A microcontroller-based yarn twist tester

Twist is important parameter in specifying a yarn for many textile applications. A prominent textile industry currently employs obsolete yarn twist testers in its quality control laboratory to check yarn performance. However, the twist mechanism part is mostly intact. The purpose of the research is to restore and improve the function of the old yarn twist tester by replacing conventional control system with the microcontroller based - one. The newly designed tester is able to directly display the twist level and transmit the measurement data to PC via RS232 link. An application program on PC also provided to facilitate data analysis and storage. The system consists of main controller and twist mechanism. The primary task of the main controller is to control the twist mechanism to perform tpi measurement of the yarn sample. The MOSFET driver in H-bridge arrangement is employed to control the speed and direction of the motor using PWM method. The main controller also incorporates serial EEPROM and RTC to hold twist per inch (tpi) measurement data temporarily and to provide time stamp respectively. Interaction between user and the system is made possible matrix keypad and character LCD. The twist mechanism is used to perform untwist/twist action. It consists of a dc motor, a rotary encoder, a Hall-effect sensor, an opto - interrupter, and miscellaneous mechanical parts. Featuring 4 selectable speed setting, the final design has capability to measure number of twist of both Z- and S-twist yarn with error less than ± 1 tpi. Basic summary statistics provided by GUI includes number of sample, sample minimum, maximum, average, and standard deviation.