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Click Click PLUS Communication EasyPLC Machine Simulator Modbus TCP Modbus TCP PLC PLC Learning

Click PLC EasyPLC Warehouse Stacker Example

The Machine Simulator (MS) is part of the EasyPLC software suite. It has many built-in machines that are used to show different programming techniques. The warehouse stacker example is one of these machines. Pallets are loaded and unloaded into the stacker machine. A maximum of 30 pallets can be stored. The stacker will work as a FIFO (First In First Out) device. This means that the pallets are stored in a sequence and retrieved in a sequence.
Click PLC EasyPLC Warehouse Stacker OperationThe Click PLC will be used to program this virtual 3D stacker machine. Indirect addressing (pointers) will be used to track the positions on the stacker to store and retrieve the pallets. Using the Click Plus PLC, we will connect to the warehouse stacking machine. This will be done using Modbus TCP (Ethernet) for communications. Using the five steps for program development we will show how this FIFO is programmed. Let’s get started.

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Do-More Do-More Designer PLC PLC Basics PLC Learning

How to Make a One-Shot in the PLC

A one-shot in the PLC will turn an output on for one scan. This is used to trigger events that should only happen once. An example of this would be to increment a value in memory. If a one-shot is not used, then every scan of the PLC will increment the value.


What is a one-shot in the PLC?

One-shots are known by several other names. Differential Up (DIFU), Differential Down (DIFD), One Shot Relay (OSR), Powerflow Modifier, Leading edge contact, Trailing edge contact, etc. This all relates to the programmable controller that you are programming.

PLC Examples of One-Shots

Let’s take a look at programming a one-shot using bit logic only. We will program both a leading edge one shot and a trailing edge one-shot bit. This program will work in all PLCs.
Note: The white background in the increment (INC) instruction just indicates the reset for the animation.

How to Make a One-Shot in the PLC

Leading Edge One-Shot Bit Example

Leading-edge one-shot bit: This will turn on a bit for one scan when the input condition makes a transition from 0 to 1. (Off to on)
When input X0 turns on C0 is turned on for one scan. This is because it is in series with the C1 lead work bit. The next rung will latch this on and not unlatch it until the input condition X0 turns off. C0 will only be on for one scan when X0 turns on.

How to Make a One-Shot in the PLC

Trailing-Edge One-Shot Bit Example

Trailing edge one-shot bit: This will turn on a bit for one scan when the input condition makes a transition from 1 to 0. (On to off)
When input X0 turns off C2 is turned on for one scan. This is because it is in series with the C3 trail work bit. The next rung will latch this on and not unlatch it until the input condition X0 turns off.

The Do-more PLC has several different ways to do the leading and trailing edge one-shots. Here is a couple:

How to Make a One-Shot in the PLC

The leading or trailing edge contact instruction will allow logic flow for one scan from a transition. (On to off / Off to on)

How to Make a One-Shot in the PLC

The leading and trailing edge Powerflow Modifier is placed before the output. It will turn multiple input signals into a one-shot for the output.

Watch on YouTube: How to Make a One-Shot in the PLC

If you have any questions or need further information please contact me.
Thank you,
Garry



If you’re like most of my readers, you’re committed to learning about technology. Numbering systems used in PLCs are not difficult to learn and understand. We will walk through the numbering systems used in PLCs. This includes Bits, Decimal, Hexadecimal, ASCII, and Floating Point.

To get this free article, subscribe to my free email newsletter.


Use the information to inform other people how numbering systems work. Sign up now.

The ‘Robust Data Logging for Free’ eBook is also available as a free download. The link is included when you subscribe to ACC Automation.


Categories
Do-More Do-More Designer PLC PLC Basics PLC Learning

Creating a Flip Flop Circuit in the PLC

A flip-flop circuit in a PLC usually has one input and two outputs. When the input is activated, the two outputs latch on/off opposite to each other alternately.  Basically, it is used to toggle (latch) an output on and off with just one input. In the PLC it is a single input that will toggle an output on and off each time the input signal is activated.


Flip Flop Circuit using Relays

Here is an example of a hard-wired flip-flop circuit using relays.
Creating a Flip Flop Circuit in the PLC

PLC Flip Flop Circuit Example

The PLC program will be a little different than the relays because of the way in which the PLC scans. Scanning takes place from left to right, top to bottom. The output conditions from the logic are available to the next rung as the logic is solved. Outputs and inputs are read usually only once at the end of the scan. Remember to think of the outputs in the PLC as make before break. This is the opposite of the relay logic presented above which is break before make.

Let’s look at the logic. This is programmed using the Do-More Programming Software which comes with a simulator. This full programming package is free of charge and can be downloaded here.

Creating a Flip Flop Circuit in the PLC

The input is on leading-edge instruction. (One Scan) If output 2 is on then it will set output 1. If output 2 is not on then it will reset output 1. The third line of code will determine the state of output 2 based upon output 1.

You may be asking yourself why do we not just use the conditions from output 1 to control output 1.  This is because if we substituted output 1 for the conditions on the input then output 1 would never turn on/off. The output conditions are available for the next line of the PLC code. This would allow the output to be set and reset within the scan without being updated. Using output 2 is the only way in which this logic would work.

Running the PLC Logic for the Flip Flop Circuit

Here is an automated picture to show the input toggling on / off and the outputs flip-flopping.

Creating a Flip Flop Circuit in the PLC

Note: An emergency condition can be added to the set or reset rungs to automatically control the output either way.

Watch on YouTube: Creating a Flip Flop Circuit in the PLC

If you have any questions or need further information please contact me.
Thank you,
Garry



If you’re like most of my readers, you’re committed to learning about technology. Numbering systems used in PLCs are not difficult to learn and understand. We will walk through the numbering systems used in PLCs. This includes Bits, Decimal, Hexadecimal, ASCII, and Floating Point.

To get this free article, subscribe to my free email newsletter.


Use the information to inform other people how numbering systems work. Sign up now.

Creating a Flip Flop Circuit in the PLC

The ‘Robust Data Logging for Free’ eBook is also available as a free download. The link is included when you subscribe to ACC Automation.