Abstract: This paper introduces the modification of the winding speed control device of a calender. The original dedicated integrated chip HEF4752 for the voltage-to-frequency converter and pulse width modulator (PWM wave generator) in the speed control device was replaced with an 87C196MC microcontroller. The SPWM wave pulse width was determined using the median sampling method, and the control software was programmed using a modular design approach. Practical application shows that the modified speed control device operates stably and reliably, saving 150 kWh of electricity per day compared to the original equipment. Keywords: Calender; Frequency converter; Microcontroller; Speed ​​control In the frequency conversion speed control device of a calender production line, the high-power transistor (GTR) is the core component, and general circuit protection measures are designed around it. Many frequency conversion speed control devices use the HEF4752 dedicated integrated chip to control the winding speed of the cord calender. The GTR is a current-controlled element; after injecting current J at the base, the collector receives an amplified current I, which is determined by the inherent amplification factor of the GTR. GTRs have two operating modes: switching and linear. In the switching mode of the variable frequency speed control device, the forward conduction current I and reverse blocking voltage U of the GTR are crucial parameters. Generally, these are selected with a margin of safety. However, in summer and when the mains voltage is unstable, the GTR and drive module are prone to burnout, mainly because the original device cannot withstand multiple surges. Adding an R-DC buffer circuit can mitigate some surges and reduce the power burden on components during switching operation, but it cannot completely eliminate the fault. With the maturity of intelligent high-speed switching components and products, and considering the problems encountered in actual production lines, this work modifies the original variable frequency speed control device by leveraging the advantages of microcontrollers such as small size, flexibility, reliability, and good performance-price ratio. The original voltage-to-frequency converter and pulse width modulator (PWM wave generator) integrated chip HEF4752 are replaced with a microcontroller, making the working circuit structure simpler and the control and maintenance more convenient. [b][align=center]For details, please click: Modification of Coiling Speed ​​Control Device for Calender[/align][/b]