by 
Keeping in line with the company’s strategy to deliver high-performance differentiated sensors and switches, Honeywell Sensing and Control rolls out its Nanopower Series of magnetic sensors, aimed as a replacement for reed switches in a variety of applications. These anisotropic magnetoresistive (AMR) sensor ICs deliver high sensitivity and extremely low power for battery-operated devices, as well as a solid-state design that provides an alternative solution to zero-power reed switches.
In an earlier discussion with Ashis Bhattacharya, vice president global strategic marketing & business development, at Honeywell Sensing and Control, he said switches and sensors are playing an increasingly important role in helping Honeywell’s customers to develop differentiated products, and one of the ways the company helps provide that differentiation is through the development of product platforms.
Ashis Bhattacharya, vice president, global strategic marketing and business development, Honeywell Sensing and Control
Honeywell continues to look at how it can roll-out platforms and differentiated products to help meets its customers’ requirements. “We continue along the path of high-performance differentiated sensors,” said Bhattacharya. “We want to continue pushing out our product platform strategy; being very thoughtful about the products that we develop, and working very closely with customers upfront because early involvement is key.”
“The focus remains on getting in front of the design engineers as early as possible so that we can work with them to select the best sensor option,” he added.
Part of the strategy also includes Honeywell’s distribution partners. “We want to make it easy for the distributor’s engineering and sales teams to sell our differentiated platform products,” said Bhattacharya. “The distribution model is based on two things – inventory on the shelf and having the product data and information available.”
For Honeywell this means developing product selectors or configurators to help distribution teams work with customers to select the right products quickly. Honeywell also monitors the configurations to determine which ones are high-volume parts. This enables Honeywell to guide the distributors in terms of which parts to keep in inventory.
“It is sometimes difficult for customers to select the best part for their applications, which is why the combination of Honeywell’s and the distributor’s engineering teams working together is the best way to reach out to our customers and make sure they make the right sensor choice,” explained Bhattacharya.
The Power of Small
Considered to be one of Honeywell’s most significant product launches this year, the Honeywell Nanopower Series is touted as the first AMR sensor to be offered in the nanopower range, compared to competitive products such as Hall-effect sensors that require as much as 3 microamps (uA) or higher.
The Nanopower Series is available in two magnetic sensitivities. The ultra-high sensitivity SM351LT offers a very low current draw of 360 nanoamps (nA) typical, and sensitivity of 7 Gauss typical operate and 11 Gauss maximum. The very high sensitivity SM353LT features a low current draw of 310 nA typical, and sensitivity of 14 Gauss typical operate and 20 Gauss maximum. The sensor ICs are housed in SOT-23 packages, measuring 2.9 x 2.8 x 1.45 mm.
At 310 nA, theoretically, a typical industry battery would run for more than 300 years if hooked up to just this sensor, said Bhattacharya.
“All of sudden it brings a magnetoresistive sensor into the realm where you can compare it to competitive products like reed switches, which normally would have been pretty tough to do,” said Bhattacharya.
“Coupled with the low power consumption is extremely high sensitivity,” Bhattacharya added. The high sensitivity allows the device to sense magnets at a greater distance so the air gap is much bigger between the sensor and the magnet.”
Lamar Ricks, director of technology and engineering, Honeywell Sensing and Control
Lamar Ricks, director of technology and engineering, Honeywell Sensing and Control, said this does a couple of things. With the increased sensitivity, designers can use smaller magnets, which lowers cost, and it gives them a lot of flexibility in terms of where they place the magnet while reducing concerns around mechanical tolerance and tolerance stack-ups within the assembly.
Honeywell also has priced the sensor at a cost that is comparable to reed switches and Hall-effect sensors, said Ricks.
A Low-Power Alternative
Design engineers are looking for an alternative to reed switches to reduce size and increase quality and durability, while maximizing battery life, said Josh Edberg, senior product marketing manager for Honeywell Sensing and Control.
This is the first product that can replace reed switches in many battery-operated applications thanks to its extremely low power, smaller package, stability over temperature, durable solid state technology (parts don’t wear out) and plastic molded packaging, said Bhattacharya. Reed switches are housed in glass tube packaging which lends itself to breakage.
With 360 nA of power, this is the first time an AMR sensor could really be considered as a replacement for reeds, primarily because reed switches consume zero power. As an example, the meter industry, which predominantly uses reed switches, told Honeywell it would consider an AMR sensor if it could get the power draw down to 500 nanoamps or less. In addition to the low power, these design engineers also needed high sensitivity (a large air gap), a temperature range of up to 85°C and high durability.
“Customers using reed switches didn’t have a viable alternative,” said Edberg. “Reed switches are a bi-metal mechanical-acting type of device, and the fact that these are electromechanical in nature, they wear out over time. They are made from glass and the packaging isn’t very robust so they tend to break, which results in quality and reliability issues.”
“But they are at zero power because of the way they are designed,” added Edberg. "The fact that we are down to the nanoamp range with the Nanopower series it gives these customers a viable alternative to a reed switch. The fact that it is a solid-state device delivers a good improvement in quality and reliability. We are giving new choices to companies trying to solve problems."
The Nanopower sensor ICs also can replace Hall-effect sensors. The Nanopower devices offer sensing distances of two times or higher compared to Hall-effect sensors, as well as senses in the parallel plane versus the perpendicular plane, which delivers greater design flexibility. It also reduces cost with the use of smaller magnets and offers lower power consumption than Hall-effect sensors that require 3 uA or higher. At 310 nA, the Nanopower sensors are one-fifth the power of a low Gauss Hall-effect sensor so it’s a pretty significant improvement, said Bhattacharya.
“Due to the significant price increases for rare earth magnets, design engineers using Hall-effect sensors have been looking for ways to decrease the total cost of design by using less magnetic material, or moving to a more common magnet in their applications,” said Edberg.
In addition to metering applications, the Nanopower sensor ICs can be used as a cartridge detection (position) switch in an infusion pump and door/lid detection in white goods. Although the initial “anchor” applications tend to be in the high-performance arenas, like metering, medical equipment and appliances, Honeywell expects this product to have much broader appeal including in consumer electronics applications such as hearing aids.
Several of Honeywell’s distributors are already stocking the Nanopower series including Digi-Key, Mouser, Sager, and TTI.
