The RV-C protocol will use twisted-pair copper cable and has yet to specify a connector style for use in recreation vehicles’ internal networks.
BY CHRISTOPHER FRIESEN, CET
The recreational vehicle (RV) market is growing. Recent survey results show shipments of campers and motor homes, from manufacturer to dealer, at a 27-year high, with more than 384,000 products shipped last year. Other indicators support this data; in 2004, the term “RV” was the most searched term on eBay. And the future also looks bright, with projections for 2010 of an 8% growth in American households that own an RV.
What does this mean for the connector and cable industry? It means, pay attention to this strong niche market with its growing opportunities.
RVs yesterday, today, tomorrow
Traditionally “low tech,” RVs and the RV industry have remained largely unchanged for many years. Certainly, the look and feel has changed with the times, and new materials and processes have created innovations in the structure and durability of campers and motor homes. But technologically, they have lagged.
In the last few years, however, the industry has made impressive strides. Many RVs are specified, from factory, with solar power systems, onboard generators, and DC-to-AC inverters that let them function on- or off-grid for various lengths of time.
Given the power requirements for running a “home on wheels,” RVs and RV component suppliers are already a strong market for the connector industry. And now, according to David Bailey, the head of marketing and technology for Automated Engineering Corp., a supplier to the RV market, the RV industry is poised to take one of the largest technological leaps in its history with adoption of the RV-C networking protocol.
“The RV-C standard is a major technology advancement for the RV industry,” he says. “It is an open standard that will provide direction for all suppliers and manufacturers in order to produce products that will work together. The RV-C will provide lower-cost RVs with greatly increased reliability, functionality, and convenience for the users.”
Kent Perkins, director of standards for the Recreational Vehicle Industry Association (RVIA), agrees that RV-C will benefit the industry and its suppliers because it will “provide a minimum protocol for communication among installed components, including criteria for physical, network, and application layers.”
Martin Perlot, president of SilverLeaf Electronics Inc., a supplier of RV-C-compatible products to the industry, believes the standard will drive innovation within the industry: “RV-C is allowing designers to add new intelligence and features to their products. RV-C-enabled products can cooperate with other coach components; this will make many improvements in...our RVs.”
These industry experts agree that RV-C will help lower costs by providing on-board diagnostics, helping to reduce redundancy and overlap in existing RV systems, and providing modularity for easy aftermarket component installation.
Not quite ready to roll?
RV-C is being developed by the RVIA, and while the draft of the standard is complete, Perkins cautions that there is still much to be done.
“Currently, RVIA is working with the CAN [controller area network] in Automation [CiA] in order to get this document ISO/IEC-accredited, and this process is about a year from being completed,” Perkins says.
Even so, the RV industry is moving forward and looking for the connector system that will be used on every RV-C-compatible device. Someday, that will include every appliance and electronic component inside the RV, which today includes the power devices already mentioned, as well as roof-mounted or central air conditioners, furnaces, holding-tank monitoring systems, and entertainment system components like automatic stationary and in-motion satellite dishes.
Anatomy of RV-C
The RVIA’s ad hoc RV-C connector committee recently released a primer that outlined the physical layer for the RV-C protocol. RV-C is a CAN networking protocol, based on the automotive industry’s SAE J1939, and similar protocols from the boating and industrial automation industry verticals. It will be used by component and appliance suppliers to let RV manufacturers multiplex all devices.
“Networking provides communications that increase convenience and reliability by coordinating all components in a system,” the primer states in its conclusion.
As a CAN protocol, RV-C will use an unshielded twisted-pair cable to physically link each device. The draft protocol outlines the characteristics of the cable as copper, with the main trunk 18 to 24 AWG, and dropping to individual components sized 22 to 24 AWG. The characteristic impedance range for RV-C cable is 95 to 140 W, with a maximum propagation delay of 5 ns/m. The protocol also states: “Each end of the bus shall be terminated with a 120-W resistor.”
Other aspects of the RV-C bus include wire color-coding, with the preferred being CAN_H: White and CAN_L: Blue, and allowing for alternates Yellow and Green and White and Black, respectively. In the absence of proper color-coding, all RV-C network bus cables will need appropriate marking and must be built with 25 to 35 twists per meter.
But with all these specifics in place, several unanswered questions remain:
- What is the best routing, through the RV, for the backbone of the RV-C bus?
- How can the backbone be built robust enough to maintain network integrity in the long term?
- Should power and ground be provided in network drops to supply displays and other similar low-current devices with power?
- What type of connector or connectors should be used to interface the RV-C bus with all the components that will require access to the network?
Connector requirements
The industry is in the process of answering those questions, and recently sent a survey to RV manufacturers and other interested parties seeking guidance. Respondents were asked to rank the importance of the RV-C connector’s environmental ingress protection and operating temperature range, and to recommend specific manufacturers and connector models.
The response was small, with only 13 surveys returned-six from suppliers and seven from RV manufacturers. But the RVIA’s Perkins is confident the response was enough: “The survey was very helpful in further clarifying this complex issue; however, because there are so many options and variables involved with connectors, the technical subcommittee is still working on the actual language to address connectors within the RV-C protocol.”
Automated Engineering Corp.’s Bailey agrees: “We did receive the necessary information from the surveys to help direct the technical subcommittee to recommend a connector approach.”
While that process takes place, suppliers have two options:
- Slow down and wait until a standard connector emerges before finishing development of the RV-C products;
- Press on and risk selecting the wrong connector.
That risk may be minimized if SilverLeaf’s Perlot is correct about the approach he believes the technical subcommittee will take. Perlot believes there will be an array of suitable connectors from which designers will be able to choose.
“I don’t believe there will ever be a single standard RV-C connector,” he says. “Different products have different requirements for sealing, amperage draw, strain relief, and mounting, so there is no one-size-fits-all connector. Instead, I expect the committee will settle on standardizing the pin configurations for a selection of connectors. With such a list, a supplier would be able to select a connector appropriate for the product, but would be expected to use specific pins on that connector for power, ground, and the two data lines.”
The road ahead
The RV industry has a strong history of success, and an even stronger outlook for the future. The adoption of RV-C indicates that the industry is willing and ready to progress further technologically, and its commitment to technological advancement is seen as beging significant motivation for the connector industry to get involved.
By responding now, it is hoped that connector manufacturers can help the RV industry advance and reduce costs while improving its technology-based products.
CHRISTOPHER FRIESEN, CET is a freelance writer who frequently contributes to RV Technician magazine.
