In mobile hydraulics, valve control has moved from the lever to the solenoid and on to the CAN-based actuator. CANbus actuated valves cut wire count while improving control accuracy and diagnostics.
A solenoid valve needs separate wiring per section — up to sixteen conductors on a four-section valve. A CANbus actuated valve needs four conductors for supply and communication. The difference is not only in wiring: on solenoid valves control accuracy drifts as the coil heats up, whereas a CANbus actuated valve controls spool position with feedback and holds its accuracy.
Both are widely used, but their fields diverge. J1939 is the standard on vehicles and machines with a diesel engine; engine parameters and fault codes are read through a PGN structure common to all brands, typically at 250 or 500 kbit/s. CANopen is preferred in applications dense with sensors and valves — mobile cranes, platforms, concrete pumps — running at 125, 250 or 500 kbit/s. Which one is chosen follows the machine’s existing architecture and the devices to be connected.
Mistakes on the CAN bus produce faults that look like the valve’s doing. Both ends of the bus need 120 ohm termination, and after installation the bus should measure around 60 ohm. Cable must be twisted pair and shielded, with characteristic impedance between 108 and 138 ohm. Device negative supply must be taken directly from the battery rather than through the chassis; where a reference difference builds up over the chassis, devices run cleanly for a while and then stop transmitting. Line topology should be used wherever possible, with drop lines kept short.