Fan speed controller ∼220 V on an asynchronous motor

Regulation of the frequency of revolutions of electric motors – common problem. Usually, brushed motor control circuits are relatively simple, and asynchronous motors require more complex solutions. We offer a device, ideal for fan speed control in bathrooms and offices, driven by asynchronous motors.

fan speed controller 220 V on an asynchronous motor

fan speed controller 220 V on an asynchronous motor

The circuit uses a specialized integrated circuit such as U2008B. The controller is designed for small single phase motors – it is not suitable for driving DC brushed motors and asynchronous three-phase motors.

Feature devices:

  • load: to 300 W
  • drive - triac
  • smooth control of rotation speed
  • smooth regulation of the minimum effective voltage
  • nutrition 220 VAC

circuit Description

The fan control controller is built on the U2008B microcircuit. Capacitor C2 is responsible for the so-called soft start, thanks to which there will be no voltage surge on the load when the regulator is connected to the network. Elements D1 and R1 rectify the voltage (half-life) and limit it to the value, safe for an integrated circuit, and capacitor C1 smooths this value. Elements R3 and R5 and potentiometer P1 are voltage dividers, used to set the required value.

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By using resistor R2, directly connected to the phase wire, internal synchronization blocks U1 control the activation of the triac synchronously with the supply voltage waveform. This largely minimizes radio interference., which can occur when pulsed switching of large inductances, which is typical for electric motor windings, at high supply voltages. In this way, no need to screen the circuit, and no need to use surge protectors. Generated noise level is much lower, than when using a standard switching power supply.


System installation is not complicated, but the circuit is powered directly from the mains, therefore it is recommended, so that the device is assembled without errors. When assembling, pay attention only to the correct polarity of the elements..

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After assembly, connect the load and set the potentiometers P1 and P2 according to your needs. Potentiometer P1 is used for stepless speed control, and P2 sets the starting angle, that is, the minimum effective stress across the load. Any adjustments should be made with insulated tools..

The assembled device must be installed in the case and make sure, that all protruding parts are securely fastened.

On the picture 3 shows the simplest way to connect the regulator to the load.

fan speed controller 220 V on an asynchronous motor

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The circuit is also suitable for driving AC brushed motors, however, in this case, you can abandon the resistor R7 and the choke L1.

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