SWITCHES, DISPLAYS & UIs
Technology eases HMI design considerations in commercial vehicle applications
Robert Davies, marketing manager, EAO I
n a modern commercial vehicle, dashboards and binnacles provide the essential Human Machine Interface (HMI). Manufacturers of bare chassis usually only provide the HMIs essential to the driver, such as speed and fuel level indication, and controls and alerts to inform him/her about the status of airbags, seatbelts and other safety-related equipment. According to the purpose of the finished vehicle, manufacturers will need to fit additional application-specific HMI controls. Think of switches for light bars on emergency vehicles and controls for hoists, cranes, pumps, vehicle stabiliser jacks and cages. Some vehicles applications may call for more specialised functions such as camera displays, temperature sensors and hydraulic system monitors. Recent technological developments such as Controller Area Network (CAN) bus and Local Interconnect Network (LIN) bus are speeding and easing the process of retro fitting HMI controls.
The CAN (Controller Area Network) bus
Routine On/Off switches could be hard-wired through a relay directly into the cab or, increasingly, be connected via a CANbus. CANbus is a robust vehicle communications system that facilitates seamless communication between the vehicle’s various systems. The electrical architecture is simplified when communication is standardised throughout
the entire vehicle. CANbus operates in real-time, ensuring timely monitoring of the vehicle’s drivetrain and engine management system, together with other critical functions such as braking, engine control and transmission management. Because it is highly scalable, CANbus makes it easy to integrate auxiliary controls at any stage of the vehicle body-building process.
Most manufacturers of commercial vehicles are already producing electric and hybridised versions of their vehicles. Whilst there are still many devices and systems that can reliably function using traditional electro-mechanical switches and hydraulic levers, physical operator control in electrified vehicles is increasingly done using CANbus connectivity, a technology that is already doing sterling service monitoring conversion of DC to AC power for the electric motors and controlling the vehicle’s powertrain. A wider CANbus implementation via a Local Interconnect Network (LIN) bus node can replace hard-wired switches and CAN enabled electro-hydraulic controls further improve status monitoring, diagnostics and reliability.
Design Considerations Depending on the purpose of a final fitted-out vehicle, auxiliary controls may need to be fitted in the cab or outside the vehicle. Routine On/Off switches could be hard-wired through a relay directly into the
cab or increasingly be connected to a CANbus. Sealing levels of IP54 may be fine inside the cab, but external HMI controls will need to resist dirt, dust and liquid contamination and could call for front panel sealing to IP67 or IP69K level jet wash protection. Electrical connections may need an integrated Amp or Deutsch waterproof connector, or be fitted inside a waterproof enclosure.
The controls will need to be illuminated for nighttime use and carry unambiguous symbols to illustrate the switching function. Snap-in front mounting straight into the dashboard is fast and convenient for single controls, but when a larger number of functions are needed a keypad with multiple pushbuttons, fitted into a single cutout on the dash could be the better option. The DIN radio space is often pressed into service to accommodate application-specific controls with a slightly larger footprint. Commercial vehicle builders source the additional HMI switching components they need from specialised third-party suppliers. EAO is one such specialist, providing cost-effective automotive grade HMI components to car, bus, coach and specialist vehicle manufacturers throughout the world. The company’s Series 09 family includes 2- 6-, and 8-way keypads with RGB halo illumination. Indoor IP54 and outdoor IP69K keypads in the Series 09 can be hardwired or CANbus enabled using the J1939 CANopen or CAN Safety protocols. For easy configuration, the discrete switches and switch clusters in the Series 09 family can be provided with a NAMUR sensor, or optional LINbus connectivity. For exterior applications, EAO offers its Series 84 and Series 82 panel mount pushbutton switches featuring IP67 front and rear sealing. These devices feature integrated cables and connectors for easy connection into a vehicle dashboard.
46 OCTOBER 2024 | ELECTRONICS FOR ENGINEERS
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54
