Media Relations for a Connected World
Honeywell Sensing and Control article at ApplianceDesign Magazine
Design engineers have used reed switches in low-power, battery-operated applications for four key reasons. The mechanical reed switch offers “zero” power consumption, high sensitivity, and low cost. In addition, there has not been a suitable alternative technology. These advantages are not entirely true anymore thanks to new magnetoresistive (MR) sensing IC options that can provide position sensing with virtually no power consumption, high sensitivity, and high reliability and durability, while housed in a small package.
Before the development of solid-state sensors, magnetically-activated reed switches, which have been around for decades, provided a proven and inexpensive solution for position sensing. The reed switch consists of two ferromagnetic leads that are hermetically sealed in a glass capsule or tube. When a magnet comes in range of the switch, i.e., a magnetic field is applied to the leads, the contacts close creating a switching function.
Reed switches have remained a popular choice for many designers because of their simplicity as a mechanical switch and a lack of suitable alternatives, particularly in low-power applications. Reed switches have found homes in a wide range of products. Applications include consumer electronics, metering, security, white goods/appliances, medical equipment, robotics, and automation equipment.
Though reed switches are common among these types of applications, many designers also recognize that reed switches have some key disadvantages. These include quality issues due to breakage, both in the manufacturing process and in shock and vibration applications, limited life as a mechanical switch, size issues and reliability issues due to bounce effect (when the reed switch contacts bounce apart causing the application to turn on, off and then on again).