Reed Switch and Reed Sensor Applications

Introduction

We strongly recommend reading the previous sections on Reed Switch basics, key parameters and operational characteristics in order to establish requirements for your personal applications.

Because the Reed Switch is completely hermetic, it can be applied to more switching applications than any other switching device. It can be used as a complete sensing component by itself, and can easily be fitted into special sensing requirements without any complicated process or high tooling costs.

There are so many existing and potential applications for Reed Sensors that it would be impossible to discuss them all here. Some of the basic applications are covered, however, which will provide some guidelines for your application. If you need any further information, please contact our applications department where our fully-qualified engineers will answer questions pertaining to your application requirements. Free samples are also available.

Using the Reed Switch alone may seem the simplest approach, but be aware that this requires proper consideration and precaution. Reading our Precautions section is indispensable. It is important to note that the Reed Switch is a glass capsule and therefore fragile. Keeping this in mind while mounting the switch in a stress-free environment will guarantee success. Failures or erratic operation may be discussed with our engineers. If necessary, we can recuperate the application and manufacture an entirely fault-free sensor. It may be less expensive to have us design and manufacture the entire sensor from the outset. Whatever your decision, we will be happy to collaborate with you.

Reed Switch Selection

Initially, the most important step is to select the correct RS for a given application. Any RS can perform simple switching of either a transistor or digital gate. The question is one of size and cost. Consult our RS selection chart to make the best choice. When switching a load, 'hot' switching a voltage at a particular current level, it is important to select the RS with the correct wattage corresponding to the required voltage and current level. Where sensors are required to have a long life span (10âßßs of millions of operations), particular attention must be paid to the load to be switched. When switching 5 Volts @ 10 mA or less, life span is not a problem. Consult our life span section or contact our engineers if necessary.

Reed Sensor Packaging

The utmost care is required when packaging a Reed Sensor. Carefully protecting the glass to metal seal from potential damage or stress will result in a fault free application. During packaging, the Reed Switch may suffer stress through bending, cutting, soldering, welding, potting, or encapsulating. The damage is not always visible, but erratic behaviour may result. Packaging the Reed Switch without inducing any stress is critical to proper operation and long life, whether it is packaged by the user or by the Reed Switch Sensor manufacturer. Collaboration between the user and the manufacturer must be strictly coordinated.

Consult our Reed Switch Sensor selector guide to discover the packaging styles and sizes available. Many special packages with specific connectors or connections exist, but are too numerous to show in our Data Book, so do not hesitate to inform us of your special packaging requirement.

When determining the closure and opening distance, care must be taken to include the distance within the package as part of the sensing distance. Standard packages offered by MEDER electronic will take this distance into consideration in the design. However, on special packages, keep this distance in mind because it does affect sensitivity.

Plastic packages are easiest to tool and are the least expensive. However, if a rugged enclosure is required, use of a non-ferromagnetic material may be the best approach. Do not include any nickel, iron, or cobalt in the package. They will shunt the magnetic field.

Lead lengths and connectors can be adapted to all potential requirements.

Reed Sensor Mounting

Multiple options are available when mounting a Reed Sensor. However, the sensor must not be mounted on or near any ferromagnetic material. This is because magnetic flux lines travel better in ferromagnetic material, thus causing a shunting effect on the magnetic field. However, in our operational section, we have shown that in some cases, this effect can be used positively, but the presence of magnetic materials in the vicinity of the application must be taken into account. Magnetic components must also be considered: inductors, transformers, toroids, for example, as they will influence the magnetic sensing circuit.

Reed Sensors can be supplied with a variety of mounting possibilities: simple slots for screw hole mounting; double-back adhesive tape; they can be screwed simply into panels; they can be PCB mountable with pins; they can have surface mount 'J' or 'gull' leads for mounting on SMT boards. Other variations exist so that all application mounting possibilities may be met.

Reed Switch Electrical Connections

All Reed Sensors may be electrically connected in a variety of ways. The most common are PCB mount, leads of varying length for soldering, leads with connectors and surface mount soldering. Some lead wires will have an array of terminals available as options for making the electrical connection. Most of our series offer terminals on the leads for quick solderless connections. Surface mount soldering is becoming increasingly popular. Our MK1, MK15, MK16, and MK17 were all designed with that in mind.

Reed Switch Sensing Applications

Reed Switches can be used in an infinite number of sensing applications. Here are some of the more common applications which may enable you to find a solution to your particular requirements.

It is important to remember that no external power is required in a Reed Sensor application. The Reed Switch in most cases, once closed will switch the load you require.