The topic of this bachelors thesis is the speed control of a single-phase asynchronous motor by changing the stator voltage using Arduino development board and a triac. In this thesis, a singlephase asynchronous motor is used. The main part of this assembly is the Arduino board through which the user regulates the rotation speed. In addition to the Arduino, the circuit consists of two parts: a circuit for detecting the passage of stator voltage through zero and a circuit for regulating the RMS value of the stator voltage. A circuit for regulating the RMS value of a voltage is based on a triac, a semiconductor element which conducts when the current is applied to the control electrode. The triac is connected in series with a motor and he is controlled by the electrical impulses sent from the microcontroller. The circuit for detecting the passage of the input voltage through zero is required for accurate control of the ignition angle of the triac, i.e. for precise reduction of the stator voltage RMS value. The zero value of the voltage serves as a reference point for the time delay on the motor. The logic level of one of the Arduino IO pins alternates as the polarity of the input AC voltage changes, where the optoisolator serves as a connection between the AC supply voltage and the Arduino development board.