February 1, 2009
Input comparison instructions compare two values (constants and/or the contents
of specified words) and create an ON execution condition when the
comparison condition is true. Input comparison instructions are available to
compare signed or unsigned data of one-word or double length data.
PLC input comparison
The input comparison instruction compares S1 and S2 as signed or unsigned values and creates an ON execution condition when the comparison condition is true. Unlike instructions such as CMP (Compare) and CMPL (Compare Long), the result of an input comparison instruction is reflected directly as an execution condition, so it is not necessary to access the result of the comparison through an Arithmetic Flag and the program is simpler and faster.
The input comparison instructions are treated just like the LD, AND, and OR instructions to control the execution of subsequent instructions.
PLC input comparison
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December 14, 2008
The following program examples show two ways to create long-term timers
with standard TIM and CNT instructions.
Two TIM Instructions
In this example, two TIM instructions are combined to make a 30-minute
TIM and CNT Instructions
In this example, a TIM instruction and a CNT instruction are combined to make a 500-second timer.TIM 0001 generates a pulse every 5 s and CNT 0002 counts these pulses. The set value for this combination is the timer interval × counter SV. In this case, the timer SV would be 5 s x 100 = 500 s. With this combination, thelong-term timer’s PV is actually the PV of a counter, which is maintained through power interruptions.
PLC timer ladder logic 1
for more information, go to yourplctrainer.com
November 4, 2008
i have been asked about the connection from PLC to servo driver. The connection is not as hard as you would have been imagined.
First thing that is important in doing the wiring is that we need to identify the power requirements of our PLC, our inputs and our outputs. Please take note that some PLCs are powered by AC power and transistor output PLCs are powered by DC power. As for the case of PLC that have pulse outputs, it is powered by DC power ( i dont know any of AC).
The basic wiring from PLC to servo driver is as the diagram below,
plc to servo connection
For more information, go to yourplctrainer.com
September 20, 2008
This is a sample PLC programming that you can try.
A straightforward ladder logic using just the basic instructions to move the pneumatics actuator back and forth.
Click HERE to get the sample!
September 10, 2008
This website will give you PLC open source for the latest PLC programming projects. It covers the new PLC technology with the aim to educate people on a good PLC programming style that ensures easy troubleshooting and maintenance. Free tutorials and guides with an easy-to-understand example are provided.
This website also covers the hardwiring aspect of PLC. Real examples are taken as case study to make the learning process even more effective.