A distributed rectifier testing system based on RS-485

Focusing on the function shortage and low productivity of existing testing equipment in the semiconductor rectifier bridge manufacture procedure, we designed a master-slave structure testing system. In this system, a PC acts as host processor, and several distributing local single chip micro controllers(SCMs)act as slave processors. The SCMs mainly perform classification and testing each rectifier, and the PC performs data display, counting, storing, printing and other test functions. The communication between the principal and the subordinate machine uses RS485. The communication software at the host is written in VB6.0 based on the Windows operation system. We used MSComm's communication API in VB6.0 to access serial ports, and implemented data reception and transmission. In order to support long distance transmission outdoors, to increase anti-interference performance and to resist lightning storms, the voltage level convert between SCMs' TTL and RS-485 is performed by a SN75LBC184 chip which can be both anti-lightning and can bear 8kV static electricity shock. Applications showed that the newly designed system has the characteristics of reliability, obviously high working efficiency, and decreasing the rectifier bridge production cost.