Detailed Description
What Is a CANBUS / PROFIBUS Hybrid Cable?
A CANBUS / PROFIBUS hybrid cable is a multi-protocol fieldbus cable containing two independent shielded twisted pairs — one pair for CAN bus (120 Ω) and one pair for PROFIBUS (150 Ω) — within a single overall shield and jacket. It replaces two separate fieldbus cables in applications where machinery or test equipment uses both protocols simultaneously.
CAN bus and PROFIBUS coexist on many production machines for historical and technical reasons:
- CAN bus (and CANopen) dominates modern servo drive and motion control networking. Its multi-master arbitration, deterministic latency, and simple 2-wire physical layer make it the natural choice for real-time control of drives and I/O
- PROFIBUS DP is the most widely installed industrial fieldbus in the world — hundreds of millions of nodes in factories, process plants, and infrastructure. Many machines have legacy PROFIBUS I/O, sensors, and actuators that continue to operate reliably and are not replaced just because CANopen is available for the new drives
CAN vs PROFIBUS — Two Protocols, Two Pairs, One Cable
| Parameter | CAN Bus Pair | PROFIBUS Pair |
|---|---|---|
| Standard | ISO 11898-2 | EN 50170 / IEC 61158 |
| Characteristic Impedance | 120 Ω ±10 Ω | 150 Ω ±15 Ω |
| Physical Layer | Differential, 2-wire (CAN_H, CAN_L) | RS-485 differential, 2-wire (A, B) |
| Typical Data Rate | 125 kbps – 1 Mbps | 9.6 kbps – 12 Mbps |
| Colour Convention (Pair) | White/yellow + brown/green | Red + green |
| Termination | 120 Ω at each bus end | Active termination or 150 Ω resistor per segment |
| Topology | Linear bus with short stubs | Linear bus (RS-485); up to 32 nodes per segment |
| Primary Use in Machines | Servo drive control, I/O blocks, encoders (CANopen) | Remote I/O, sensors, actuators, HMIs (PROFIBUS DP) |
The two pairs are electrically independent — the CAN bus termination, biasing, and common-mode voltage have no effect on the PROFIBUS pair, and vice versa. The per-pair foil shield (100% coverage) ensures that the PROFIBUS RS-485 driver — which generates higher voltage swings and faster edge rates than CAN — does not couple noise onto the CAN pair.
Application Analysis
- CNC machine tools: The machine controller communicates with CANopen servo drives (X, Y, Z, spindle, tool changer axes) on the CAN pair and with PROFIBUS I/O blocks (coolant pump, chip conveyor, interlocks, tool magazine sensors) on the PROFIBUS pair — one hybrid cable in the drag chain carrying both fieldbuses
- Robot cells: A 6-axis robot uses CANopen for the servo axes (fast, deterministic motion control) and PROFIBUS for the end-effector I/O (gripper, weld controller, vision camera trigger) — the hybrid cable in the robot arm replaces two separate flex-rated fieldbus cables
- Mixed-fieldbus machine upgrade: A legacy machine with PROFIBUS networking is being upgraded with new CANopen servo drives. Rather than running a second PROFIBUS cable alongside the new CAN cable in the existing cable carrier, a single hybrid cable replaces both — saving carrier space and installation time
- Production line sections: A conveyor section with PROFIBUS motor starters and CANopen distributed I/O — the hybrid trunk cable runs the length of the section with drop cables at each field device
Why Choose Yichi for CANBUS / PROFIBUS Hybrid Cables
- Two independently impedance-matched pairs — verified by TDR: The CAN pair is 120 Ω and the PROFIBUS pair is 150 Ω. Yichi measures each pair's impedance with a time-domain reflectometer on every production length — two separate impedance certificates on one cable
- Per-pair foil shield for complete protocol isolation: The aluminium/polyester foil on each pair (100% coverage) ensures that the CAN and PROFIBUS signals do not couple to each other. The overall braid provides the external EMI barrier. This is a true individually-shielded-pair construction, not a single overall shield shared by both pairs
- PUR jacket for drag chain and machine duty: The hybrid cable often runs in the same drag chain as the servo motor power and feedback cables. The PUR jacket provides the oil, coolant, and abrasion resistance that PVC cannot match in this environment
- Red/green PROFIBUS pair and white/brown CAN pair — standard colour codes: Commissioning engineers can identify which pair is which at the connector without referencing the cable schedule. Standard colours reduce wiring errors
- One cable instead of two — reduced drag chain fill and installed cost: A 4-core hybrid cable occupies approximately 60% of the space and weight of two separate 2-core fieldbus cables, reducing the total cable carrier load and simplifying installation