Eplex 2000 Programming

[Brian Scarano]

TheE-Plex 2000 electronic pushbutton lock eliminates the problems and costs associated with issuing, controlling and collecting keys. The locks traditional telephony style keypad and simple programming options provide convenient, cost efficient and durable access control.

E-Plex is the product name for E-Plex Limited's multiplexing technology. The name E-Plex collectively describes user interfaces, power distribution modules, machine interface modules, sensors and software, and the electronic protocol that allows data and power to be transmitted over the same wire. Simply put, E-Plex is a family of products that when deployed provide a complete system integration solution.

The number of wires required for different electronic protocols and networks can be confusing. Many vendors elect not to "count" the power wires while others do not "count" ground wires. This makes it difficult to compare apples to apples. E-Plex requires just two wires; a simple, non-shielded, twisted-pair. Power and data are transmitted across one of the wires while the second is the ground. No protocol can use fewer than two wires and most use several more. Using E-Plex dramatically reduces wiring connections (potential points of failure) and significantly reduces weight, cost and complexity.

E-Plex offers a number of unique attributes and is patented. Therefore, it is proprietary in the sense that it was not developed or maintained by a committee, like other protocols. However, the goal of E-Plex is to enable full system integration. Therefore, by definition, E-Plex must connect to and be connected with equipment of all varieties and as well as other protocols. E-Plex is a standard protocol that has been adopted across a number of industries. There are currently E-Plex interfaces available for products from Victron Energy, Dometic, a broad range of CAN products and more. E-Plex offers broader system integration options than alternative products and due to the focused effort applied to open integration, more components.

E-Plex is a master/slave architecture as compared to a message-based architecture. What this means is that a master module (called a Clock module) controls the timing of when modules on the network communicate their data. Thus there are no data collisions on the bus as well as dramatically reducing the messaging or "addressing" overhead required within data packets in a message-based protocol. This allows ample bandwidth on the bus to be achieved at a relatively slow baud rate. The result is more capability and functionality on the bus at a lower cost than message-based protocols.

No single protocol can perform all of data communication jobs that must be performed within any system, vehicle or piece of equipment optimally. As a result, a large number of multiplexing protocols have been developed and deployed to meet these specific needs. Generally speaking, protocols are "purpose-built." CAN was built as a message-based system for quickly communicating safety-critical data such as throttle position, airbag sensors or engine parameters. Most vehicles, for example, need this sort of data communicated and CAN is the correct choice; the right tool for the job.

E-Plex was built for a much broader, system-integration purpose. As such, E-Plex was designed to be very flexible. Rather than do just one job in a predefined way, E-Plex is logic-based allowing new features and functionality to be developed as needed for unique applications. There may be an overlap in functionality in some cases. However, optimal performance and the lowest possible cost is achieved by using E-Plex and CAN in a complementary manner.

E-Plex complements the various other protocols (CAN and others) at work within an application by bridging to them seamlessly and integrating their data to provide complete system integration. This is achieved via "bridge-modules" that allow data to flow back and forth. E-Plex has a wide array of these modules.

The maximum number of nodes/modules on the E-Plex, or any network, is a function of the length of the bus and the complexity or amount of data each node/module is communicating. Due to the use of the Clock module, nodes/modules typically communicate very small packets. Often just 1 bit small. With this size data-packet, E-Plex can support 2000 address points on the bus. Larger systems can be created by connecting smaller systems by the use of a bridge module.

An E-Plex network can be run 500 feet from the Clock (master module). However, the Clock supports a "star" configuration with multiple legs being run from the clock. Thus, when the Clock is centrally located on the bus, an E-Plex network can be as much as 1000 feet. Normal systems would be considerably smaller than this.

Unlike alternative approaches, E-Plex digital signals are not low-voltage and therefore not susceptible to electrical noise. E-Plex can operate from 10v-30v and uses full battery potential (usually 12v or 24v) to generate its digital signal. Because of this large signal, electrical noise induced onto the E-Plex bus can be easily distinguished from data signals.

There is a complex, but near-instantaneous, error-prevention process at work on an E-Plex network. On an E-Plex bus, data flow is initiated via the Clock. When the modules receive this command data is transmitted in an appropriate time-slice and the clock immediately echoes it back. The node then checks the data received back from the clock for errors. The Clock and nodes on the bus calculate a checksum of the entire packet and data is rejected and immediately resent if these checksums do not match. This process takes place 10 to 30 times per second.

If for any reason, a module on the E-Plex bus is removed, responding from the wrong location, or is sending an incomplete data packet, a data error is generated and displayed. At any time, an end-user can utilise the built-in diagnostics of the clock module to interrogate the network and further isolate the issue.

The end-user of any E-Plex system can access data and input control command via a number of user-interface and "switches". Great care has been taken to ensure redundant access to data and control points both for convenience and for system reliability. If one display or control point fails, the system will continue to operate and data can be monitored and control managed via alternative modules. Within the Clock module, a backup copy of all module software is maintained. If a module fails, a "blank" spare can be connected to the bus and the Clock immediately recognises it and downloads all required software. Many of the digital I/O modules also have manual override capabilities to allow operation of a mission critical channel in the unlikely loss of the E-Plex data communications network.

Like any network, or for that matter any electrical system, E-Plex depends on certain connections being maintained. As described previously, the E-Plex bus can be configured in a "star" pattern. This ensures that if one leg of the bus is severed, the rest of the bus functions intact. In the unlikely event of all legs of the bus being severed, key modules that manage AC & DC loads have manual overrides that allow "limp-home" capability. Such an interruption or even power failures/interruption do not have a residual impact on E-Plex. E-Plex is fully operational within just a few seconds of the bus being reconnected or powering-up.

E-Plex ability to distribute and switch DC and AC power is a key component to its overall functionality. DC distribution modules incorporate several levels of safety and security functionality. Over-current protection is provided via MOSFET-based technology that can be programmed to provide precise protection. Short-circuit protection is also incorporated and manual overrides allow DC loads to be switched even if a full system failure occurs, ensuring "limp home" capability. Patent-pending, board-level circuit interrupters unique to the E-Plex product line have been designed and deployed to add supplemental fail-safe protection. For AC distribution and switching over-current protection and short-circuit protection is provided by robust hydraulic-magnetic circuit breakers. The E-Plex Distribution Module for AC (DMAC) is a hybrid offering the advantages of "networked" power distribution and remote switching with the traditional electro-mechanical protection historically supplied via circuit breakers.

The term plug and play can be defined variously, but is generally used to describe the ability to add modules to a bus at will and the interoperability of modules is automatic. Due to its cost and performance benefits, E-Plex utilises a master/slave architecture. This architecture does require that the master module (i.e., the Clock) have a master copy of each modules programming. This means that new module can be added to bus but that an update to the Clock is required. The Clock has been designed for easy, front-panel access for such updates. However, E-Plex allows future functionality and modules to be programmed into the Clock. These option module features lay dormant until that module is introduced onto the clock. Once the module is added, the programming is downloaded to the module and it becomes an active part of the system. This approach actually redefines the term plug and play in a very important way. Because the Clock retains a master-copy of all programming, spare modules can be common across a wide array of equipment dramatically reducing part numbers and inventory within the service channel.

E-Plex was developed in the mid-1990s to meet the need for a low-cost, flexible protocol for system integration of complex equipment. E-Plex was initially deployed in large nuclear and turbine power plants and is currently at work in locations in North America, Europe, Asia and the Middle East. The technology crossed into numerous others industries starting in the late 1990s and is currently in production with high-end and production boat builders, conversion and production motor coach/RV manufacturers, and other diverse applications. For the last decade E-Plex has proven robust and reliable in a wide range of markets and applications.

3a8082e126