Connectors
What is a Connector ?
A Connector connects Kelvin to various types of assets at the edge such as PLC, DCS, SCADA, HMI, Flow computers, etc. It supports numerous communication protocols making it a universal solution for industrial automation communication. Kelvin provides a number of out-of-the-box Connector solutions and clients can also build their own custom Connectors.
The Connector reads and writes data converting the asset's protocol and storage address into Kelvin's Asset / Data Stream pair format for the cloud database.
Deploying Connectors
When creating a new Connector, it will be deployed to the assigned Cluster. The Cluster will automatically assign the Connector to one of the Nodes in the Cluster.
If you are using an asset communication which requires direct connection to the asset such as serial communications, then you must use a single node Kubernetes cluster to guarantee the Connector is deployed to the correct hardware.
Data Stream Storage
Data from an Asset’s Data Streams can be stored locally or synced to the cloud.
When deploying a Connection, you can select the storage location per Data Stream. This enables granular control within a single Connection.
Node
By default the data will be stored both on the node and synced to the cloud.
Protocols
| Protocol | Description |
|---|---|
| OPC UA | OPC Unified Architecture (UA) framework for backwards compatibility and "future proofing" for future frameworks. |
| MQTT | Message Queue Telemetry Transport lightweight network protocol to transport messages between devices. |
| Modbus | One of the original industrial communications protocols developed in 1979. It has two transport layers RTU and TCP. |
| ROC | Emerson Remote Operations Controller protocol to communicate with Emerson controllers and FloBoss / RegFlo flow computers. |
| Custom | Written by clients to connect to their assets |
OPC UA
The OPC Unified Architecture (UA), released in 2008, is a platform independent service-oriented architecture that integrates all the functionality of the individual OPC Classic specifications into one extensible framework.
This multi-layered approach accomplishes the original design specification goals of:
- Functional equivalence: all COM OPC Classic specifications are mapped to UA
- Platform independence: from an embedded micro-controller to cloud-based infrastructure
- Secure: encryption, authentication, and auditing
- Extensible: ability to add new features without affecting existing applications
- Comprehensive information modeling: for defining complex information
The multi-layered architecture of OPC UA provides a "future proof" framework. Innovative technologies and methodologies such as new transport protocols, security algorithms, encoding standards, or application-services can be incorporated into OPC UA while maintaining backwards compatibility for existing products. UA products built today will work with the products of tomorrow.
The OPC UA information modeling framework turns data into information. With complete object-oriented capabilities, even the most complex multi-level structures can be modeled and extended.
This framework is THE fundamental element of OPC Unified Architecture. It defines the rules and base building blocks necessary to expose an information model with OPC UA. While OPC UA already defines several core models that can be applied in many industries, other organizations build their models upon them, exposing their more specific information with OPC UA.
MQTT
MQTT (Message Queue Telemetry Transport) is a lightweight network protocol to transport messages between devices. It uses a publish-subscribe architecture and usually runs over TCP/IP but can be used on many other communication protocols.
It has become a popular method to transfer continuous streams of data as it is very simple to implement and requires very low bandwidth. It also allows the clients who create information (publisher client) to be independent and not connected to clients who consume information (subscriber client).
The MQTT broker is the glue which manages the transfer of information between publishers and subscribers. MQTT clients will connect to the MQTT broker only.
Modbus RTU and TCP
Modbus is a data communications protocol originally published by Modicon (now Schneider Electric) in 1979 for use with its programmable logic controllers (PLCs). Modbus has become a de facto standard communication protocol and is now a commonly available means of connecting industrial electronic devices. It is now popular in industrial environments because it is openly published and royalty-free. It was developed for industrial application, is relatively easy to deploy and maintain compared to other standards, and places few restrictions - other than the datagram (packet) size - on the format of the data to be transmitted.
The Modbus protocol can use many types of transport layers. For Kelvin we support RTU serial communication and TCP Ethernet transport layers.
Modbus supports communication to and from multiple devices connected to the same cable or Ethernet network. For example, there can be a device that measures temperature and another device to measure humidity connected to the same cable, both communicating measurements to the same computer.
Modbus is often used to connect a plant/system supervisory computer with a remote terminal unit (RTU) in supervisory control and data acquisition (SCADA) systems in the electric power industry. Many of the data types are named from industrial control of factory devices, such as ladder logic because of its use in driving relays: A single physical output is called a coil, and a single physical input is called a discrete input or a contact.
The development and update of Modbus protocols have been managed by the Modbus Organization since April 2004, when Schneider Electric transferred rights to that organization. The Modbus Organization is an association of users and suppliers of Modbus-compliant devices that advocates for the continued use of the technology.[4] Modbus Organization, Inc. is a trade association for the promotion and development of Modbus protocol.
Emerson ROC
Emerson Remote Operations Controller combines the ruggedness and low power consumption of a RTU, the scalability, speed and control of a PLC, and the audit trails and historical data of a flow computer enabling you to measure, control and optimize your oil and gas operations using a single device.
You can communicate to the Emerson Remote Operations Controller (ROC), FloBoss, and RegFlo using the Emerson ROC or ROC plus protocol. It can be used to access and retrieve information from the database configuration, real-time clock, events, alarm logs, live data and historically archived data.
Communications over TCP / IP and serial (direct, radio, or dialup) links are supported.
Custom
Clients also have the ability to write their own Connectors. The Connectors are stored in the Kelvin App Repository where the Operations Engineers, Software Engineers or Administrators can create and deploy to the edge to connect the assets to Kelvin.