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Littlefuse Hamlin MDRRDT normally open close C form magnetic reed switch

- Jun 04, 2018 -


Contact Form Contact


Max. Contact Rating Maximum Power


Max. Switching Voltage Maximum Switching Voltage


Min. Breakdown Voltage Minimum Breakdown Voltage

200 VDC

Max. Switching Current Maximum Switching Current


Max. Carry Current Maximum Load Current


Max. Initial Contact Resistance Maximum Contact Resistance

100 mΩ

Min. Insulation Resistance Minimum Insulation Resistance


Max. Operate time Operation time


Bounce time


Max. Release time Release time


Min. Resonant Frequency Response Frequency

11000 HZ

Max. Operating Frequency Maximum Operating Frequency

30 HZ

Pull in Value

15-30 AT

Min. Drop out Value Minimum Reset Value

5 AT

Max. Contact Capacitance Maximum Contact Capacitance

1.0 pF

Test Coil Test Coil

Number of turns

Resistance resistance

4989 T

450 Ω


Reed switch principle:

Reed switch is the abbreviation of dry reed switch. It is a kind of contactless passive electronic switch element. It has the advantages of simple structure, small volume and easy control. Its housing is generally a sealed glass tube. There are two iron elastic reeds and an inert gas called a metal crucible. At ordinary times, two reeds made of special material in the glass tube are separated. When there is a magnetic substance near the glass tube, the two reeds in the tube are magnetized and attracted to each other under the action of the magnetic force lines of the magnetic field, and the reeds are sucked together so that the circuit connected to the node is connected. After the external magnetic force disappeared, the two reeds were separated due to their own elasticity and the lines were disconnected. Therefore, as a line switching device controlled by a magnetic field signal, the reed switch can be used as a sensor for counting, limiting, etc. (in the security system, it is mainly used for making door magnets and window magnets). It is widely used in various communication devices. In practice, the permanent magnets are usually used to control whether the two metal plates are connected or not, so they are also called "magnetrons".

Features and applications:

1, The dry reed pipe has a compact structure and a small weight, and can be installed in an extremely limited space, which is very suitable for a miniaturized device.

2. The switching elements of the dry reed switch are hermetically sealed in an inert gas atmosphere and will never come into contact with the external environment. The working life is long.

3, Dry reeds do not use sliding elements, so there will be no metal fatigue associated with all metal degradation, ensuring practically unlimited mechanical life.

4, The reed switch is very popular in mobile phones, program-controlled switches, copiers, washing machines, refrigerators, cameras, disinfection cupboards, door magnets, window magnets, electromagnetic relays, electronic scales, level gauges, gas meters, water meters, etc. Good application.


Reed switch usage notes:

1. Extreme care must be taken when cutting or bending the lead legs of a reed switch to avoid undue stress and damage to the glass-to-metal seal. Appropriate clamping tools must be used

2. The exposure to temperature and long exposure times may cause damage to the glass-to-metal seal (cracking, leaking, etc.), so fast and reliable welding techniques (processes) must be used. The recommended welding conditions are: 280-300°C for hand welding and 250-300°C for wave welding.

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