Testing of magnets and reed switch performance
14 November, 2019 by
Testing of magnets and reed switch performance
Natalia Vavilina

Hello there!

We’ve done a test of the reed switch on our SimplePack Plus. You can find information about the reed switch we’re using here.

The purpose of this testing was to find out:

  • Best magnet type to use

  • Best magnet shape to use

  • Best magnetization direction

  • Best magnet strength to use

  • The best way to place the magnet

Best magnet type to use 

We have chosen the best permanent magnet type. Some use cases can be covered more efficiently with temporary magnets, but this implementation is rather advanced, so if you want to know more, write to us to

The magnet type to use is definitely Neodymium Iron Boron (NdFeB) as it is the strongest when it comes to power: size ratio. Even though NdFeB magnets are generally more fragile than other types of magnets, the accessibility (and lower cost) make them the ideal solution in case of mass deployments. The magnet type to choose is generally based upon your use case, but we went straight for the kill and chose NdFeB as the best type to use because most use cases that are covered by the reed switch or a combination of the reed switch and other sensors in SimpleHw devices include monitoring door/rolldown/covers opening and closing.

If you have a different use case, please read this and decide what’s best for you.

testing magnets performance with SimplePack

Best magnet shape to use

As above, in general, the best magnet shape depends on the use case. And please note that not only the shape matters but also the direction of the magnetization matters (which means that the two magnets of the same shape can have completely different induction lines and magnetic field form, more here: 

You have to choose the magnet shape according to the desired functionality, but generally, we have found that block magnets generally perform the best. You can look at the comparison of the magnets we tested down below in the table.

Best magnetization direction

There’s no best universal way to choose the magnet based on the direction of the magnetization, everything depends on the use case. In IoT, most use cases that use the reed switch with a magnet are monitoring various types of doors and other environments where you need to know whether something is opened/closed. Counting mechanical rotations of internal mechanisms of e.g. vending machines is also common. This means that a common feature of most use cases is the reed switch interacting with the magnet in a predefined way - they are both fixed and the position of where they are tells devices what data to report. This allows you to figure out the best way to place the magnet.

When we work with axially magnetized block magnets, it’s important to pay attention to magnet dimensions given by the manufacturer/reseller - please check this link so you know what we mean: - we are following up on this in point 5.

Best magnet strength to use 

This depends on whether you want the device to actually touch the magnet or for the device to come within close proximity to it. We recommend the second option which requires a stronger magnet but has less room for error. Feel free to check out the table below where you can find what magnet shape & strength activated the reed switch counter at what distance.

The data in the table in the magnet strength column is the pull strength of the magnet (the highest possible holding power measured in kilograms). It‘s the force required to pull the magnet away from a flat steel surface where the magnet and the surface have full surface-to-surface contact. The results are the distance from the reed switch that activated it.

CylinderHeight 20mm, diameter 10mm5 kg8 mm
Height 40mm, diameter 10mm*
5 kg19 mm
Height 40mm, diameter 10mm
10 kg28 mm
DiscHeight 2mm, diameter 25mm
3,2 kg3 mm
Height 10mm, diameter 25mm
8 kg8 mm
40 x 10 x 57,5 kg20 mm
40 x 10 x 7
9,2 kg25 mm
40 x 10 x 10
15 kg31 mm
Block40 x 20 x 10
20 kg45 mm

*this cylinder magnet was magnetized in a different direction than the one below it

Best way to place the magnet

This is a case by case matter. With the information above, you should have a better understanding of how to implement the device in order to properly fit your use case. You should consider what you want the device to report and based on that, find the best way to attach it where needed. Also, the direction of magnetization is an important thing to consider, as outlined in point 3!

We need to mention axially magnetized block magnets again as the way you place them plays a crucial role in the performance of the solution. The best way to do so is to make sure that the height of the magnets exceeds other dimensions (because you can have the exact same shape of a magnet - let’s say 20x10x05 and 10x05x20 and the performance will be drastically different). The magnet should be parallel to the reed switch with one of the poles facing up - this ensures a magnetic field of such shape that the switch of the reed sensor is opened or closed smoothly.

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