Trailers, ABS and Electricity: Getting Power Without the Blues

"AS OF THIS WEEK, the blue circuit is gone," a speaker said at The Maintenance Council's winter meeting March 3.

He was referring to the fact that trailer customers no longer can use the blue auxiliary circuit exclusively to power trailer-mounted equipment. That circuit on the J560 connector must provide fulltime power to the antilock brake system (ABS) that is required for truck trailers built after March 1.

Informal discussions with trailer manufacturers indicate that the industry geared up for the federal ABS mandate without significant difficulty. However, one significant question remains-the same question that has plagued trailer manufacturers, suppliers, and customers ever since the National Highway Traffic Safety Administration (NHTSA) proposed bringing back antilock brakes on trailers. How can the tractor supply the trailer with the power and the increased number of circuits required and still use the same connector that has been an industry standard for decades?

The industry is under pressure to have a proven method in place for detecting a malfunction of the trailer ABS and warning the driver with an ABS malfunction lamp in the cab of the tractor. NHTSA has set a March 1, 2001, deadline for an in-cab warning lamp. Meanwhile, fleets want to evaluate such a system with at least two winters of road testing.

What do trailer operators want from a tractor-trailer communications system? The week that ABS became mandatory on trailers, the TMC board issued a paper outlining its position. Although the organization is not recommending a particular manufacturer or system, it does want some specific things. Among them:

The signal for the ABS malfunction lamp must travel through a pin in the J560 connector.

It must work for trailers and converter dollies.

The signal must be standardized irrespective of individual manufacturer.

Components must be available from more than one manufacturer.

Systems should be ready for evaluation by June to provide ample time for testing prior to the 2001 deadline.

Available Options One of the TMC sessions showcased four different options of tractor-trailer communication, all of which are designed to meet the NHTSA mandate of a cab-mounted ABS malfunction lamp.

Truck-Lite Co Inc presented information on its SmarTechnology spread-spectrum communication system that has been in use for approximately two years. The fleets that have tested the system report no problems, said Brad Van Riper, vice-president of Truck-Lite. SmarTechnology uses either CEBus or J1708/J1587 communications architecture.

SmarTechnology uses chip sets and proprietary software to provide two-way communication between the tractor and trailer. The chips can be installed in a separate box or can be integrated into the electronic control unit of the ABS. Responding to questions about the proprietary system, Van Riper explained that the company plans to license the technology. "We plan to offer a license to anyone who is interested in gaining access to our copyrighted and patent-pending technology," he said.

The transceiver chips are manufactured by Intellon Corporation and Domosys. The microprocessor chips are available from at least three sources, Van Riper said. The system does not have to rely on the blue circuit. Any pin providing constant power will enable tractors and trailers to communicate bidirectionally using SmarTechnology.

PLC4TRUCKS Power Line Carrier For Trucks (PLC4TRUCKS) is another system for communicating between tractor and trailer using the J560 connector. It is being developed jointly by Freightliner Corporation, Wabash National, Meritor-WABCO, Cummins Engine, AlliedSignal Truck Brake Systems, Parasoft Computing Solutions, Vansco, Eaton Corp, Midland-Grau, Dialight, Federal-Mogul, Phillips Industries, Qualcomm Inc, Kysor Medallion, Thermo King, Highway Master, Air-Weigh, Vehicle Monitor Corporation, and Intellon Corporation.

PLC4TRUCKS can be installed in any electronic control, according to Ramin Younessi with Freightliner's chassis electronics department. Geared to accommodate a wide range of current and future trailer electrical needs, PLC4TRUCKS supports the SAE J1587 protocol. It provides a separate power line carrier network of up to 32 nodes-a far cry from simply illuminating a warning light in the cab of the tractor.

Younessi said the system resists the electronic noise produced by a wide range of sources, including chassis ground through the kingpin, PWM dimmer controls, fluorescent light controls, motors, AC inverters, and daytime running lights. The system supports existing electronics on tractors and trailers, including engine controls, ABS, electronic instrumentation, communications equipment, data recorders, airbags, and lube oil controls.

PLC4TRUCKS meets the requirements of TMC's RP144. Among them are: the in-cab lamp, the lamp check function, and the ability to comply with SAE J1455. It does not require new protocol, and it can coexist with J1587/J1939. Its open architecture does not involve licensing, and no patents are pending, Younessi reported.

PLC4TRUCKS began its demonstration phase January 21. Integrated circuits are scheduled for production and testing this spring, with vehicle testing planned this summer.

Air-Weigh System WireLink was the third communications system presented. Developed by Air-Weigh of Eugene, Oregon, WireLink is a multiplexing system. It uses two "black boxes"-one for the tractor and one for the trailer-that communicate with one another through the J560 connector.

WireLink uses frequency modulation, rather than spread-spectrum technology, to transmit messages between tractor and trailer. "Frequency modulation is used in fax machines, modems, radio, television audio signals, and cellular telephones," said Martin Ambros, chief executive officer of Air-Weigh. "It is mature technology that has been around for 75 years."

WireLink can be powered by the clearance lamp circuit or by the auxiliary circuit. The system can operate between 100 and 450 kHz, Ambros said, but it only needs 5 kHz when transmitting at 2400 baud. As such, it offers ample capacity for providing power to a wide range of electrically operated trailer accessories.

WireLink consists of one module and wiring harness for the tractor, along with a separate module and harness for the trailer. It also comes with mounting hardware, although the modules are small enough that they can be bolted or tied in place.

In its current configuration, the system uses one of the existing J560 wires to produce four switched circuits between the tractor and trailer. Like other multiplexing systems, WireLink employs a scheduler to control data flow. Each of the circuits has an assigned time slot during which data can be transmitted and received. During its assigned time slot, the circuit can transmit packets of data in a variety of formats. It is not locked into a specific protocol.

The latest version of the WireLink system has been in field testing since February 1. It is being marketed to trailer manufacturers by Hendrickson Vehicle Control Systems of Canton OH. Air-Weigh will service the aftermarket. Back to Basics

Grote Industries took a different approach. Rather than a system that provides power for current and future electrical needs, Grote emphasized the immediate need-to turn on an ABS malfunction lamp in the cab of the tractor.

Jim Hanson, vice-president of engineering, questioned the need for bidirectional communications between tractor and trailer, because the 2001 federal mandate simply requires that the trailer ABS illuminates a lamp in the cab should the trailer ABS malfunction.

The Grote Ultra-Plex system uses what Hanson described as low-cost interface circuitry to communicate multiplexed signals over the turn-signal circuit. The company's Power Interval Communication Technology (PICT) senses if the turn-signal line is dormant. If the line is dormant, it sends the signal.

Grote chose to power its system with the turn-signal circuit for several reasons. The advantages of using the circuit includes availability on all vehicles (including doubles and triples), the circuit is used infrequently, and it has low electrical noise.

Ultra-Plex is offered in three levels of sophistication. System I is the base level, providing a means of illuminating the in-cab ABS malfunction lamp. System II does the same thing and provides dome-light and auxiliary on/off switching. System III adds further capabilities, such as power for monitoring tire pressure, condition of perishable cargo, brake pressure, and other electronic devices compatible with J1587 and J1939 protocols.

"The more we talked to fleets about their options, the clearer the consensus became," Hanson said. "The primary function they were interested in was turning on the light to meet the 2001 mandate."

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