Nov 24, 2017

Difference Between Reflective, Retro Reflective & Through beam Optical Sensor

Sensors are the very important part of automation industry and are categorized into many types, like proximity sensor, level sensor, pressure sensor, photosensor or optical sensor etc. We widely used these sensor in our industry for object detection, fault detection etc. Sensor are those sensing device which senses and convert that to the electrical signal. In this tutorial we will learn what is the basic difference between a reflective or diffused photo sensor, retro reflective & through beam Optical or photo sensor. Subscribe to Automation-Talk by Email.

Difference Between Reflective, Retro Reflective & Through beam Optical Sensor
Image source:

On seeing the above picture, you must have got an idea that what is the difference between these 3 types of optical sensor.

Through beam optical sensor has transmitter and receiver as a separate device and work on the principle that whenever a object comes between transmitter and receiver a signal is sent. Used when sensing distance is large.

Retro reflective type of optical sensor has transmitter and receiver on same housing and they require a reflective surface called reflector for there working.

Reflective optical sensor are also called diffused photo sensor and has transmitter and receiver on same housing but they do not require any reflector for there working. Object to detected itself work as a reflector.

The main advantage of optical sensor's is that they do not do the difference between the object, unlike proximity sensor.

Nov 7, 2017

Motor Related Common Electrical Terms - Part 2

In the last section we studied about some of the frequently used motor electrical parameters in our day to day work. We have already understood about the different types of AMPS rating that a motor nameplate have, in this post we will try to understand about the design of motor that is what type of torque and speed curve motor have, we will also look in to efficiency, frame size, and frequency. Subscribe to Automation-Talk by Email.

Motor Related Common Electrical Terms

What Does Design of AC Motor Indicates

There are generally four types of design A B C D that an AC Motor can have. The design of AC Motor just indicates the type of speed v/s torque curve that the motor will have. The speed v/s torque curve for all the designs of the motor is below.

The standard industrial motor will mostly have the design B, it has reasonable starting torque with average speed and starting current with a good performance. In the above curve, we see that design C has the high starting torque so this type of motor is used where we have to start the high loads. Design D is the so-called high slip motor which tends to have very high starting torque but has high slip RPM at full load torque. Design D motors are generally suited for press and elevator applications. Design A motors are not particularly specified but are used where the high pull out torque is required.

What does efficiency of AC Motor Means?

Efficiency is indicated on the nameplate of the motor and in simple terms, it means that it is the amount of input energy that is converted into work. We should always select a motor that has high efficiency.

Meaning of Frame Size in AC Motor

As everything in this world has some size, same is the case with the motors. As the motor HP increases or RPM decreased the frame size of the motor increases. NEMA (National Electrical Manufacturers Association) has prescribed standard shaft diameter for the particular frame size so as to maintain a standard among all the motor manufacturers in the world.

What does Motor Frequency Indicates

Frequency on the motor nameplate means that for which input frequency motor is designed to operate. Most common motors have operating frequency of either 50 or 60 Hz.

We have understood some of the more common electrical terms in this post. We will also cover other commonly used electrical motor parameters in the upcoming post. If u have any doubts at any point please feel free to write in the comment section.

Oct 30, 2017

How To Reduce Electromagnetic Interference in Servo Drives

Motion Controllers and Servo drives are used in machines for the better controlling and accurate positioning purpose. The one thing which we should keep in mind while installing the motion control panel is to have a safe and healthy environment for the Servo Drive and Motor operation i.e the environment should be free from any Electromagnetic Interference (EMI). EMI can dramatically reduce the performance of the system and can lead to various other problems. In this post, we will see that what practices should be followed in order to have the minimum or zero effect of EMI.

Reducing EMI effect by following Standard Wiring Practices

How To Reduce Electromagnetic Interference in Servo Drives

Generally, all major servo drive and motor manufacturers have their products following CE compliance. But using CE approved components will not guarantee a CE compliant System. The whole depends upon the components In drive, interconnection procedure, and installation method. So we should follow the practices by which the EMI effect can be minimized.

Electromagnetic Interference is generally generated by High frequency switching circuit. EMI generated inside the enclosure is either conducted or radiated back inside the enclosure only, so proper measures should be taken in order to avoid EMI conducted back into the main power source. Below picture illustrates that how EMI is conducted or Radiated back to the main power source.

EMI Radiation Conduction

Steps to Follow for Reducing/Minimizing Conducted EMI Effect

In order to reduce the Conducted High-Frequency noise, an EMI filter should be installed in series with the power supply. This EMI filter should block frequencies causing Interference and also not saturates at the current level required for normal operation. The EMI filter should be installed in such a way that it blocks EMI conduction to main power supply.

Shielded and Screened cables should be used wherever appropriate. Power Supply cables should be kept separate from Signal Cables and all cables should be as short as possible. Ground wires should have sufficient cross-section area in order to minimize the Skin Effect and conduct EMI to ground. Connect the EMI filter properly as shown below.

EMI Filter Correct Wiring

How to Remove the Radiated EMI Interference:-

Several points should be kept in mind to reduce the radiation of EMI back to the main power source. If there are any holes in the enclosure than the Holes should be as small as possible. Use conducting Gasket at seams of the door. Avoid grounding the Screens/Shield at only one end, doing this can dramatically increase the radiated EMI. If you found any particular cable is creating much EMI than it can be reduced by ferrite beads.

We will summarize the important points below:-

All cables that connect to motor control should be shielded. Input power cable and Motor Output cable should be separate and positioned independently. Grounding must be done properly and all cables should be laid close to the ground plane. The motor cable shield should be connected to a motor ground terminal at motor side.

Motor Correct Wiring Procedure

The above picture shows the standard wiring procedure for better efficiency.

The shield/screen of all cables connected to the control must be grounded to the control by connecting the shield to the control’s “Ground” terminal. The cables include the motor cable, input cables, feedback cables regen/dynamic resistor cables and other control cables.Subscribe to Automation-Talk by Email.

If you strictly follow all the steps told above, then definitely the EMI effect will be minimized and will achieve better efficiency and increased life of your product. In upcoming articles, we will further discuss the more advanced things to eliminate the EMI effect completely from your system. Till then you can subscribe to Automation-Talk by Email to get all latest updates by eMail.

Oct 9, 2017

PID Control with Auto Tuning in Omron PLC

PID control as we all know is a fundamental thing used in process automation. For PID control we generally use PID Controller, but in Omron PLC there is one exclusive instruction for PID purpose. This instruction is very helpful in many application where we can minimize cost by using software PID inside PLC. In this post, we will see that how to use this PID Instruction in Omron PLC.

PID Control Feature In Omron PLC

Omron PLA is very popular in the Automation industry and used in a wide range of applications. Omron PLC have exclusive feature that we can create a PID inside PLC by using an PLC Instruction. The name of PLC instruction is PIDAT.

Syntax:- PIDAT S C D

Where S is the Input word, C is the control/Parameter Word and D is the first output word.

When the input condition of this instruction is on then it performs the PID control on the bit in word S according to the control word C. The different bits of Control word C defines the PID process parameters. Let us see the meaning of each bit of control word C. The word C defines the target value of the process being controlled.

C+1 defines the proportional band i.e the parameter for P action expressing the pro­portional control range/total control range. C + 2 defines Tik Integral Constant, a constant expressing the strength of the integral action. As this value increases, the integral strength decreases. C+3 stands for Tdk Derivative Constant, constant expressing the strength of the deriva­tive action. As this value increases, the derivative strength decreases. C+4 stands for the sampling period, the sampling period can be designated in units of 10 ms (0.01 to 99.99 s), but the actual PID action is determined by a combination of the sampling period and the time of PID instruction execution (with each cycle).

Below is the diagram explaining PID action.

PID Control with Auto Tuning In Omron PLC

PID action combines proportional action (P), integral action (I), and derivative action (D). It produces superior control results even for control objects with dead time. It employs proportional action to provide smooth control without hunting, integral action to automatically correct any offset, and derivative action to speed up the response to disturbances.

This instruction is very useful for PID block creation. Dont forget to subscribe to get all latest updates. Subscribe to Automation-Talk by Email.

Aug 29, 2017

How To Find PPR and Maximum Frequency of Encoder

Encoder comes with a specified PPR i.e pulse per Revolution and Maximum Frequency output of the pulses given by encoder. Generally, encoders are mounted on the shaft of the conveyor, so according to the resulting RPM we should select the encoder with a proper PPR and output frequency.

How To Find PPR and Maximum Frequency of Encoder

How to Find PPR and Maximum Frequency of Encoder

The encoder is interfaced with the PLC for counting the pulses given by encoder and taking the feedback. PLC inputs also have a frequency range for the pulses which it can accept. So calculating the frequency of pules by the encoder is important in an application. Below is the formula to find the Max. The frequency of encoder in from the PPR and RPM.

Max. Frequency of encoder in Hz = (RPM / 60) * PPR

So if the encoder is mounted where the RPM = 2000 and PPR of the encoder is 360 the frequency of encoder will be 12KhZ. So we could find out that our PLC will be able to count pulses with this frequency or not.

Recommended Article: Using High Speed Counter in Omron PLC

Let us also see the difference between Single turn and Multi Turn encoders.

In single turn Encoder, the output code is repeated after every single revolution of the encoder shaft i.e we can not actually determine how many turns have encoder made 1 or 1000.

In Multi-turn Absolute encoders, the output is unique for each revolution or for every shaft positions up to 4096 revolutions and we can get to know that the numbers of rotation of Encoder.

For more updates on Encoders you can subscribe to get all information in yours Inbox. Subscribe to Automation-Talk by Email.

Apr 29, 2017

How To Set & Release Omron PLC Password

Every PLC has a feature to lock the program and Data Words inside the PLC, so that no one else can see and copy the program made by you. We do a hard job to make PLC Programs and thus also wants that no one else should take the credit of our hard work. In this article we will see "how to set and release the password in Omron PLC".

How to Put Password in Omron PLC

To set the password in Omron PLC like CPM2A, CP1E, CP1H etc., first make your program and after that in the left hand side project workspace is there. Right click on the PLC name and select Properties and Under protection tab you can set the PLC Password.

See below picture for a better Understanding.

Omron PLC Password

You can also Release the Password.

To release the password just Select PLC tab -- Protection and then click on Release password. Once you have set the password in Omron PLC for Program and memory data then no one can Upload the PLC program without knowing the password. Also, the password will always be saved in the program and you can see it if you forgot what password you have put.

Also check out the Step by step procedure for removing PLC Password.

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Feb 26, 2017

Increasing/Decreasing Speed using Buttons in JX Drive

In some of the application in industries, need of increasing and decreasing the speed using VFD drive through a single control panel using the push of Buttons is required. One of the best example of such machine is sheet laminating machine where operator can simply increase/decrease the speed using buttons. In Omron JX drive this function can be performed with ease through parameter of the drive. Here we are not talking of MODBUS communication and will use input from terminal. This feature can also be done using MODBUS communication and also with the help of POT. Subscribe to Automation-Talk by Email.

start stop control panel

Below are the important parameters which need to be set in Omron JX drive to use increasing and decreasing Speed feature using Buttons.

1. A001: Frequency reference selection:

In this parameter select 02 to use Digital operator as the input source for frequency. By default this is set to 00 (Digital Operator- Freq. Adjuster).

2. A002: Run Command Selection:

By default this is set to 02 for digital operator. Select 01 for terminal mode. By selecting this parameter, you will only able to give run command through control panel or terminal buttons.

3. C001: Multi-function input 1 selection: UP

This is the parameter which lets you use first input button, say Start button as increase button. By default this parameter value is set to 00 for Forward (FW). Change this value to 27 which will increase the frequency.

4. C002: Multi-function input 2 selection: DOWN

By default this parameter is set to 01 for reverse (REV) and we have to select 28 which will decrease the frequency. This feature is applicable while the machine is in RUN mode.

Notes the below points while using C001 and C002 parameters:

1. While the UP/DWN terminal is turned on, the acceleration/deceleration time depends on F002, F003/F202, and F203.

2. You can store a frequency set value after UP/DWN adjustment. Choose whether to store the value with C101.

3. Also, you can clear the stored frequency set value by allocating 29 (UDC) to the desired multifunction input and turning on/off the UDC terminal.

4. The UP/DOWN function is disabled when the JG operation is enabled.

5. The UP/DOWN function is enabled when the frequency reference selection (A001) is set to the Digital Operator (02).

6. The UP/DOWN function is enabled when the multi-step speed reference is enabled.

After setting the above parameter you can test this by using Start and Stop buttons. Use start button for increase and stop button for decrease. Now press and hold the increase button to increase the speed and release the button to hold the speed to that point and do same for decreasing the speed. If you have any issue in setting your button to UP and down mode (increase/decrease) then please let us know. To get the latest tutorial and program subscribe to Automation-Talk by Email.

Nov 7, 2016

PLC Programming For Counting Encoder Pulses

PLC Programming For Counting Encoder PulsesEncoder is mainly used for feedback purpose to know the position and distance measurement in Industrial applications. But before going in to the PLC Programming we should be familiar with Types of Encoder , Interfacing of Encoder with PLC.

PLC Programming For Counting Encoder Pulses / Feedback:-

Actually encoder is mounted on the shaft whose position we want to determine or want to monitor its value. Encoder have some PPR and they gives accordingly that number of pulses in one revolution.

Note:- The coupling of encoder with shaft should be done properly for accurate measurement otherwise the efficiency will decrease or it can even destroy.

PLC Logic Development:-

Now we will see the step by step detail for making the PLC Program. First of all we have to decide the condition that when should the counting start i.e when the pulses given by Encoder will be counted. Generally we want this at the auto-cycle start , So here we are considering at Auto Bit ok condition , however it can be done as per application requirement.

We here are considering the example of Omron PLC CP1H, in every PLC there is a Instruction for counting the high speed pules, In Omron it is PRV , so we will write PRV Instruction.

In PRV we have to define the port number where we have connected the Encoder and control Data. After that the value(encoder pulse value) will coming in one Data Register of PLC.

Now we have to decide as what to do this value. Let us take one example , suppose our encoder is of 360PPR i.e it will give 360 pulses in one revolution, Encoder is connected to motor shaft which is driving a conveyor and after every ever 300mm conveyor will stop and a cylinder will come down to cut.

So first we will calculate that in 1 revolution of encoder how much the conveyor moves.

If in 360 pulses conveyor moves 100 mm then we find that , for 1080 pulses of encoder conveyor moves 300mm.

Note:- Settings in the CX-Programmer.

So, after every 1080 pulses we will stop the motor and on the cylinder output and simultaneously reset the Encoder value, and continue this process. We will compare the Encoder Pulse value with the 1080 and at when they equal, motor stops, cylinder down and encoder value reset and motor again runs.

We have made the PLC Program accordingly. See the PLC Program below, we have included both the .cxp and .pdf files.

Download the PLC Program.

Also if you face any problem then you can leave us a comment. You can subscribe to get all related PLC Programs, SCADA Tutorials, HMI, VFD Installation related articles in yours inbox. Subscribe to Automation-Talk by Email for more such articles.

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