Add-On Instructions (or AOI for short) allow the programmer to create new specific and unique instruction types or complex functions for a company or OEM requiring commonly used logic.

The AOI will provide a common dialog to the end-user logic and include documentation for the instruction creat...

Some of the benefits of using AOIs are:
- Reuse of coding to promote consistency between projects by reusing commonly used control algorithms.
- Maintenance troubleshooting friendly for technicians to understand by providing an easier to understand interface for complicated algorithms inside of a...

Let’s begin to create a simple AOI that will convert Celsius to Fahrenheit and Kelvin temperature.

We will use all of the steps required in developing an AOI.
- The equation to convert Celsius to Fahrenheit is: (°C * 1.8) + 32
- The Equation to convert Celsius to Kelvin is: °C + 273.15
- The Eq...

1. Select “Create - New Project”.
2. Select “Studio 5000 Logix Emulate Controller” for the controller type. Call the program Name: “RealParsAOI”.
3. We use the “Studio 5000 Logix Emulate” software, a virtual PLC running on the PC, to download and run and test our AOI program. AOI development is...

We will create the “Input-Output” parameter tags.

- Let’s define an input tag as “Celsius”. Celsius will be configured as a REAL data type and as a Float style tag. The default value will be 0. The Required and Visibility column checkboxes will be checked because the tags are requiring an argume...

We will create three constants that will be used in our calculations. Let’s create “Constant_1”, “Constant_2”, and “Constant_3” as REAL data types and as Float style tags.

The default values will be respectively 1.8, 32, and 273.15.

The “Scan Modes” tab allows the designer to setup pre and post scan logic. We won’t be configuring these useful modes but will be explained.
- For the Prescan routine, the logic configured in this routine program is examined prior to the execution of the AOI. This allows for the AOI instruction a...

- The “Signature” tab allows the designer to prevent the AOI from modifications.
- The “Change History” tab displays the history of changes with names and dates and times.
- The “Help” tab will allow the user to create specific help text about the functions and logic used within the AOI.

Let’s create the internal logic used to perform the conversion.
In the logic window for ladder logic development, we have three instructions created for the logic to be used for the conversion.
- The first instruction is a “Compute” instruction allowing us to create the equation for a destinati...

Let’s use the AOI in ladder logic to see the results of the equations used in our AOI.
We will now go to the Instruction toolbar and select the Add-On
tab. We will select the RealPars icon from the toolbar.
The AOI will now be added to rung 0, but it still requires some configuration.
- First, l...

We’ve added a few more instructions to help with the simulation.
If you would like to follow along, the Studio file, named RealParsAOI
can be downloaded from this link: https://bit.ly/38pEFdT
- The TON or Timer On Delay instruction set for 5000 milliseconds or 5 seconds and will increment the C...