Categories
BRX Do-More Communication Modbus TCP PLC PLC Basics PLC Learning Scan

BRX Do-More PLC to Stride Field IO Modbus TCP

We will now look at the BRX Do-More PLC Modbus TCP remote io using Stride Field io. The BRX Do-More PLC can use remote inputs and outputs from Stride. The Stride Field I/O Modules are simple and compact. They provide an economical means to connect inputs and outputs to an Ethernet Modbus TCP communication network. Every module operates as a standalone Modbus TCP server and can be configured via a built-in web server.
Previously we looked at the Stride Field Remote IO Modules Modbus TCP Ethernet wiring and configuration.
Stride Field Remote IO Modules Modbus TCP Ethernet
Unboxing SIO MB12CDR and SIO MB04ADS Video
Powering and Configuring Video
We will be connecting two Stride remote inputs and outputs to the BRX Do-More PLC. Modbus TCP will be the protocol over Ethernet to communicate to the SIO-MB12CDR and SIO-MB04ADS units.
BRX Do-More PLC Modbus Remote IO
SIO-MB12CDR
– STRIDE discrete combo module, Input: 8-point, 12-24 VDC, sinking, Output: 4-point, relay, (4) Form C (SPDT) relays, 2A/point, (1) Ethernet (RJ45) port(s), Modbus TCP server.
SIO-MB04ADS
– STRIDE analog input module, 4-channel, current/voltage, 16-bit, isolated, input current signal range(s) of +/- 20 mA, input voltage signal range(s) of +/- 10 VDC, (1) Ethernet (RJ45) port(s), Modbus TCP server.
We will be reading an analog voltage into the BRX Do-More PLC from the remote IO unit. We will then set an output to pulse on and off at a time range indicated by this analog signal. The output will be on the other remote IO unit and will trigger the input to signal. We will look at the Frequency, Count, and Status of this input. Our BRX Do-More PLC program will also take into consideration watchdog (communication time out) and power-up events for the Stride remote input and output units.
Let’s get started.

Categories
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.