Reed Switches

Reed switches, or magnetic reed switches, are versatile electromechanical electronic components designed to operate or actuate by applying a relatively low magnetic field. These switches comprise two or more ferromagnetic, nickel-iron alloy or other metallic, thin, and flexible reed contacts/blades enclosed in an inert-gas-filled sealed glass tube. These magnetically permeable contacts are hermetically sealed, kept apart by a small air gap, and activated by the presence/absence of a magnetic field. These specialised reed switches feature resistance against moisture, dust, and other environmental contaminants. Additionally, reed switches come in normally open or normally closed configurations and can be customised to custom sensitivity levels.

What are the Potential Benefits of Reed Switches?

Reed switches are simple yet versatile electronic components that offer several benefits in various applications. Here are some of the key advantages of using reed switches:

• They are compact and consume less power.
• Simple and sealed design.
• Function as simple on/off switches and other sensing elements, including proximity and level sensors.
• Suit hazardous environments and provide robust safety.
• Reed switches have a fast response time with magnetic sensitivity.
• They are highly durable with a long operational life.
• Provide protection against environmental factors such as dust, moisture, and gases. 
• Operate reliably over a broad range of temperatures.
• Offer non-contact switching and are cost-effective.

Operating Principle of Reed Switches

Upon applying a magnetic field near the reed switch, the integrated ferromagnetic material in the reed contacts becomes magnetised and attracts each other. This causes the switch’s closed state, a phenomenon when contacts come into contact and complete an electrical circuit. When the magnetic field is removed or reversed, the contacts spring back to their original position–breaking the circuit and returning to the open state.

Two Types of Reed Switches

Reed switches mainly come in two types based on their construction and operation:

• Form A/Normally Open – The Form A reed switch, also known as a normally open (NO) reed switch, is the most common switch type. In its normal state, the switch contacts are open where no current flows across the circuit. When a magnetic field is applied, the reeds are attracted and come into contact, closing the circuit and allowing current flow.
• Form B/Normally Closed – The Form B reed switch, also known as a normally closed (NC) reed switch, operates opposite the Form A switch. In its normal state, the contacts are closed, flowing current across the circuit. When a magnetic field is applied, the reeds are attracted and separated, opening the circuit and interrupting the current flow.
• Form C/Changeover Switches – There are also combination types combining the features of Form A and Form B switches, known as Form C switches or changeover switches. In their normal state, the contacts are closed (like Form B), but when a magnetic field is applied, they open (like Form A).

Typical Applications of Reed Switches

Reed switches find applications in a wide range of industries, such as:

• Door and Window Monitoring
• Robotics
• Consumer Electronics
• Medical Equipment
• Automotive
• Security Systems
• Proximity Sensing
• Liquid Level Detection
• Telecommunications
• Industrial Control Systems