Development of constant voltage control system for hot-melt pipe welding

According to international standards of hot-melt pipe welding and requirement that the amplitude fluctuation of output tunable voltage should be less than plusmn 0.5 V, a high performance hot-melt pipe welding control system was developed. Single chip microcomputer 89C51RD2 was the control core of the system. It analyzed the working principles of hot-melt welding system that by using interruption and timing technology, comparing A/D sampling feedback voltage with the output voltage and adjusting the conduction angle of thyristor to produce the adjustable high accuracy welding voltage. The results of test show that the system voltage can immediately obtain constant value. The amplitude fluctuation of output voltage in welding course is less than plusmn 0.1 V. It obtains design rating and meets the requirements of production.