India - Flag India

Please confirm your currency selection:

Indian Rupee
Incoterms:FCA (Shipping Point)
Duty, customs fees and taxes are collected at time of delivery.
Payment accepted in Credit cards only

US Dollars
Incoterms:FCA (Shipping Point)
Duty, customs fees and taxes are collected at time of delivery.
All payment options available

Bench Talk for Design Engineers

Bench Talk

rss

Bench Talk for Design Engineers | The Official Blog of Mouser Electronics


Attraction for Control: Magnetic Sensing in Building Automation Paul Golata

(Source: fanjianhua/Shutterstock.com)

You may have heard the expression “opposites attract.” This universally relatable phrase is derived from magnetism, where opposite poles, north (N) and south (S), are attracted to each other. You may remember this from playing with magnets as a kid. But, many people don’t realize that magnets are used in many systems and products in their everyday life.

Today’s buildings and homes are equipped with intelligent technologies for safer, more convenient, and energy-efficient living. Littelfuse is a global leader in magnetic sensing solutions. Its Building Automation solutions help designers create Internet of Things (IoT) devices that improve the safety, reliability, convenience, and energy efficiency of buildings. Sensor solutions provide information related to tampering, position, speed, and temperature, among other variables. The following will cover three magnetic sensor technologies: reed, Hall effect, and tunneling magnetoresistance (TMR) related to applications in building automation.

Magnetic Sensing Technologies

Three leading magnetic sensor approaches include reed sensors, Hall effect devices, and TMR sensors.

Reed

Reed sensors are reed switches packaged within an external housing for simplified mounting/connecting and additional protection against environmental influences (Figure 1). These sensors are typically mounted in mechanical systems. A bare reed switch can easily be mounted on circuit boards. However, for an application such as a door-security sensor, the reed switch needs a protective shell/housing for handling and mounting. These packages offer resistance to mechanical stress by protecting the bare glass of the reed switch. Reed sensors require zero power to operate. They can carry a load up to 100W and are available in NO, NC, CO in various sizes. The switches operate in X, Y, and Z sensing directions and are suitable for ultra-low-power battery applications. They can switch power level loads, incorporate the most mounting flexibility and exhibit stable operation over the widest range of temperatures.

Figure 1: Littelfuse reed switches operate in X, Y, & Z sensing directions and consume zero power to operate, making them suitable for ultra-low-power- battery applications. (Source: Mouser Electronics)

Hall effect

A Hall effect device is a semiconductor-based integrated circuit with Hall plates that respond to magnetic fields (Figure 2). Hall effect technology enables sophisticated sensors used in various automotive, electronic, and industrial product applications. Hall effect devices provide digital or analog output signals used for proximity and continuous rotary or linear positioning. Unlike a reed switch, a Hall effect device contains active solid-state circuitry, so it draws current at all times. These devices are available in digital, analog, and programmable configurations and are well-suited for high-shock or high-vibration environments. They are reliable to billions of operations and suitable for angular position sensing and high-speed switching.

Figure 2: The image shows an example of a hall effect device, the Littelfuse 55110 Flange Mount Hall Effect Sensor. Hall effect devices draw current at all times and are suitable for angular position sensing and high-speed switching. (Source: Mouser Electronics)

Tunneling Magnetoresistance (TMR)

Tunneling magnetoresistance (TMR) elements are a new type of magnetoresistance sensor. TMR sensors have better linearity, better temperature stability, higher sensitivity, and lower power consumption compared to Hall effect sensing technology available today (Figure 3). The sensors are solid-state devices with no moving parts. Like Hall effect, the sensors are available in digital and analog and require very little power to operate (lower even than that required of Hall effect sensors). Of the three magnetic sensors covered, they provide the highest level of sensitivity. They are eminently suitable for high-shock and high-vibration environments and offer reliability up to billions of operations. They also require the most miniature magnet needed to operate.

Figure 3: The Littelfuse TMR Switch series has better linearity, better temperature stability, higher sensitivity, and lower power consumption compared to Hall effect technology. (Source: Mouser Electronics)

Little Design Prudence

High-noise environments might require over-voltage (OV) protection. Both Hall effect and TMR sensors show sensitivity to electromagnetic interference (EMI) and electrostatic discharge (ESD). Proximity to motors, generators, reactive circuit components, or long cable harnesses (>1m) can cause damage. Design engineers are cautioned to consider the appropriate device protections, including options such as Littelfuse Transient Voltage Suppressor (TVS) Diodes for high-noise or Littelfuse SD05 Uni/Bidirectional TVS Diodes for low-noise situations.

Table 1: Magnetic Sensing Application Examples

Application Example Best Technology
Position: Battery Powered Door & window (open/close) Reed: Reed consumes zero current in the off state, ideal for ultra-low-power battery applications. Hall has significant current consumption.
Position: Non-battery powered Appliance door (open/close), lid detection Reed: Reed has the most mounting flexibility compared to Hall or TMR due to being omnipolar and able to sense in the x, y, and z-directions with one component. Reed is a two-wire device; while Hall and TMR are three-wires. If your sensor harness has long leads, there are high added costs to having an extra wire.
Flow rate: continuous Inlet in a tankless water heater Hall and TMR: Hall and TMR have faster switching capabilities in a smaller package with no wear-out mechanism.
Counting: rotation Gas or water meter Reed: Mounting flexibility and zero power consumption give reed an edge. TMR can be considered as well for its extra-long life and low-power consumption.
Counting: >500Hz Gear-tooth speed Hall and TMR: Hall and TMR can switch up to 15kHz, ideal for high-speed counting.
Level sensing: a single point Washing machine detergent level Reed: Reed has the most mounting flexibility compared to Hall or TMR. Reed is a two-wire device, while Hall and TMR are three-wires. If your sensor harness has long leads, there are high added costs to having an extra wire.
Relay Automated test equipment (ATE) Relay: Hall and TMR are not used in relay applications due to space issues of wrapping them in a coil.

Building Metering and Security Applications

Reed sensors have a clear advantage for anti-tamper applications. Reed sensors do not draw power and thus enable longer system battery life and provide 3D anti-tamper protection. In meter counting, reed is presently in the lead; however, TMR may make sense in some cases where battery life is not as important. Reed has a proven track record with 100M+ units in the field (and counting). Reed is the straightforward winner of indoor security applications. A changeover to reed sensors pays for itself in battery life and no service calls.

Conclusion

Today’s buildings and homes are equipped with intelligent technologies for safer, more convenient, and energy-efficient living. Littelfuse magnetic sensors are an attractive choice for control in building automation.



« Back


Paul Golata joined Mouser Electronics in 2011. As a Senior Technology Specialist, Paul contributes to Mouser’s success through driving strategic leadership, tactical execution, and the overall product-line and marketing directions for advanced technology related products. He provides design engineers with the latest information and trends in electrical engineering by delivering unique and valuable technical content that facilitates and enhances Mouser Electronics as the preferred distributor of choice.

Before joining Mouser Electronics, Paul served in various manufacturing, marketing, and sales related roles for Hughes Aircraft Company, Melles Griot, Piper Jaffray, Balzers Optics, JDSU, and Arrow Electronics. He holds a BSEET from the DeVry Institute of Technology (Chicago, IL); an MBA from Pepperdine University (Malibu, CA); an MDiv w/BL from Southwestern Baptist Theological Seminary (Fort Worth, TX); and a PhD from Southwestern Baptist Theological Seminary (Fort Worth, TX).


All Authors

Show More Show More
View Blogs by Date