Sensors Products Page 13 Sensors Products

2017 Littelfuse, Inc. Specifications are subject to change without notice Littelfuse.com 13 N S Magnet User Interface Ice Dispenser Reed Sensor Electronic Control Unit Frost Sensing Temp Sensing LED Light Appliances like refrigerators, freezers and wine coolers are used to keep food/ beverages cold and extend their useful life. These appliances contain lights to illuminate the inside compartments when the doors are open. However, the lights only need to turn on when a door is open. To accomplish this, a proximity sensor is needed to detect if the appliance door is open or closed. A reed sensor can be used to detect the position of the door. In refrigerators, a reed sensor is mounted to the frame of the appliance and a permanent magnet is mounted to each door. Each reed sensor and magnet pair is positioned so that the reed switch contacts close only when the door is completely closed. The position of the reed sensor's contacts can be monitored by an electronic control unit (ECU) within the refrigerator's electronics assembly to turn the interior lights on and off as needed. Reed sensors are ideal for a variety of position- and proximity-sensing applications where there is a need to detect the presence of a moving part in relation to a sensor in a fixed location. PROXIMITY SENSING USING REED SENSORS- Refrigerator Door Figure 1-Reed sensors detect the opening of refrigerator doors No physical contact required to operate the switch Zero power required for switch actuation Electrical contacts are within a hermetically sealed capsule that is immune to moisture, dust and dirt Wide operating temperature range adequate for use in cold temperatures Overmolded sensors provide additional protection against mechanical stresses and vibration Low-cost alternative to mechanical switch Features and Benefits: Suggested Products: Features and Benefits: Suggested Products: FLEX-14 (14 mm reed switch) MDCG-4 (15 mm reed switch) MDSR-10 (10 mm reed switch) 59025 (Firecracker reed sensor) 59040 (Firecracker reed sensor) 59140 (Flange mount reed sensor) Similar Applications: Refrigerators/freezers, dish washers, washing machines, rice cookers, coffee makers, vacuum cleaners and vending machines Hall effect sensors can be used to detect the movement of a garage door to stop the motor once the door has reached its open or closed position. Typically, a system of two Hall effect sensors, each associated with its own permanent magnet, is used to determine whether the door is completely open, completely closed or somewhere in between. One of the magnets is mounted on the chain drive of the garage door opener so that it is positioned directly next to the Hall effect sensor used to detect a closed door. The other magnet is positioned so that it moves with the chain and is located directly next to the other Hall effect sensor when the door is completely open. Similar to reed sensors, Hall effect sensors are ideal for position or proximity sensing where there is a need to detect the presence of a moving part in relation to one or more sensors in fixed locations. They offer extended life and reliability over reed sensors since there are no electrical contacts that are opened and closed. Common examples include door- and lid-position sensing in the similar applications listed. PROXIMITY SENSING USING HALL EFFECT SENSORS- Garage Door Receiver Power Supply Motor Drive Hall Effect Sensor Electronic Control Board S N S Figure 2-Garage door, Hall effect sensors mounted above garage door opener No physical contact required to operate the switch Wide operating temperature range adequate for use in hot and cold temperatures Hall effect sensor is an integrated circuit with no mechanical moving components Encapsulated sensors provide additional protection against environmental/mechanical stresses and vibration Reliable operation for millions of cycles Low-cost alternative to mechanical switches or infrared/optical sensors 55100 (Miniature flange mount Hall effect sensor) 55140 (Flange mount Hall effect sensor) 55310 (Flat pack digital Hall effect sensor) Similar Applications: Dishwashers, washing machines, vacuum cleaners, security locks on doors and vending machines APPLICATIONS

Previous Page
Next Page