Views: 156 Author: China Micro Switch Manufacturer Publish Time: 2020-08-08 Origin: https://www.unionwells.com/
What are reed switches?
Reed switches are simply electrical switches that are controlled by a magnetic field. The first reed switch was brought into existence by Walter B at BTL around 1936. In its very basic form, a reed switch is a composition of two ferromagnetic non-static metal contacts inside a glass envelope. Usually, the contacts remain open, and are closed when a magnetic field is sensed. Or they could be normally closed anytime there is an application of a magnetic field. The actuation of the switch can be made possible by electromagnetic coil. Another way to do it is by bringing a permanent magnet close to the switch. The moment you get rid of the magnetic field, both contacts in the reed switch are restored to their original position.
The metallic part inside the reed switch is what is known as the reed. Its flexibility can be traced to its wide and thin nature. It looks every inch as a typical reed plant. That term reed is also appropriate as an external wire lead or the internal part. A very practical application of this device can be seen in door opening systems, particularly when it is employed as proximity switches for security alarms.
Other types of reed switch
There are also other types of reed switches. Those ones are made of a flexible reed which motions between a normally-open contact which is fixed and another normally-closed contact which is fixed as well. Unlike the common types, this type of reed switch has a non-ferromagnetic normally-closed contacts, which is closed as a result of the actions of the dynamic reed’s spring force. While reed switches with more than one pole do exist, there are reed switches with just one pole that can do the same thing for applications that are meant for multiple poles.
A complete electrical circuit is created when a permanent magnet or an electromagnet creates a magnetic field close to the reeds large enough to move it into motion. The reeds have sufficient spring force inside of them that will repel them away from each other when they are no longer under the influence of the magnetic field. A reed switch contact is usually made of materials like tungsten, iridium, ruthenium, or rhodium. Some other reed switch versions are made with contacts that are mercury wetted. The challenge with such switches is that they ought to be installed in specific position, so that they do not melt on the bridge and create an unnecessary connection between the reeds.
You would want to expect the switch contacts to react with the atmosphere, which might result to things like rust and corrosion. Well, that is not the case of the reed switch because its contacts are properly protected from any atmospheric influence, thanks to its sealed glass material. That way, it is ultimately safe from anything like corrosion or rusting. Since it has been hermetically sealed, reed switch happens to be the safest bet for areas where the atmospheric conditions are extreme. You cannot use most other types of switches in those situations because they would almost constitute a serious hazards to the users.
Important quality of the reed switch
One fantastic quality that helps the reed switch to stand out from other switches is the fact that it has a high level of sensitivity. This feature can be easily determined by the strength of the magnetic field available to influence the operations of the reeds. It is measured in ampere turns (AT). This is equivalent to the amount of current present on the coil multiplied by the number of turns on the coil. If the AT is low, then the sensitivity of the reed will be high. It is an inverse kind of relationship. In other words, reed switches that are smaller in size tend to end up with higher sensitivity because of the parameters used in defining it.
A reed switch can be explicitly used to vary different loads. From smallest voltages to be big voltages, from the smallest currents to bigger magnitude currents, and also for all forms of frequencies, the reed switch can be heavily relied upon to control the unit efficiently. Many other switches that are also magnetically controlled, unfortunately, do not have this advantage, because they are limited in what they can vary. And most of them are not used to directly control items like motor, solenoid, or lamp.
Reed switches do accommodate little current leakages unlike most solid state devices. This is another advantage of this switch type. For instance, in the medical industry, they are highly appreciated because they are better suited for patients who are to be protected from excessive current leakages. Thanks to its hermetically sealed glass envelope, this switch type can almost be used in any environment. They are the best for fire-prone environment as well as places where switch contacts are likely to be corroded due to environmental factors.
How to wiring a reed switch
Dissimilar to some other electrical switch, the reed switch seem to be quite easy to connect. You just have to connect the positive part of the power supply to one of the terminals of the switch while the negative power source goes to the other terminal. Of course, the earth from the power source should be placed on the remaining terminal of the reed switch. At this point you are ready to use the reed switch.
Whenever a solid state device is unfit for its purpose, a reed switch is the next reliable option that comes to mind. They are most suitable anytime power consumption as well as electrical interface appears to be a challenge. Reed contacts on the reed switch do experience surface wear and tear because of the frequent opening and closing of the contacts. That is why the manufacturers have decided to rate its longevity on how many operations it is used for, and not the usual years or number of hours