Vibration Motor Comparison Guide
One of our most common enquiries is from people all over the world who want to implement vibrations in their application but have never done so before.
The following guide will outline the main types of vibration motor, the various options available for each, and highlight the differences in a comparison table.
Important Vibration Motor Acronyms And Terms
There are a number of technical terms and acronyms that some readers may find daunting, so here we outline some of the more important ones. This list is by no means comprehensive.
- ERM = Eccentric Rotating Mass, this is the weight found on rotating vibration motors that produce the vibration
- BLDC = Brush-less Direct Current, this motor does not have brushes hence it is brush-less
- LRA = Linear Resonant Actuator, a unique type of vibration motor similar in concept to a speaker. Note the form factor is the same as the coin motors below – but they are not ERMs
- Coin Motor = ‘coin’ describes the form factor, they are flat and round. They are actually just ERM motors, there are also brushless versions available
- SMD / SMT = Surface Mount Device / Surface Mount Technology
- PCB = Printed Circuit Board
- Vibration Amplitude = this specification describes the vibration intensity that a motor produces, and is always listed as a normalised value so that different motors can be easily compared.
MTTF = Mean Time To Failure
Get in touch
Speak to a member of our team.
Looking for our products?
Reliable, cost-effective miniature mechanisms and motors that meet your application demands.
How To Select A Vibration Motor
Regardless of your particular application, you will usually be able to identify some key requirements such as vibration speed, driving voltage or the maximum permissible motor size. Once these requirements are identified it will be much easier to select the most appropriate motor from the large (and growing) range of vibration motors that we offer. Our Product Catalogue shows all of our stocked motors, while our Sales Engineers have access to a large database from which we can recommend motors.
Note that almost all factors are dependant upon the voltage applied. The voltage controls the speed of the motor, the faster the motor turns the higher the vibration amplitude and frequency. See the sections below for more information, the figures in the table are all at the Rated Voltage.
Vibration Motor Form Factor
This exposed style of vibration motor is perhaps the most common as it is uncomplicated and cost-effective, the ERM is clearly visible and unprotected.
Compact and easy to use, they are typically supplied with an adhesive backing. This style of motor can also be considered enclosed, as the ERM is protected by the body housing. Note that although LRAs are in the ‘coin’ form factor, they are very different internally – see the coin motor here and the LRA here.
The motor itself is fully covered by plastic or metal housing, designed to be over-moulded. They are our motors that are most resistant to the ingression of dust and liquid. We have other articles covering over-moulding and IP ratings.
These motors are covered by plastic or metal housing, but have ventilation or mounting holes in the casing. They have no moving external components and are useful when the ERM should be protected from objects or users but don’t require the resistance of encapsulated motors.
Highly popular and low cost, ERM style vibration motors are available in a wealth of sizes. From a diminutive 3.2mm up to 45mm diameter, they can be used in all manner of applications.
LRAs are a relatively new style of vibration motor, and the available range of sizes is slowly expanding. They are typically coin form factor, 8 ~10mm diameter and 2 ~4 mm thick.
BLDC vibration motors are available in similar sizes as the brushed ERMs, although the range isn’t quite as expansive.
Longevity refers to how long the motor can operate before failing. It is common to express this as the Mean Time to Failure, which is measured in hours. There’s some statistical wizardry behind these numbers, you can read about it in AB-019: Lifetime of DC Vibration Motors (MTTF & FIT).
While brushed DC motors are cost-effective and easy to operate, they are not as robust as their brushless counterparts. The most common failure mode is due to damaged or worn brushes, although on rare occasions the bearings may fail first.
As they do not have brushes BLDC and LRA vibration motors are more reliable, with lifespans in the thousands of hours. LRAs are particularly reliable as they have no rotating parts.
Vibration amplitude is dependant upon the voltage applied. Essentially, a greater voltage increases the torque output, which increases the speed, which increases the force. Almost all specifications and characteristics on the datasheets are given at the rated voltage of the motor. Typical Performance Characteristic Graphs show how these vary with the voltage.
There are other characteristics that impact the vibration amplitude, but these are set during manufacturing. We have a wide range of ERM vibration motors available at a variety of different vibration amplitudes in stock, but we are also able to customise models for specific applications.
For LRAs, a similar theory applies. The greater the voltage applied, the greater the acceleration of the internal mass, the greater the output force. However, as the LRA comprises of a single unit, they are not as easily customised.
Vibration frequency is also dependant on the voltage applied, as it is directly related to the speed of the motor. It may be necessary to select a motor with a specific vibration frequency because it can be important for specific applications and affects the level of displacement, however many find it a non-critical factor in their application.
LRAs are much more restrictive on frequency. They are driven by an AC signal which should be extremely close to their rated resonant frequency (±5 Hz) because of their high ‘Q factor’.
Vibration Motor Mounting Techniques
Just as there are many different form factors there are many ways to mount vibration motors. This section is more concerned with the shape of the vibration motor rather than how it operates, i.e. the external design instead of the internal design.
Coin type motors and LRAs typically feature an adhesive backing, while others may have mounting holes on the front face. They can be inserted into enclosures or strapped to bulkheads. A growing number of applications are implementing haptics effects in wearable or flexible technology.
Vibration motors are commonly mounted onto PCBs, there are a number of ways to ensure they have good electrical and mechanical contacts. Each of the bullet points is a link to more information on the type of connector, there’s also a full Application Bulletin linked below.
A rubber boot helps ensure a reliable fit in injection moulded enclosures, one side of the motor features two sprung terminals which interface with contacts on the PCB.
SMD / SMT
Designed for convenient and efficient use in production volumes, this style of motor is well suited to pick-and-place assembly and typically comes supplied in reels. They are then soldered using a process known as ‘reflow soldering’.
Small holes in the PCB match the position of mounting pins on the motor. They are then soldered in place, some pins transmit power to the motor while others fix the motor to secure it in place. Some motors have pins for mounting, but still, use leads for power connections.
Typically seen on coin type vibration motors or LRAs, this is a convenient method for quick mounting using the pre-attached adhesive backing. Simply remove the tape and stick in place.
This method allows for the effective transmission of vibration as the motor is typically mounted directly against the enclosure. The enclosures can be injection moulded or machined making them very space efficient but note the tolerances to ensure ERMs aren’t impeded.
‘Bulkhead’ means a large flat surface, like the side of a chute or hopper.
There are many ways to attach a vibration motor to a bulkhead, whether that be by using P Clips, mounting holes on the motor face, or specially designed mounting brackets like the 445-000 (part has since been depreciated, along with 345-XXX vibration motors). Typically used for larger vibration motors it allows them to be attached to a variety of objects in many different orientations.
In Flexible Materials
An increasing amount of applications require vibration motors to be mounted in flexible products that are often worn on the body. The eccentric mass needs to be free to rotate, so coin type (including LRAs), enclosed, encapsulated motors are all ideal for such applications because they are less likely to be impeded or damaged.
This is the voltage at which the motor is designed to be powered at. Typically the motor can be driven below or (slightly) above this voltage, however, its performance will change as explained in the provided the Typical Performance Characteristics Graph. It is common to deliberately adjust the voltage to achieve a variety of different vibration patterns and effects.
For reliable operation, the minimum recommended driving voltage is the Maximum Start Voltage (formally called ‘Certified Start Voltage’). If you intend to vary the voltage, there are 4 important values to consider.
The direction of vibration really sets apart the ERMs from the LRAs. As ERMs rotate a mass, there is force produced in two axes – both perpendicular to the motor shaft. This applies to coin motor ERMs too, their shaft is extremely short and is in the centre of the circular surface. As coin motors are mounted on their back, they provide a good alternative vibration direction to cylindrical ERMs. As the vibration direction comes from the mechanical movement of the motor, it is the same for brushed ERMs and BLDC ERMs.
LRAs are different. They operate with a mass on a spring that moves along one axis, therefore they only produce vibration in one axis. This is typically in the ‘Y’ or vertical axis for a coin-type LRA mounted on its back. However, there are horizontal LRAs also available – the important point is the single direction of vibration.
The concept of vibration direction is best understood when visualised. Our previous Application Bulletin on user interfaces discusses this topic in detail, including accompanying diagrams like the one above – check the link below for more information.
AB-014: Mechanical Layout of Vibration Motors for Typical User Interfaces and Controls
Cost Vs Longevity
Commercial reality dictates that most applications require a product that is suitably priced, which partially explains the popularity of cost-effective brushed vibration motors.
ERMs are inexpensive, easy to implement (reducing time spent designing and testing), and require few additional electronics. The tradeoff is that their commutator and precious metal brushes will eventually fail. However, some models have been tested to get thousands of hours of operation – which in many applications exceeds the life expectancy of the product.
LRAs are high performance and reliable alternatives for haptic feedback. However, they require a driver to operate which can see a slight increase in the complexity and total cost.
The high build quality of a BLDC motor carries a higher price, however for some applications, the total lifetime cost can be comparable to an equivalent brushed motor.
While the large number of differences and options may make selecting a motor style difficult, the reality is that once the design has been suitably constrained the most appropriate motor will often be clear. We have trained engineers on hand to help you select a motor, don’t hesitate to get in touch.
Sign up to receive new blogs, case studies and resources – directly to your inbox.
Resources and guides
Discover our product application notes, design guides, news and case studies.
Explore our collection of case studies, examples of our products in a range of applications.