An electrical switch operated by an applied magnetic field; the Reed Switches are effective sensing solutions. It is a magnetically operated switch that is normally opens when there is no magnetic field present within its defined sensing or “activation” range. When a magnetic field is present in proper alignment and of sufficient strength, the contacts of the reed switch will close and complete the circuit. If the magnetic field is removed, out of proper alignment, or weakened in strength, the contacts of the reed switch will open again, disconnecting the circuit. In a circuit, it is used to control the flow of electricity. A reed switch is used to activate or deactivate a circuit at a time of our choosing. Using simple magnet interaction to open and close its contacts, they consume no power in their normally open state. To enable using the reed switches used in almost any environment, they are hermetically sealed.
Reed switches have normally open (NO type) or closed (NC type) ferromagnetic contacts;
Reed switches are available in bare glass or over molded packages with a variety of mechanical, electrical and magnetic characteristics. Activated using magnetic fields, the reed switch is activated using external magnetic field. Digital signals can be supported with just 2 leads.
Features of reed switch:
• Reed switches are hermetically sealed within a glass tube with inert gas and do not receive any influence from the external atmospheric environment.
• Quick response because of small mass of moving parts.
• The structure comprises the operating parts and electrical circuits arranged coaxially. Reed switches are suited to applications in radio frequency operation.
• Reed switches are compact and light weight.
• Superior corrosion resistance and wear resistance of the contacts assures stable switching operation and long life.
• With a permanent magnet installed, reed switches economically and easily become proximity switches.
Why use Reed Switches?
• Requires negligible power to operate it
• Requires only two wires whereas most solid-state devices require three wires
• Contacts are hermetically sealed
• Can be used to directly switch a variety of loads ranging from nanovolts to kilovolts, femtoamperes to amperes, and DC to radio frequency
• Most economic non-touch switching solution
• Not ESD sensitive
• Various sensitivity ranges available
• Voltage drop across reed switches is much lower than semiconductors