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Reed Switch

This page covers reed switch basics and mention reed switch manufacturers.

As we know relays operate comparatively slower. Hence for fast switching they are not useful. For such fast switching applications such as in telephone exchange reed switches are used. The reeds are thin strips of easily magnetizable and de-magnetizable material. They are usually manufactured such that reeds are sealed in a glass tube containing inert gas such as nitrogen. This help reduce corrosion of the contacts.

reed switch

Let us see working of reed switch as depicted in the figure with normally open contacts. The switch is operated either by bringing a magnet near or by passin a current through the coil surrounding it. By doing so, reeds get magnetized and attracts each other and complete the electric circuit. They get separated when the magnet is removed or the current flow stops through the coil.

The circuit shown is used to protect transistor controlled relays and reed switches. As shown, when the current in the coil of a reed switch falls to zero, a large voltage gets induced in the coil due to its inductance. This voltage could damage any transistor used to control the current in the coil as shown. If a diode is connected in reverse bias for the supply voltage, it offers easy path to induced voltage. This stops building it to a very high voltage.

Reed Switch manufacturers

Following are reputed reed switch manufacturers.
1. MEDER electronic
2. Hamlin electronics
3. Reed Relays and Electronics
4. Standex Electronics
5. Standex Electronics
6. Mouser electronics
7. STG Germany
8. HSI Sensing
9.Comus international
10 Jameco Electronics
11.Littelfuse
12.Cherry electrical products

Littlefuse has recently released high precision extension to its reed switch product lineup. The part numbers are MACD-14 and MASM-14(surface mount version) series. They have following silent features:
• Switching capability of 200V DC at upto 10W power.
• Sensitivity range: 10-30 AT
• hermetically sealed to withstand in harsh environment
• through-hole and surface mountable

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