Hall-effect rotary-position sensors in transport and heavy industrial applications
Hall-effect rotary-position sensors are designed to measure the angle position of a moving element by utilising a magnetic field instead of mechanical brushes or dials. They use a magnetically biased, Hall-effect integrated circuit (IC) that senses rotary movement of the actuator shaft over a set operating range. Rotation of the actuator shaft changes a magnet’s position relative to the IC. The resulting flux density change is then converted to a linear output which can be used to provide feedback to either the operator or vehicle sub-system.
Solid-state Hall-effect technology provides non-contact operation. The internal section of the sensor uses a magnetic field, not a physical brush or wiper that is used in potentiometers. Wipers used in potentiometers can cause friction, which can reduce the product’s life. Using non-contact magnetic Hall-effect technology in a rotary-position sensor helps reduce worn-out mechanisms, lowers actuation torque and extends the product’s service life.
The Significant Seven: What Specifications Should Design Engineers Consider when Choosing Hall-effect Rotary Position Sensors?
- Is durability important? Engineers should consider the type of environment in which the device will be used. For harsh environments, engineers should specify a package that meets IP67 qualifications for enhanced durability. This is especially important for vehicles and machines that are being designed to typically operate in harsh climates and environments.
- How long is the device specified to operate? Check the product’s data sheet to determine the product’s documented cycle life. It may be better to have the sensor manufacturer perform this testing so that your engineering staff does not have to spend time doing this testing work.
- Should you specify an integral connector? Two important advantages of designing in a sensor with an integral connector are its smaller size and extended life. An integral connected sensor can be smaller than the overall package size of a sensor that relies upon a pigtail connection. This enables developers to design and build smaller overall system packages. Use of an integral connector increases durability because pigtails are notoriously fragile. Wires in a pigtail can become strained, frayed, eaten by rodents or crimped.
- Is EMI/EMC resistance important for your design? Radio waves of different frequencies can interrupt electronics. Automotive-grade EMI/EMC protection provides reliability in sensor performance against radio frequencies in the environment.
- Can you utilise a standardised I/O? Using industry-standard AMP termination, 32 mm mounting pitch and universal pin-out styles may help you save time and money. Standard I/Os can greatly simplify drop-in replacement because the mounting points, profile and pin-outs are similar to those of the incumbent device.
- How flexible do the sensors for your design need to be? Determine if you are working with one power setting or if the sensor should be able to work with a variety of input voltages. It could be beneficial to use position sensors that provide a wide span of operating voltages or ranges. A variety of operating ranges can provide design engineers the resolution needed in the span of travel in many common applications.
- Is your sensor manufacturer reliable? It is important to consider whether your supplier can provide the engineering, testing, quality and customisation expertise you need for your products. Additionally, it can be beneficial if the supplier knows and understands international standards, as well as manufacturing/shipping processes and policies.
Transportation Applications
Why is the Hall-effect rotary position sensor suitable for heavy duty vehicle equipment?
Foot Pedal Position Sensing
In heavy-duty vehicle equipment and other vehicles, Hall-effect rotary-position sensors may be used to replace the mechanical cable connection between the foot pedal and the engine. A mechanical cable can stretch or rust, potentially requiring regular maintenance and recalibration. Eliminating the mechanical cable can improve the engine control system response, benefitting the vehicle’s emission, improving reliability and reducing excess weight. This type of drive-by-wire system can be both safer and less expensive than cable-connected systems.
For example, a rotary-position sensor may be mounted adjacent to the pedal to measure how far down the pedal is pressed. The harder the operator presses, the deeper the pedal is depressed, allowing more fuel and air to be delivered to the engine so the vehicle moves faster. When the operator removes their foot from the pedal, the Hall-effect rotary-position sensor senses the change in position and sends a signal to the engine to reduce the flow of fuel and air across the throttle plate. The vehicle responds to this signal by slowing down.
Fig 1. Sensor may be used for foot pedal position sensing.
Honeywell’s RTY Series Hall-effect Rotary Position Sensors are designed to provide a minimum 35 million cycle product life due to its well-engineered bearing design and the related ICs.
Suspension/Kneeling Position Sensing in Buses and Trucks
Hall-effect rotary-position sensors can be used in buses and heavy-duty ride-height systems to sense travel of the suspension system. Buses utilise kneeling to lower their height so that passengers can board easily. The Hall-effect rotary-position sensor can be used on both ends of this application: one position sensor monitors the position of the control lever, and a second position sensor is deployed on a suspension arm or a linkage to monitor ride height.
Accurate position sensing validates that the vehicle is at the correct height for the application system’s requirement, improving vehicle ingress/egress. Large trailer trucks may also use Hall-effect rotary-position sensors to monitor trailer heights to improve warehouse docking efficiency.
Tilt/Trim Position Sensing for Speed Boats
Hall-effect rotary-position sensors can be used to monitor tilt/trim position for speedboats. The sensor accurately reports the angle position of the propeller, which can help the operator avoid damage and maintain optimum performance.
Agriculture and Irrigation Pivot Control
An interesting application for Hall-effect rotary-position sensors is irrigation sprinkler systems used by large farms. The sensor can monitor the angle range at which the sprinklers are irrigating. Is the irrigation system watering the section of the field intended, or is the system watering 360 degrees? This knowledge can help the farmer reduce water consumption and increase crop yield.
Industrial Applications and Valve Position Sensing
The control of process valves is vital in a wide range of industrial applications. Oil fields, nuclear power plants, food processing plants and beverage manufacturers require that valves accurately monitor positions. Hall-effect rotary-position sensors are used to monitor position in large and small valves to help ensure that the valve is closed or if it’s open, how open.
HVAC Damper Control
Heating, ventilation and air conditioning systems use rotary position sensors for damper control. On a cold day, an open damper may feed cold air into a room, causing the HVAC system to engage heat. An open damper may feed air into a room that has open windows, reducing the system’s efficiency and increasing heating and cooling costs. Effective use of Hall-effect rotary-position sensors, in conjunction with temperature sensors, allows the building manager to better control the HVAC system and reduce operating costs.
Designers want the best – Honeywell Hall-effect rotary-position sensors offer designers efficient and cost effective solutions in a wide range of transport and industrial sectors.
About the author:
James McKenna is Product Director, Honeywell Sensing and Control EMEA.
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