at low speed they consumes same power as high speed because resistive wire acts like a load in series with fan. Power loss unnecessary by heat.
There are basically two type of electronic fan regulators available in market
Triac based-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 .
Working of Triac based Electronic switch–
In this circuit A Diac is connected with the gate terminal of triac. One side of Variable resistor connected with to Triac terminal through 10k resistor and and other side of VR connected with a capacitor is connected with Diac .
When the voltage across Diac is cross the level of VBO Then it get triggered and it turned on. For DB3 The VBO is 32v (+/-4v). Means When the voltage across DB3 reach 32 then it turn on and current will flow through it. Diac is made by combination of two diode in alternative direction, Two diodes are combined in opposite to each. Diac provide gate signal of Triac and according to gate sinal it passes the supply from MT2 to MT1.
Resistor and Capacitor makes a 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 get regulated input supply.
Diac gives fully DC output for both negative and positive cycle, this is used for the triggering of Triac.
At first when supply is on , triac is in Off state , capacitor get a signal voltage through the Fan and resistor and this capacitor charged. When capacitor is fully charged, the capacitor stored power and Diac get turned On and Triac also turn on and supply passed through triac. As Triac turn ON Capacitor Discharged. Again Capacitor get current through resistor by passing the Load and input line and Charged. Capacitor Discharged by the giving the power to Diac and therefore again Triac turn on because Diac give a signal to gate terminal.
This Charging and Discharging of capacitor randomly occur and Triac turn ON-OF Randomly also. The Timing Rate of charging of capacitor is increased by the incresing of resistor value. So, Combination of Resistor and capacitor in this circuit make a timing delay.
A Protection circuit can included for Triac protection by the adding of resistor and a capacitor in series with the parallel of Triac . This ic called Snubber circuit, this is required only in inductive load like motor/fan. not for resistive load.
When we increased the timing of charging rate of capacitor then triac get 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 – In capacitive Regulator there are some capacitors connected in series with the load and each capacitor has a resistor in parallel. Capacitive Regulator are very popular and easily available in market. This is some costly than the triac based regulator. But the Result is better than Triac regulator.
The advantage of this regulator is there is no any noise humm sound produced by FAN. At Low speed low power consumption.