For many years I maintained the view that the SAE J1939 protocol, specifically its advanced network management capabilities, provides many great features to support any industrial application. SAE J1939 is an ingeniously designed protocol with very little protocol overhead, requiring only a minimal memory footprint that benefits the use of small embedded systems.
I am now in a situation where I can prove my point by working on two industrial applications that involve the SAE J1939 protocol. The first project involves controlling two Thomson Electrak linear actuators utilizing a small embedded system. That system consists of our
Arduino-Based ECU Development Board with Dual CAN Bus Interface plus the Arduino 4 Relays Shield. The task includes:
- Reading digital inputs (Forward, Reverse, Actuator Start, Error Reset)
- Reading a potentiometer analog input
- Reporting error condition per digital output (relay)
The potentiometer determines the speed of the actuator’s movement, which is converted into an SAE J1939 data frame. This requires the use of an SAE J1939 protocol stack, which we have developed for the Arduino Due.
The SAE J1939 data frame (PGN) controls:
- Position Command
- Current Limit
- Speed Command
- Motion Enable Signal
In turn, the actuator provides feedback per PGN, such as:
- Measured Position
- Measured Current
- Running Speed
- Voltage Error
- Temperature Error
I can’t go into more details of the application, but due to the SAE J1939 protocol’s small overhead, the requirements mentioned above are easily met by the Arduino Due system, making programming a breeze.
The above image demonstrates my hardware and programming setup. The Arduino system is embedded in a plastic enclosure. A DSB15 connector is used for IO control, while the two DSUB9 connectors provide the communication with the linear actuators.
If you need further information about programming SAE J1939 applications with the Arduino platform, please see:
I am in the process of writing a detailed application note, describing my experience with the Thomson Electrac Actuator, and providing more insights plus a working code sample for the Arduino Due. I will update this page as soon as it is ready for publication, so please come back frequently to check the current status.
Thomson Electrak Linear Actuator
The Thomson Electrak is an intelligent electromechanical linear actuator that eliminates the need for standalone controls.
As a result, it supports higher power and a broader application range than conventional hydraulic actuators.
In addition, it meets the most extreme OEM environmental acceptance tests, including IP69K.
The Electrak LL was designed with the railway market in mind. Railway equipment standards and safety regulations can be very demanding and require rigorous testing to ensure compliance. In fact, railroad equipment is exposed to some of the most demanding conditions. The Electrak LL actuator performs effectively despite harsh weather, heavy vibrations or high-pressure washing, making it ideal for opening and closing gravity bins or controlling a pantograph.
There are many industrial applications for which Electrak LL provides an ideal solution, but where it really excels are in applications in which mediumfrequency work is done on a daily basis. Examples include lifting, tilting, and grabbing operations in AGVs, logistic trains and lift trucks, or material handling machines operating a valve, hatch, or cutter back and forth during a production cycle. These types of operations often require multiple actuators sharing the load, which can be a challenge due to uneven loads and resulting binding effects. Electrak LL supports a more manageable task since its speed is load-independent and constant.
A Comprehensible Guide to J1939
SAE J1939 has become the accepted industry standard and the vehicle network technology of choice for off-highway machines in applications such as construction, material handling, and forestry machines. J1939 is a higher-layer protocol based on
Controller Area Network (CAN Bus).
It provides serial data communications between microprocessor systems (also called Electronic Control Units – ECU) in any kind of heavy duty vehicles. The messages exchanged between these units can be data such as vehicle road speed, torque control message from the transmission to the engine, oil temperature, and many more.
The information in this book is based on two documents of the SAE J1939 Standards Collection: J1939/21 – Data Link Layer J1939/81 – Network Management A Comprehensible Guide to J1939 is the first work on J1939 besides the SAE J1939 standards collection.
It provides profound information on the J1939 message format and network management combined with a high level of readability.