Switches vs. Latches: Understanding the Key Differences and Their Applications

Ever wondered how magnetic sensors work? An important part of the answer lies in tiny components called switches and latches. Hall-effect switches and latches are fundamental non-contact sensor types that are essential for everything from smartphones and computers to sophisticated industrial equipment, automotive applications and most DC motors. This blog post will demystify the differences between these two magnetic sensor types and explore their diverse applications.

What is a Hall-Effect Switch?

Imagine a light switch – when you flip it “on,” the circuit completes, and the light turns on. A Hall-effect switch works similarly but on a much smaller scale using magnetics. It acts as a magnetically controlled gate, providing an output only when a magnet or magnetic field of sufficient strength is present.

For a switch, the on threshold, referred to as the magnetic operate point (B_OP), is the strength of the magnetic field required to turn the switch on. The magnetic release point (B_RP) is the magnetic field strength below which the switch turns off. Note that a switch can operate with a single magnetic field polarity (north or south).

Operation of a Hall-effect switch

Magnetic flux activates a Hall-effect switch

What is a Hall-Effect Latch?

A Hall-effect latch is a type of switch that is operated using both north and south magnetic field polarities. For a magnetic latch, once it is set to a particular state, it "remembers" that state even after the magnetic field is removed. To get a latch to change state an opposite (and generally equal) polarity magnetic field needs to be applied that exceeds the release point (B_RP). Think of it like a door latch – once you flip the latch, the door remains closed even if you let go.

Most DC motors will use one or more Hall-effect latches for their commutation, position or speed measurements.

Operation of a Hall-effect latch

Magnetic Switches vs. Latches: A Head-to-Head Comparison

The Importance of Low-Voltage, Low-Power Operation

In today's world, energy efficiency is paramount. As we increasingly rely on battery-powered devices, the demand for low-voltage and low-power components that minimize power consumption is higher than ever. This is especially critical in applications like mobile devices, wearable electronics, and the Internet of Things (IoT), where extending battery life is a constant challenge.

Low-voltage and low-power Hall-effect switches and latches are now commonly found in:

• White Goods: Making refrigerators, washing machines, and other appliances more efficient and intelligent.
• Smart Homes: Enabling seamless automation and control in smart locks, security systems, and energy management systems.
• Energy Meters: Improving accuracy and reliability in gas, water, and electricity meters.
• Medical Wearables: Powering the next generation of fitness trackers, health monitors, and medical implants.
• Robotics: Providing precise and reliable position sensing in collaborative robots, industrial automation, and more.

Applications for Switches and Latches: From Consumer Wearables to Smart Home

Switches and latches are everywhere in electronics. Here's a glimpse into their diverse applications:

• DC Motors (Latches): Electronic commutation, speed and position sensing for DC motors.
• Consumer Products (Switches): Bump sensors in vacuum robots and proximity detection for ear bud cases.
• Energy Meters (Switches): Magnetic tamper detection for electric utility meters.
• Power Tools (Latches): DC motor control, speed and position sensing
• White Good (Switches): Hall-effect switches can be used in washers, dryers, refrigerators for door, tray or shelf position detection and push buttons.
• Medical Wearables (Switches): Magnetic switches can be used to activate battery powered, wearable medical devices, preserving on-shelf battery life.

The Future of Hall-effect Switches and Latches

As technology advances, we can expect to see even smaller, more power-efficient and precise magnetic switch and latch sensors. New materials and manufacturing techniques will lead to improved performance and lower costs, enabling the development of ever more innovative and sophisticated electronic devices.

Allegro Microsystems’ Switch and Latch portfolio provides industry leading current consumption while allowing design flexibility at a lower overall solution cost.  For more details, take a look at our white paper; Maximize Your Battery Life With Micropower Switch and Latch Sensors.