PLC connection

Transistor output PLC can provide you with the pulse output and the connection to the NPN type sensor. This type of PLC will allow you to control servo motor easily since it also allows you to receive pulse inputs to do the error counting.

in the PLC, you can see at the output side there are many ‘commons’ (COM). This is to give you freedom to connect to many type of outputs that is of different supply voltage.

The operation of the PLC system is simple and straightforward. The Process or CPU completes three processes: (1) scans, or reads, from the input devices (2) executes or “solves” the program logic, and (3) updates, or writes, to the output devices. http://plctutorial.blogspot.com

You can see many more useful information athere!

two stage counter

When an SV higher than 9999 is required, two counters can be combined as shown in the following example. In this case, two CNT instructions are combined to make a BCD counter with an SV of 20,000.

PLC ladder logic two stage counter

for more information, go to yourplctrainer.com

how plc works

Once the program is in the CPU – the PLC is then set to “run”, and the PLC executes the application program repeatedly. In addition to executing the program, the CPU regularly reads the status of the input devices, and sends data to the output devices. The Input system senses the status of the real world inputs (a switch, a level, etc.), translates them to values that can be used by the CPU, and writes those values to the Input table. The application program is executed, and writes values to the Output table. The Output system then converts the output value to a real world change (motor turns on, valve opens, etc.)

servo motor

it is very easy to do a positioning control using a servo motor with the PLC. all you need to do is to configure the correct settings of the PLC, construct a correct wiring and write the program. if you buy a servo motor with the driver, make sure you hv the correct wiring. what im providing here is purely from the plc side.

i will sum it up into 3 steps,

1: configure the correct settings in your PLC.

make sure your plc has pulse outputs! you need two pulse outputs for a single axis. pulse can be output from the plc either by CW/CCW mode or pulse + direction mode. this mode must be of the same mode you setup in your servo motor amplifier. make sure also u set the built in inputs for encoder feedback. this is a must so that u know how many pulses has the motor moved.

2: correct wiring.

u also need to output the servo RUN signal to on the motor and Reset signal to reset any alarm. just for extra information, not all alarms can be reset from the reset signal, for some alarms, u need to reboot the servo driver.

for the input to the PLC from the servo driver, u need the feedback from the AC servo motor encoder. if you are using open collector, one feedback input is enough. it will count the Z phase from the encoder and pass it back to the plc to do the pulse count.

u also can tap into the PLC the ‘pulse output complete’ signal from the servo driver. this is important to make sure all pulse have been supplied and the motor is ready for next move.

3. write the program.

you can have a look at the sample program and better explaination HERE!!

PLC automation

Automation plays an increasingly important role in the global economy and in daily experience. Engineers strive to combine automated devices with mathematical and organizational tools to create complex systems for a rapidly expanding range of applications and human activities.

Many roles for humans in industrial processes presently lie beyond the scope of automation. Human-level pattern recognition, language recognition, and language production ability are well beyond the capabilities of modern mechanical and computer systems. Tasks requiring subjective assessment or synthesis of complex sensory data, such as scents and sounds, as well as high-level tasks such as strategic planning, currently require human expertise. In many cases, the use of humans is more cost-effective than mechanical approaches even where automation of industrial tasks is possible.

Specialised hardened computers, referred to as programmable logic controllers (PLCs), are frequently used to synchronize the flow of inputs from (physical) sensor and events with the flow of outputs to actuators and events. This leads to precisely controlled actions that permit a tight control of almost any industrial process.

For more information and tutorials, this is a useful website for all of you. Click HERE!