This article presents speed controlling for single phase induction motor. Principally, 9-level, diode-clamp inverter used to control voltages per frequency is widely used because of its high efficiency to control the motor. In this article, ARM7 model ADU7024 is used as microcontroller to generate eight pulse signals and send to the output voltage amplifier by co-connecting to the modulation module using IC 7408. The obtained output signals are combined to IOR 2130 to generate 15-volt output for driving each gate. The 9-level, diode-clamp is employed to control single-phase induction motor. Such method when was tested to 220-V, 1/3 Hp, 50 Hz motor shown that it could control the voltage per frequency properly. When using the 9-level, diode-clamp inverter controlled by modulation, the results shown that the output waveform were very similar to the sinusoidal wave comparing to the typical waveform, resulting to drive the load efficiently.