Friday, March 23, 2012

Application Melsec PLC Ladder Logic in Discrete Input Multiplexing- Demultiplexing





This Note of Application is for making simpler and storing module of digital input. Every group of sensing device and pilot signaler with diodes assembled is linked to the module of digital input. And each group power common line is linked to the module of digital output and driven with sequential strobe. The digital output synchronizing strobe, every group of signaler will provide their data information to module of digital input and this will perform as multiplexing with Time Division Modulation (TDM). Or else in the PLC, digital output synchronizing strobe, data information of group of signaler from digital input module is saved in the shield memory one by one and this will operate as de-multiplexing.

Used Ladder Logics
The output from Y2C to Y2F is to output strobe sequentially for multiplexing, and a strobe is required per the multi-input group. The group of multi-input should include type of dry contact signaler such as Switch of Limit, Switch of Push-button, Switch of Thumb-wheel, semi-conductor type signaler similar to proximity switch is not appropriate for this application allowing for fast speed response.

The output of strobe should be coordinated to data train in the ladder logic. In the realistic example, At first PLC RUN scan start, DATA Train(MOV H7 K4M16) and Strobe train(MOV H2 K4M0) is synchronized. The meaning value of hexadecimal H2 and H7 is as below figure;


These train of data/strobe are moved by 1 bit when M9036 is scanned and terrified to general multi- input group power line. The information data of multi input set is acknowledge to inside coil group by action of "Safe in time" in the PLC. These results make simpler and storing module of digital input.

Example for Calculation Command Application.
• The module of Analog Input/Output
• DAI Analog Input Module Set-up A1S68AD/ A1S68DAV,
• Analog Input PV Scaling
• Threshold ON-OFF of Schmitt
• Hold of Peak Value
• Analog PV of On / Off Controller
• Clamping of Analog Value, Limitation
• Calculation Command Bit Shift
• Drive Speed Control of Analog
• SUM Finding Stable Value from Analog Input Hunting
• Control of Drive Multi stage by Feedback Encoder
• Material Mixing of Ratio Control
• Truck Loading of Trickle Control
• Single Counter of Rate Sampler
• X 0 Shifted Signal of Analog Scaling
• Y 0 Shifted Signal of Analog Scaling
• Proportional Non-Linear Curve of Piecewise
• Piecewise for Non-Linear Curve of Inverse Proportional
• Profiler Linear


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