Reed switches in Floor detection in Elevators and Lifts
Most people are aware of Elevators, or lifts, as they are called in certain areas of the world. The electrical motors in elevators however well programmed to start and stop at the required floors, need feedback on the exact position of the elevator box to apply the final brakes. This is to ensure that there is less than inch level difference between the elevator floor and the actual level floor. This feedback is very accurately provided by latching reed sensors that stay in an actuated state as an elevator passes floors on the way up and stay in a non-actuated state as the elevator passes floors on its way down. These Latching reed sensors are mounted on every floor and are changed state by the magnet on the elevator, as it moves up or down, past each sensor. The polarities of the magnet and the Reed Sensors can be matched differently, and the actuated states of the sensor can either be latched for floors above the elevator and non-latched for floors below the elevator, or vice versa. The latched and unlatched condition of the sensors can be compared to electronic flip flops with built in driver circuits, and have the added advantage of switching higher loads.
The construction and design of reed switches and selection of magnets for latching applications requires years of experience. We work very closely with our elevator OEMs to provide custom, cost-effective solutions and work backwards to provide the best contact coating specifications for reed switches, that make it very easy for users to build latching reed switches for such application using custom magnets.
Applications are classified as Position Sensing, Pulse Counting, Electromagnetic or Relay, Temperature Sensing or Magnet Biasing types. This application is classified as follows and the link gives more information on best practices to help select the most suitable AT band and matching magnet.
The Reed Switches and Sensors used in such applications need to be robust, durable and efficient in meeting a high life expectancy. Our engineers work hard in life testing our products under various conditions, and our intention is to ensure end product durability and life. Although we wouldn’t want to restrict any of our products for use in only certain applications, the recommended products for use in this application are listed below.
R2E Latching / Bi-stable SMD Reed Sensors
|Polarity Sensitive, "remembers" last actuated state, 19.5 mm SMD and low-profile SMD pitch, capable...Continue reading|
MS-228, M8 Threaded Cylindrical Sensor
|Omin polar, 0.75 mm pitch M8 thread. Rugged body and high wall thickness of...Continue reading|
MS-328 Flat Pack Reed Sensors with Actuator
|Screw mountable, 8.0 mm slot widths, matching actuator magnet, capable of switching up to...Continue reading|