Application Data

ManualsBrandsSEC America ManualsSolar & Wind PowerTrailer Electrical Interface

P.O. Box 2266, S. Burlington, VT 05407

Tel: 802-865-8388 Fax: 802-865-8389

SEC America, LLC

www.secamerica.com

SEC

Power Converters for Interfacing Tractors and Trailers

The Objective

This paper describes three circuit configurations for achieving tractor trailer interfacing.

Prevailing methodologies are described together with an analysis of their reliability,

performance and relative cost.

The Purpose of Interfacing

Electrical Systems of North American Commercial vehicles are unlike those of Europe and the

NATO Military. They operate at different voltages and use dissimilar connectors. As a result

the direct coupling of a North American commercial trailer to a military highway tractor or

military trailer to North American tractor is not readily possible. The same holds true for cross

connecting European and American vehicles.

Electrical Trailer Interfaces make possible such cross coupling.

The Differences Between the Military and Commercial Electrical Pin Outs

See Figure #1 below for configuration differences.

Aux. Power

LH Blackout Marker/ Turn

RH Blackout Marker/ Turn

LH Service Signal

(Stop/Turn)

Ground

Brake

Sevice Clearance

(+marker)

Blackout Stoplights

Brake

Blackout Clearance

(+ marker)

LH Service Signal

(Stop/Turn)

Ground (White)

Tail & Licence (Brown)

Right Turn Signal

& Hazard (Green)

Stop Lamps &

ABS Power (Red)

Left Turn Signal

& Hazard (Yellow)

ABS (Blue)

Cont. Shared Power

Clearance, Side Marker &

Identification Lamps (Black)

24 Volt Connector Pin Functions For a Military Tractor

12 Volt Connector Pin Functions on Commercial Trailer

(Connector A)

(Connector B)

MS75021

SAE J560

Figure 1

Summary of content (7 pages)

PAGE 1
SEC SEC America, LLC P.O. Box 2266, Tel: 802-865-8388 S. Burlington, VT 05407 Fax: 802-865-8389 www.secamerica.com Power Converters for Interfacing Tractors and Trailers The Objective This paper describes three circuit configurations for achieving tractor trailer interfacing. Prevailing methodologies are described together with an analysis of their reliability, performance and relative cost.
PAGE 2
The Task of the Interface a) To ensure that the presence of signal at any given pin or combination of pins of the tractor are translated into an equivalent functional signal at the proper pin of connector of the trailer. b) To convert the voltage level of a power signal or combination of signals at the tractor output connector to a power signal of acceptable voltage at the intended pin of the trailer connector.
PAGE 3
The voltage is reduced by drawing current through fixed resistors. The value of any one resistor is determined by dividing the voltage which is to be dropped across the resistor by the current which it is intended to conduct. For this particular example, the voltage to be dropped across the resistor will be approximately 12 Volts, in order to bring the voltage to the Connector B pin down to 12 VDC from 24 VDC.
PAGE 4
) This characteristic of poor voltage regulation, i.e. a measure of how well the voltage is maintained at the output pin, would also limit the number and characteristics of accessories that could be loaded off the auxiliary (blue) pin. 5) If a short circuit were placed across the load at pin 5, the resistor R3 would have to withstand double the power dissipation that it would normally support under full load.
PAGE 5
Description of Figure 4 Bulk power is imported from the tractor through cables A and B to the 24V to 12V switching regulator mounted on the trailer. These cables must be of sufficient gauge in order to carry the complete electrical demand of the trailer. The Switching Regulator (SR) converts the 24 Volts to 12 VDC at a high efficiency. Signals are then applied from the tractor connector pins (connector A) to a relay network which is housed with the SR in the same converter box.
PAGE 6
Method C - Distributed Power Switching Regulators (Figure 5) High Frequency Switch 24v to 12v Switching Regulator Connector A Connector B High Frequency Switch 24v to 12v Switching Regulator A 1 J 6 K B L N M C H F 2 7 High Frequency Switch 5 3 4 D E 24v to 12v Switching Regulator 24 VDC High Frequency Switch 12 VDC 24v to 12v Switching Regulator Figure 5 Type C Power Converter Description of Figure 5: The Type C power Converter has multiple lower power switching regulators of the typ
PAGE 7
4) Because the entire trailer power consumption is channeled through multiple switching regulators, whatever little heat is generated, is dissipated evenly within the converter. Thus hot spotting is avoided. 5) Because each switching regulator is designated to deliver power for one function with limited current, the maximum current load can be electronically current limited in each regulator thereby eliminating the need for additional fusing.