Monday, December 26, 2011

PLC Control Unit of Panasonic FPX-C30T





A system of PLC, Panasonic FPX-C30T, is used to control the PIII processes and power supply. PLC possesses controlling functions for example sequencing, logic, counting, timing, etc. The PLC unit is supposed to control the processes of PIII. The PLC-based driving circuit. Deliver the pulse to manage grids G1 and G2. Nevertheless, the ports of I/O the Panasonic FPX-C30T can produce a pulse with a changeable frequency but only a set duty cycle or a pulse by a cycle of variable duty but a unchanging frequency. It is hard for the PLC to produce a pulse with randomly changing frequencies and pulse widths. In sequence to resolve this problem, a circuit of peripheral based on PLC is planned to get the driving pulse needed by PIII.

One of the ports of PLC I/O sends a pulse by a 20% duty circle and an randomly adjustable frequency between 10 - 1000 Hz. This pulse is interruption to produce a new synchronous pulse with a 320 μs width and consequently updated into a wave of saw tooth by an incorporated circuit. The wave of saw tooth is leveled by the signal DC from the module Times New Roman D/A of the PLC to generate a wave Times New Roman square as the novel driving pulse source. The pulse can be utilized as the signal of driving to change the IGBT after optical amplification and isolation. The frequency and length of the pulse can be precisely managed by the PLC. This system according to PLC can carry frequencies from 10 -1000 Hz and pulses with ranging widths from 10 - 300 μsecs with a maximum 1% duty circle.

The plasma load is usually reliant of the density plasma, gas pressure, specimen materials, etc during PIII. Consequently, the voltage of output pulse may adjust because of different plasma resistances, directing to variations in the energy implantation. A closed-loop control-system based PLC unit is built up and used in the power modulator. The control signal will be sent to change the DC high-voltage unit to guarantee a stable output voltage when the voltage noticed by the changes of PLC. Display the voltage and typical current on the different load condition resistances with and without constant voltage control. Obviously, the voltage output reduces with a lesser plasma load, which is not supposed in realistic applications.

The WEINVIEW MT510TV5 touch screen is employed as the user interface. Communication between the PLC unit and touch screen is kept through a port of RS-232. All the parameters are locate on the interface, and both procedure and manual modes are offered.


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