WELCOME TO OUR FREQUENTLY ASKED MOTOR CONTROL QUESTIONS
A common issue, especially with sensorless brushless DC motors
‘Cogging’ is a general term (possibly even a colloquial term) used to describe a brushless motor appearing jumpy or jittery. It is much more prevalent at lower speeds than higher as high speeds tend to smooth out the motor considerably. An example of ‘cogging’ can be seen in the video below in the unoptimised brushless motor and controller example.
Note how the motor stutters and jumps at the startup phase – rather like an engine on a cold day without enough choke on.
What are the options for eliminating cogging?
There are several potential solutions for reducing or eliminating cogging which are all worth exploring. Some are more relevant to certain applications than others but it is going them.
- Switching to a brushless motor with more poles – the more poles a motor has the smoother it will perform at lower speeds (where most cogging occurs).
- Use a sinusoidal brushless motor controller – sinusoidal controllers perform better at lower speeds and hence are likely to reduce cogging.
- Check current settings. One common cause of cogging is that the startup current settings are not set appropriately. This is especially true in applications where startup occurs under load.
- Use a carefully optimised brushless motor controller. We regularly optimise our brushless motor controllers for a range of customers to help address the challenges of specific applications. As can be seen in the video above, this can lead to a significant benefits.
How do I know which solution is best for my application?
There are certain solutions which may be completely impractical for your application – whether it be a cost or technical issue. For example, higher pole count motors or sinusoidal controllers typically (though not always) increase the cost of a project.
Solutions such as optimising a trapezoidal brushless DC controller like the ZDBL15 are very low cost and (depending on the required volume we can even carry this out at no cost). This method is highly reliable because it tailors the controller not just to the motor you have but also to the specific demands of the application.
If in doubt – give us a call – we’re happy to help
As mentioned above, finding the right answer to resolving a cogging issue is often application specific. We would therefore encourage you to get in touch with us if you are having this issue. You can click here for contact details for us and if you have any questions please ask.
Power density is the amount of power that a given motor can handle per unit volume. In really simple terms we might call it the power to size ratio of a particular motor.
The reason this particular measure is important is also relatively straightforward – namely that, in applications where size (and also weight) are important factors, the power density of a motor is a critical performance measurement. This is because it indicates the relationship between the size of a motor and the power that motor can deliver. In lightweight (often battery powered) applications such as drones or automotive applications, high power density can be hugely important.
OK – so the higher the power density, the better for my application?
Not necessarily no.
There are other factors to be considered when thinking about the right motor for your application. For example, the relationship between speed and torque that you require, do you need reliable positioning or intelligent control in this way?
A typical (though not always the case) feature of many motors with high power density is higher speeds and less torque. This may well mean that you then require additional gearing to get the speed and torque combination required for your project. Adding gearing adds inefficiencies and weight and therefore goes against the power density of the whole package.
Likewise stepper motors offer very poor power density but for certain applications are the only type of motor which can really achieve what needs to be done.
I need the best possible power density I can – what motors should I use?
Almost certainly you will want brushless DC motors. However, the exact type and design of brushless motor you require will depend on the specific application you have. To find out more about the different types of brushless motor and the pros and cons of using each type please click here.
Depending on your application you should also think carefully about whether you opt for sensored or sensorless brushless DC motors as this could also have an impact on the performance options you are able to achieve. There are a large range of potential brushless DC motor controllers available to drive all types of brushless motor but you will need to think about this when designing your product.
Final thoughts: an important consideration but don’t lose sight of other factors at the same time
For certain applications – largely space and weight sensitive applications – power density is undoubtedly a very important factor. However, for other applications it may be less of an issue and other factors may trump the issue of power density as a factor.
Strip the right length of wire
One of the most common problems when wiring in a motor controller is that the user inadvertently strips either too short or too long a length of wire.
Too short and it can become hard to get a good connection in a screw connector (and especially hard if a soldered connection is required). Too long and you run the risk of the cables shorting either on each other, on the driver itself or on something else in the application. Depending on the motor controller that you are using, a short like this could completely blow the controller.
Typically, 5-10mm is a good length but this will vary depending on the type of connector that you are using.
Consult the datasheet or startup guide first!
One of the most important aspects of wiring up components such as motor controllers is wiring things up in the correct order.
Typically this involves connecting all the various outputs to the controller before one connects the power connectors but it is always best to consult the datasheet or user guide first.
A good workman doesn’t blame his tools because he chose to buy good ones and bring the right ones.
Whilst you would never catch any of us blaming our tools, we would also hope that the same goes for you.
Buying good quality tools can make a huge difference in the quality of job you are able to achieve, especially where soldering is required. Getting a nice, clean length of wire is critically important in getting a good, solid connection into the controller. Trying to strip wires with a blunt penknife might not get you where you wish to be.
Hold your nerve!
With fiddly wiring jobs it can be common to get exasperated and try and force the issue.
If you find yourself about to jam a frayed wire into a stripped screw connector or picking up gaffer tape at any point then it’s generally better to put the kettle on and have a think.
Take care to follow the wiring diagram and use different coloured wire where possible
It is always a good idea to use different coloured wires where possible. These will enable you to clearly distinguish wires when connecting them and can help prevent connecting the motor phase wires the wrong way round.
If this is not possible try and use pen or electrical tape to mark the cables individually so you know exactly which ones you’re dealing with.
Can I drive a sensored brushless DC (BLDC) motor with a sensorless brushless DC motor controller?
Sensorless brushless motor controllers can work very well with a sensored BLDC motor
The quick answer is yes, you can, provided that you connect everything up correctly. That said, it is important to be clear about your reasons for doing this.
A sensored brushless motor is a brushless motor with sensors in it. A sensorless brushless motor is exactly the same as a sensored brushless DC motor with the exception that it does not have sensors installed. Many manufacturers make exactly the same motor (in terms of frame size and electrical specifications) but simply offer it in sensored or sensorless variants.
This therefore means that a sensored brushless motor can in essence be treated exactly like a sensorless brushless motor. To do this you must first ensure that the phase connections are wired in correctly but the hall sensors wires are ignored. It is important to remember that, if you do this, the motor that you are using will then become a sensorless motor so any performance characteristics that you were getting if you had been using a sensored brushless motor controller will now be different.
Performance characteristics may vary depending on the brushless motor controller
Any technical information you may have on the motor which is based on it being run as a sensored motor will also no longer be entirely accurate – this is especially true at lower speeds. If you are not entirely sure about this or have any questions please give us a call to discuss.
It is worth remembering that there is no obvious reasons to do this in practice with the exception that sourcing motors for specific applications is sometimes difficult and we have had clients in the past who have only been able to find a sensored brushless motor which met the torque/speed requirements their project required. Again, if you have any specific questions here please feel free to give us a call or email.
Customisation is always an option
Depending on the volumes that you are purchasing for your project it is also usually possible to talk directly to the manufacturer in order to get the sensors removed and a discount applied.
It is likely that you will need to setup the sensorless brushless motor controller to deliver the correct drive pattern depending on the specification of the sensored brushless DC motor that you have. It is always important to take into account the number of poles and key electrical characteristics of the motor.
If you have any questions about the best way to setup your brushless motor and controller then please contact us. Our team can even set the controller up for you specifically for the motor that you have.
A range of technical support to get your motor control project moving
We offer a variety of technical support for both our stock range of motor controllers and any customised or bespoke motor controllers that you may purchase.
Our business model is fundamentally built on delivering custom motor controllers which fit the applications you need perfectly and meticulous technical support is a major part of this.
One thing that we won’t ask you to do (at this point anyway!) is to ‘submit a request’ or ‘request a ticket’. Instead if you buy anything off us you’ll be able to contact us direct via email, phone or our online chat service to request additional help or support. If you’ve made the decision to invest in a design project with us then we’ll provide you regular updates on progress and will organise site visits at the appropriate stages of the design process.
We understand that investing in and operating motor controllers can be a big decision for you and that many of the features and possibilities may seem somewhat daunting or confusing. That’s why we do our best to deliver comprehensive technical support. Our company motto – ‘Motor Control Simplified’ encapsulates this philosophy – we want to make the process of using our motor controllers so simple and straightforward for you that you will wish you used them years ago.
Our core aim is to remove all of the stress that can be involved with motor controllers to enable product designers, engineers and other professions to get on with the job that they want. We think our technical support options fit in with that vision.
Motor control support over the phone
Our UK based engineers are available on the phone to talk through any problems that you may have. If you have a project where you are looking for the right solution they are happy to discuss this with you. Alternatively, if you have already purchased a controller from Zikodrive we can assist with setup, performance issues or anything else.
Simply call +44 (0) 333 123 7130 and choose the relevant option for your enquiry. We will then either deal with your issue straight away or make arrangements for a call back if all our technical team are busy at that moment.
Our passion is motor controllers, don’t hesitate to get in touch and we will be happy to help.
SKYPE OR TEAMVIEWER SUPPORT TO MAKE QUICK MODIFICATIONS TO motor controller parameters or settings
If you have purchased a new board and need help setting this up or want to make quick programming changes we can assist with this in a number of ways. One increasingly common option is to arrange a Skype or Teamviewer meeting with our technical team in order to enable them to see your motor setup in action. We can then advise on the best route forward or make real time programme changes (provided you have the equipment setup to do this).
Depending on the controllers that you have we can assist you with making significant firmware changes to them. We have several customers who purchase large volumes of the same hardware but who then install a range of programmes on these controllers in order to customise them for their specific customers. If they have a new customer with new requirements they simply give us a call and we will book a session in to get things up and running
ON SITE SUPPORT TO HELP GET YOUR MOTOR CONTROL PROJECT MOVING?
We offer fully insured on site technical support from qualified engineers. We will usually incorporate this into any bespoke design projects that we will do – unless otherwise requested. However, if you are considering purchasing one of our standard range of motor controllers and would like a site visit to assist with setup of these controllers then please contact us and request a visit.
What costs are involved in modifying an existing ‘off the shelf’ stepper motor controller or BLDC Motor Driver?
every motor control project is unique
Perhaps not surprisingly, the costs of modifying an existing stock stepper motor controller or BLDC Motor Driver to turn it into a customised motor controller depend largely on the extent of the modifications that you require.
As a basic guide we would split this cost up into the tooling costs involved in making changes to the board and then the design and testing time required to ensure the motor controller meets the exact specifications you require. A simple modification which requires only a change of connector or something similar will require very little design time. However, the addition of extra features or a reworking of the motor controller into a smaller design will potentially take quite a lot of time and therefore add cost. We will however put together a fully costed proposal before we start so you are clear and what you are getting into.
tooling costs to get your motor control project off the ground running
Any modifications that are made will require custom made tooling to be made in order to then deliver them as full production units. Typically the cost of this is £1000. Depending on the customised motor controller you are looking for we may be able to achieve what you are looking for with a plugin board which could save you money on this (See below for more information on this). However, any physical changes which are required will inevitably attract these types of costs.
development time to get your motor control project from concept to success
The development time required to deliver your modifications obviously depends on two main factors. The first of these is the complexity of what you require and how different it is to the standard version of the stepper motor controller or Brushless ESC. To provide a basic idea our charges for this are £40/hr for design and testing time and £80/hr for any on site work that may be required. If it is as simple as adding one or two onboard features to an existing stepper motor controller or BLDC Motor Driver then this may only require 1-
The second major factor is how many projects we are already committed to. As a small firm we have limited technical resources available and if all our team are tied up with projects then we may not be able to start the project immediately. If this is the case we will be very clear about this from the start and will be able to provide you with a date when we can start work. Whilst we understand that this can be frustrating if you are keen to get your project moving as fast as possible, it is always better to be clear at the start rather than making promises we cannot keep.
Please note that we are always more than happy to provide fixed price quotes for changes if preferred.
Please also note that the development times associated with customisations and modifications tend to be much shorter than bespoke design.
Whatever you are looking for or contemplating for your project we would strongly encourage you to get in touch with us via phone, online chat or email to start a conversation about how we may be able to help. Please note approximately 50% of our work is based on bespoke and custom design and as we almost always retain the IP of these designs we may have something in our library that is very close to what you require and can be quickly modified.
what about optional break-out or plugin boards for your motor control project?
For some applications it may be more cost effective to use an existing stepper motor controller or brushless ESC and purchase a custom made plugin board to deliver the features you require. This is generally the case where modifications are much more about physical user interfaces such as additional buttons, pots or displays and is often also true where additional communications types or similar are required. If you are anticipating relatively high volume (200+ a year) then it will probably be lower cost to get a custom made board. For anything below this, adding a plugin board could save you money.
get a motor controller that delivers
If this is something that you are considering then the first port of call is to talk to one of our engineers about your requirements. They will advise on the most cost effective method for achieving your project requirements and we can then take the project from there. If there are several potential ways of carrying out the project we can provide quotes and clear advice for the range of options that you have.
the short answer is yes, however …
Yes, purchasing full intellectual property for a motor control design is an option but not one which is commonly pursued (or indeed encouraged).
The core business model through which we deliver value for money and attempt to spread technically advanced controllers at competitive prices is built on the accumulation of intellectual property and design knowledge then enabling us to deliver lower cost, customised motor control solutions. It is therefore clear that if we sold the design rights for every motor controller we had ever developed we would not be able to do this.
That said, we do understand that with certain projects, particularly those which are moving towards patents and copyright protection, that this is a key requirement. In cases such as this we will be happy to explore your requirements and advise. Sometimes this may include licensing, sometimes it can include a restricted intellectual property transfer agreement in which you purchase the design rights to the controller that you require with key documentation covering the limitations of this.
Formal Legal Agreements
Any Intellectual Property transfer will be subject to a formal intellectual property transfer agreement drawn up by our solicitors which will outline the exact terms of the agreement and which will be included as part of the overall quote.
Case by case basis
By definition, the requirements of each specific project are different and we therefore prefer to deal with IP ownership requests on a case by case basis.
To discuss this in detail we would suggest that you CONTACT US as this type of issue is best dealt with on a case by case basis.
You can also read more information about our bespoke motor controller design projects, or some case studies of motor control design work we have previously carried out.
How complex can the programming of the standard range of Zikodrive Stepper Motor Controllers or Brushless Motor Drivers be?
why should I use a motor controller from zikodrive?
One of the main advantages of using a Zikodrive programmable motor controller is that our motor controllers are fully programmable. We are continuing to work on our standard customer software Zikosoft but until this is released we can customise all of the settings you require or help you use third party systems to programme our controllers.
QUICK SETUP OF THE BASIC PARAMETERS OF YOUR STEPPER MOTOR CONTROLLER OR BLDC MOTOR DRIVER
At its most basic, we can set up a stepper motor controller with basic settings such as current and speed. This is particularly useful for those customers who require a motor driver that runs in a set speed range or who just need a motor driver which will accurately and repeatedly run at a set speed. Our aim here is to simplify things as much as possible for our customers by setting up the basic parameters on the stepper motor controller or brushless motor driver before you even use them.
STEPPER MOTOR DRIVERS AND BRUSHLESS ESCS THAT MAKE IT SIMPLE AND EASY FOR YOU
The central aim of this type of programming is to deliver motor drivers which are set up and ready to go for the specific application that you need. Many of our customers have previously used stepper motor drivers or brushless ESCs where they have to try and manually set up specific speeds using either a pot or other mechanical methods (including breaking resistors off the PCB!) but with Zikodrive Motor Controllers we can preset exact parameters into your motor controller so that you can simply take it out the box and plug it in….
Once you have confirmed that you are happy with everything we will then assign a part number to enable you to re-order the exact pre-programmed controller that you need whenever you need it.
This is an option which has been taken by a number of UK and European companies who we now regularly supply with standardised Zikodrive hardware with bespoke firmware for their specific applications. It is a proven path for getting customised motor controller performance at a stock controller price.
MORE COMPLEX PROGRAMMING OF YOUR STEPPER MOTOR CONTROLLER OR BLDC MOTOR DRIVER…
As useful as the simple parameter setting programming can be in a range of applications it is just the tip of the iceberg of what can be achieved with Zikodrive Stepper Motor Controllers or Brushless ESCs.
For more technically advanced and demanding motor control applications we can set up motor controllers to run specific sequences. These sequences can then be triggered with a signal input or can be setup to be modified using external switches or pots. Always bear in mind that we can set up any motor controller to operate with a range of external user controlled inputs such as buttons, pots and more.
If you want to get a sense of the level of complexity that can be achieved then a good place to start is with the iD Stepper Motor Controller specifically developed for Boxer Pumps . This features a significant amount of complex programming in order to incorporate automatic pump calibration, dosing monitoring, a full user interface and second tier calibration interface and a whole host of other features.
CONCLUSION – COMPLETE PROGRAMMING OF STEPPER MOTOR CONTROLLERS AND BRUSHLESS MOTOR DRIVERS TO MEET YOUR PROJECT’S NEEDS
Just ask! If you have a specific requirement that you would prefer to be directly programmed into a controller rather than operated by UART or similar protocol then we are probably able to help. Products such as the ZD4 Stepper Motor Controller are designed to be customised and so we will need to work with you to develop your specific application.
How does closed loop control of brushless motors work, what brushless motor controllers do I need and what are the advantages?
What does closed loop brushless control involve?
Closed loop brushless control involves driving a motor but then monitoring the speed of the motor and using the monitored information to inform the behaviour of the driver. This then creates a closed loop in which the motor and controller are working in a closed loop in which the output of the controller is monitored and adjusted according to the behaviour of the motor. This is particularly useful in applications in which there is a need to maintain an exact speed all the time or is also a useful method for monitoring for potential faults such as jams.
There are (broadly speaking) two methods by which brushless motors can be operated in a closed loop.
The first is using a sensored brushless motor and using the onboard hall effect sensors to monitor the rotor speed and position. This can then be fed back into a brushless motor controller which can then process the information and change the way in which it drives the motor according to the core requirements of the application.
The second method involves using sensorless brushless motor controllers but then using the back electro-
is one method better?
Broadly speaking, most engineers would argue that using hall effect sensors is ultimately the most accurate and therefore the best route to go down if you need a closed loop brushless system. This largely because the onboard sensors can tell you exactly where the rotor is and what speed it is doing and essentially do the job of an encoder but without the additional cost of buying an encoder.
That said, sensored motors and controllers do typically cost more money which can be a downside depending on other applications.
They also are ultimately less reliable than sensorless brushless motors because there are more things that can go wrong, typically the sensors. This is an especially important factor to consider in applications where there may be lots of dust or other issues which could interfere with the sensors.
If one of these sensors breaks then the controller will not be able to operate and this could lead to an expensive repair. To learn more about the differences between sensored and sensorless brushless motors and controllers and their applications click here.
Which brushless motor controller do I need for each method?
To use the sensors on a sensored brushless motor you will need to use a sensored brushless motor controller. A sensorless brushless motor controller will be able to drive a sensored brushless motor but not by using the sensors.
For a closed loop brushless system based on back-
This sensorless brushless motor controller will be able to drive either a sensored or a sensorless brushless motor controller in a closed loop system by using the back-
The type of brushless closed loop system we would recommend will ultimately depend on the nature of the project or application that you have. Both systems have pros and cons which are technical and financial and ultimately need to be considered in the context of your specific project.
The different types and terms used to describe brushless motor controllers (including ESCs, controllers, drivers and more)
what do they all mean?!
Fundamentally all of the various types of brushless ESC or brushless motor controller that we discuss below all do basically the same job, making a brushless motor operate in the way that you would like it to. Some of these are much simpler than others and all have certain pros and cons both technically speaking and commercially speaking. Many of these terms are used interchangeably so you need to be careful but the terms are generally used with a specific focus.
So, let’s get started then….
THE DIFFERENT TERMS USED FOR BRUSHLESS MOTOR CONTROLLERS
Brushless ESC –
Brushless Motor Controller –
Where a brushless ESC will typically convert an incoming voltage into the right drive pattern for a brushless motor, a brushless motor controller can be much better optimised to deliver a range of performance advantages, including closed loop control using back EMF to deliver constant speed under a variable load. It is important to note that a brushless motor controller may be designed specifically for a sensored brushless DC motor (as opposed to a sensorless brushless motor). Always remember that a sensorless brushless motor controller can drive a sensored or sensorless brushless motor but a sensored brushless motor controller can only drive a sensored brushless motor.
Sensorless Brushless Motor Controller –
BLDC Motor Driver –
Can I use a sensorless brushless motor controller to start a sensorless brushless motor under load?
Starting a sensorless brushless motor under load with a sensorless motor controller – the short answer…
Yes, although successfully (and reliably) accomplishing a sensorless brushless hard start is one of the hardest aspects of operation of sensorless brushless motors and does need some tailoring to your specific motor choice and application.
THE KEY PROBLEM WITH STARTING A SENSORLESS BRUSHLESS MOTOR UNDER LOAD – HOW TO APPLY STARTUP POWER WITHOUT KNOWING THE ROTOR POSITION…
The key to successfully using a sensorless brushless motor controller to drive sensorless brushless motors in an energy efficient and practical way is the timing of the power input into the motor coils. If the timing is slightly out then this will cause major inefficiencies within the motor and can even act as a brake on the motor’s turning (depending on the rotor position).
This can also create excess heat and wasted energy (a common issue with lower cost brushless ESCs which often start to overheat and burn out relatively quickly).
When a motor is up and running it is relatively easy to know the rotor positions on a sensorless brushless DC motor as this can be detected using back EMF and then optimised at the testing and setup stage through testing and understanding the exact motor being used.
However, at the startup stage it is impossible for the BLDC motor driver to know the inertia on the rotor or the rotor position on a sensorless BLDC motor because there is no movement from which to gain the back EMF information which the brushless motor controller can use to pinpoint the rotor location.
It is therefore quite common for sensorless motors to jump around a little at the start if they have not been properly optimised because the brushless motor controller being used is powering on coils on an assumed position with the aim of pulling the rotor into that pattern when it will then function normally.
Hence, the often stuttered startup followed by a sudden boost as the rotor aligns with the drive pattern (this is often compared to an engine struggling to start, coughing and spluttering, before suddenly roaring into life).
Optimised sensorless brushless motor controllers start first time under load
OPTIMISING SENSORLESS BRUSHLESS MOTOR CONTROLLERS TO START UNDER LOAD
The key to optimising a brushless motor controller to start under load is firstly to know the motor that you are working with and its application and then to optimise the brushless motor controller to the key specifications of this particular motor and the application. Key variables such as inertia, number of poles, inductance and more can all be used to optimise the controller to run well.
The Zikodrive brushless motor Vert Rotor case study provides a good example of this.
Once this is done the running of the motor will be as efficient as possible and this knowledge can then be used to inform the startup sequence for the motor. Knowing the number of poles and the motor inductance is a big part of this as this can be optimised specifically for the motor.
However, advanced programming in the ZDBL range of sensorless brushless motor controllers is also carefully optimised to read changes in back-
A TAILORED SOLUTION DELIVERS THE BEST RESULTS
There is no doubt that starting a sensorless brushless DC motor under load is not the easiest aspect of motor control to master but with the ZDBL series of sensorless brushless ESCs we have developed a system which works well in a huge number of applications.
Sometimes this can require a significant amount of optimisation and hard work but in the long run it pays off, particularly where such performance is a key part of your application.
For more information you can browse the Vert Rotor Brushless Motor Controller Case Study or browse our range of brushless motor controllers (brushless ESCs) for more information.
If you have any questions at all please do not hesitate to contact us to discuss with one of our engineers.
you can use Sensorless brushless motor controllers for dosing – but it can be tricky.
Using sensorless brushless motors and their respective controllers in dosing applications is a particularly difficult application but one which can be carried out successfully with a little care and attention.
CAN’T I JUST USE A FLOW METER FOR BRUSHLESS DOSING?
There’s a number of ways you can set up for successful brushless dosing of which flow meters are certainly one. Don’t forget however that using a flow meter can be expensive and complex. This is particularly true when one considers that there are other alternatives which are worth investigating first….
THE SIMPLEST BRUSHLESS DOSING SOLUTION – DOSING BY TIME…
The quickest and simplest way of setting up a sensorless brushless ESC or sensorless brushless motor controller for dosing applications is to use time. In essence this can be done through an automated system which will calibrate a specific liquid through a specific tube diameter over time. Once the amount dosed/time is known it is then possible to calibrate the system using a simple control mechanism so that if a certain volume is required, the controller will know that it needs to run for a certain amount of time. For example, if the calibration process has worked out that 10s will deliver 100ml of a particular substance then a user could input 75ml into the controller and it would run for 7.5 seconds.
WHAT ARE THE PROBLEMS WITH USING TIME AS THE KEY VALUE IN DOSING APPLICATIONS?
The key issue with using time as the key ‘measurable’ in a dosing application is that time is not volume – in other words we are not accurately measuring the volume of a particular substance but are approximating volume by time. To use an example, if one considers a large barrel of a particular chemical – for example chlorine – which is being dosed into a swimming pool at regular intervals to ensure the water remains fit for human use then the output of this barrel must be at the bottom of the barrel.
As the barrel reduces the pressure on the fluid will reduce. Whereas the first few doses will have been under additional pressure (as a result of gravitational pressure), the last few doses require careful pumping to be delivered. If time were used as the key variable by which the volume was determined, it is therefore quite likely that there may be a significant difference between the first dose out of the barrel (which would have been heavily gravity assisted) and the final dose (which would potentially have had gravity opposing it).
The result is a changing volume as the pressure changes.
NOTE: it is worth highlighting here that in applications where the input pressure on a pump is stable, time can be a very good measure provided all other factors remain constant (such as tube diameter, distance pumped etc.). However, in practice most applications have changing pressure of some sort so time will never be quite as accurate as other methods
USING BACK-EMF TO MEASURE THE NUMBER OF TURNS OF THE BRUSHLESS DC MOTOR
The ZDBL Series of Sensorless Brushless Motor Controllers use back-EMF most commonly as a means of determining (and potentially adjusting) the speed of the motor. However the ZDBL BLDC Motor Controllers can also be set up to count the rotations of the motor which can therefore give a much more accurate indication of volume (depending on the type of pump being used) because if we know the volume of the pump and the rate it pumps at then we can determine that a set volume requires a set number of turns. In a test carried out with an OEM diaphragm pump on dosing 50ml using this method we generated a margin of error of 1-1.5%.
A key point to make in relation to this method is that it relies on a solid back-EMF signal in order to be able to accurately measure the range of dosing so it will not necessarily be suitable for applications where lower speeds are essential. Where you require lower speeds we would strongly recommend stepper motors and controllers as a method as they are much better suited to lower speeds. However, for pumps where stepper motors are not practical then this method is worth thinking about
If you have an application where you think using the methodologies described in this question would be useful (it may not be dosing specifically) then please get in touch with us to discuss your requirements and we would be very happy to help.
Is a brushless dc (bldc) motor and controller right for my application?
what do i need to think about when considering which brushless dc (bldc) motor and controller to use?
In order to know whether or not a Brushless DC motor is right for your application you need to think about several factors, some mechanical, some commercial and some of which will be down to your choice of brushless motor controller (sometimes also know as a brushless ESC or BLDC motor driver). Brushless applications tend to be higher speed, longer life applications but that doesn’t mean there aren’t alternative uses.
MECHANICAL FACTORS WHEN CONSIDERING BRUSHLESS DC MOTORS
BLDC Motors offer the highest speeds possible from any motor and have exceptional life. This is due quite simply to the absence of brushes within the motor which reduces friction (and therefore enables higher speeds) but also improves lifespan by removing the one part a brushed DC motor which will wear out with time and use. Bear in mind that the performance you can get from a brushless DC motor will also strongly be dictated by the brushless motor controller you choose to use. A low end BLDC ESC will deliver basic speed controls but may not be energy efficient or able to use advanced features such as back-EMF monitoring and constant speed adjustment whereas a more advanced industrial type BLDC Motor Driver such as the ZDBL15 can be optimised to be hugely energy efficient and also to maximise the mechanical performance of the motor.
An important point to consider if you are looking for specific qualities in a BLDC motor is that they are not generally known for positional accuracy or torque. If you need high torque you could add a gearbox but if positional accuracy is important you would be best looking at stepper motors
COMMERCIAL FACTORS – DOES USING A BRUSHLESS MOTOR AND BLDC MOTOR CONTROLLER MAKE FINANCIAL SENSE FOR MY APPLICATION?
Brushless motors are not the lowest cost motors on the planet but they are invariably the longest lasting. However, if your project is very price sensitive then a BLDC motor could still be achievable but it is likely that you would save money by using a brushed DC motor. If financial considerations are a major part of your considerations it is worth thinking about the lifespan of the project that you have as a brushless motor controller will last an average 5 times longer than a standard DC motor. If the cost of a brushless system is four times the brushed system but you need solid performance over a long lifespan then it is likely that the brushless motor system will be the most cost effective over the project lifetime.
A useful rule of thumb when selecting a motor for your project is that a brushed DC motor will typically operate well for 2000 hours whereas a brushless DC motor will operate well for 10000 hours. This obviously varies by manufacturer and motor type but if your application is likely to require regular and sustained use then a brushless DC motor and controller could actually be the most cost effective in the long run.
CONCLUSION – THINK ABOUT THE THINGS WHICH ARE MOST IMPORTANT FOR YOUR APPLICATION
Motor choice is rarely simple! The trade offs between life, performance and cost are something that needs to be taken into account when making the decision as well as the importance or value attached to key features such as constant speed under variable load. Think about which of these factors is most important to you before making a decision and if you require any advice at all please contact us and we will be more than happy to help
can i replace an existing dc motor with a brushless dc (bldc) motor?
The simple answer to whether brushed DC motor replacement with brushless motors is possible is yes.
Many companies are increasingly replacing DC motors with brushless DC motors in a wide range of applications. The main reasons for this is that BLDC motors and controllers offer improved lifespan, improved power density and improved mechanical performance.
In other words, they deliver more power from a smaller package, last longer and go faster!
THINGS TO CONSIDER WHEN SWAPPING A DC MOTOR FOR A BRUSHLESS DC MOTOR
The key to making the transition successful is knowing the performance characteristics and key specifications of the DC motor that you are wanting to replace and then being able to make a good match with a brushless DC motor.
This does not need to be an exhaustive list but a focus on torque and speed requirements as well as the physical dimensions of the shaft and motor body will usually suffice.
Always bear in mind you will also need to use a brushless motor controller or brushless ESC to drive the brushless motor so make sure you also have room for this within the space you need.
CHOOSING THE RIGHT BLDC MOTOR DRIVER OR CONTROLLER FOR YOUR APPLICATION
As mentioned above, with brushless motors you will need a brushless motor controller (sometimes known as a brushless ESC or BLDC motor driver) such as the ZDBL5 brushless motor driver in order to drive the motor.
This is because applying direct power to a brushless motor will simply lock it in one position. In order to make the motor turn you therefore require a motor, a controller and a method for telling the controller what you want it to do.
If you have been using a very basic DC motor then it is likely that you will simply want to apply a voltage and current and get the motor to turn at the speed and torque that it did before.
If this is the case, we can help.
Our engineers can custom programme the ZDBL Series to very closely match the performance characteristics of a previously installed DC motor. It does take a little time to get it right but once it is set up we will simply assign a part number and you can order the same pre-programmed controller at your leisure.
If this is what you are looking for then we strongly recommend that you contact us via email or online chat with a datasheet or part number of the motor that you want to replace. We will then review the best options available and get back to you with a proposal. Of course, if you have any questions at all about doing this please do not hesitate to give us a call.
FINER CONTROL OF THE MOTOR
However, if you are looking for something with finer control then using a brushless motor controller from the ZDBL Series will enable you to control the speed of the motor in a number of ways.
For example, the speed can be controlled by using external hardware such as pots or by using a 0-5v analogue voltage input (onto the brushless motor controller) or by using a range of communications protocols delivered from a PLC or other form of central controller.
It is worth re-emphasising the importance of the physical size of the motor in making the change as we have worked with some clients who have found the perfect motor specification from a torque and speed point of view but who have missed the fact that the brushless motor they had chosen had a 5mm shaft when they needed a 4mm shaft to make a direct replacement.
1mm difference can take up a huge amount of time and money so please do check. Beyond this focus on the key performance criteria of torque and speed and how you would like to control the motor. Once you have these specifications in place it is possible to source a similar brushless motor and use a brushless motor controller to drive it.
If you have any questions at all about what is best you can always contact us and we will be more than happy to help.
Quite simply, it’s about the hall effect sensors.
A sensorless brushless DC motor (sensorless BLDC motor) is quite simply a brushless DC motor without hall effect sensors. Hall effect sensors are sensors which are built into sensored brushless motors which are used to tell the brushless motor controller exactly where the rotor position is. This can be useful for maintaining set speeds and is particularly useful at start up as the rotor position dictates the start up sequence for the motor.
OPERATING A BRUSHLESS MOTOR WITHOUT SENSORS – THE IMPORTANCE OF SENSORLESS BRUSHLESS MOTOR CONTROLLERS
Based on the fact that the motor has no in built sensors then this means that the brushless motor controller has to operate the motor without the use of sensors. One of the ways this can be achieved is through using the back-
A brushless DC motor is actually very similar to a generator such as one might find in a dynamo or turbine and so as it is driven round by the BLDC motor driver it will also start to generate electromagnetic force. This then works against the forward voltage produced by the driver but crucially the frequency of the force is directly related to the speed of the rotor and can be measured by an intelligent sensorless brushless motor controller such as the ZDBL10. By using this back-
KEY ADVANTAGES OF A CLOSED LOOP SENSORLESS BRUSHLESS MOTOR SYSTEM
With an intelligent controller such as the ZDBL15 brushless ESC closed loop sensorless brushless motor systems can achieve impressive performance both in terms of accurate speed maintenance but also dosing performance in small brushless gear pumps or diaphragm pumps. Key to this is the fact that accurate back-
Of course, a further additional advantage is that sensorless brushless motors and BLDC motor controllers are also lower cost than Sensored Brushless Motors.
If you have any questions in relation to Sensorless Brushless Motors please feel free to contact us to discuss.
What is a sensored BLDC motor and what brushless motor controller (Brushless ESC) can I use with them?
sO, WHAT IS A SENSORED bldc MOTOR?
A sensored BLDC motor is a brushless DC motor with inbuilt positional sensors (called hall effect sensors). These sensors can be used by a brushless motor controller (brushless ESC) to monitor the exact position of the rotor and are therefore a useful method of maintaining speed of the brushless motor. These sensors are also particularly useful during the start up phase as it enables an optimised sequence to be applied depending on the exact position of the rotor.
A sensored brushless DC motor operates in closed loop as its standard operating method
THE ADVANTAGES OF USING SENSORED BRUSHLESS DC MOTORS
There are several major advantages of using sensored brushless DC motors. The core advantage of the sensored system over other similar systems is that they can reach much higher speeds and last much longer than most other types of motors (with the exception of sensorless brushless motors).
The second of these advantages is that they tend to be easier to setup and run than sensorless brushless motors. This is largely due to the sensors enabling the controller to know exactly where the rotor is and therefore to be able to operate accordingly. This initial knowledge of the rotor position removes many of the potential hurdles associated with sensorless brushless systems such as problems at startup and can also be used as a safety feature if required.
THE DISADVANTAGES OF USING SENSORED BRUSHLESS MOTORS
There are however, disadvantages to such motors.
Firstly, they are (generally speaking) more expensive than sensorless BLDC motors due to the added components and the additional complexity involved in construction. As a result of the additional complexity they are also more prone to problems, especially in applications where there are potential issues with humidity or dirt as any interference with the sensor’s performance will ultimately jeopardise the entire control of the motor.
What is the best controller to use with a sensored brushless motor?
Not surprisingly – a sensored BLDC motor controller! To browse our existing stock range please see our sensored brushless DC motor controllers here. We have several models which vary depending on the power requirement you have but also have features such as four quadrant motor control as optional extras.
Depending on your application it is also possible to drive your motor using a sensorless brushless motor controller.
I HAVE A SENSORED BRUSHLESS DC MOTOR, CAN I USE A SENSORLESS BRUSHLESS MOTOR CONTROLLER?
The simple answer is yes, although the sensorless brushless motor controller will clearly not be able to make use of the hall effect sensors.
A sensorless BLDC ESC or brushless motor driver such as the ZDBL10 will not be able to make use of the inbuilt sensors within the motor but it will still be able to drive the motor using a sensorless brushless drive. Speed can be accurately maintained by using the back-
If you are not sure about how this might impact on performance please contact us to discuss.
what is microstepping and how can it be used to improve stepper motor performance?
understanding microstepping is as simple as this:
A typical stepper motor has 200 steps to complete a 360 degree complete rotation (hence 1.8 degree stepper motors such as the ZDSPN17059). Full step mode would therefore enable a total of 200 positions in the 360 degree circle. Microstepping allows you take this further…
Microstepping is where a stepper motor controller is driven in a way that enables it to divide these steps up into further steps (or microsteps). These start at half steps but can go as high as 1/128 microsteps with the ZD Series of Stepper Motor Controllers.
This means that each of the 200 individual steps that are built into the motor have now been divided up into 128 separate steps by the controller. This enables the combined motor and controller to stop at anyone of 25600 possible positions around the 360 degree complete revolution.
MICROSTEPPING DOES NOT JUST DELIVER IMPROVED POSITIONAL ACCURACY…
When we first explain microstepping to some of our customers they assume that the main advantage of additional microstepping is that it delivers much greater positional accuracy for applications such as robotics or highly accurate dosing. However, there are a number of other additional benefits which can be derived from microstepping.
These include quieter operation –
REMEMBER MICROSTEPPING IS FASTER AND WHEN TO THINK ABOUT USING IT …
Don’t forget that, because microstepping is more energy efficient and uses smaller, more frequent pulses, it allows stepper motors to reach slightly higher speeds than they normally would. The trade-off here is that the torque of the motor is often reduced slightly as a result of this.
Based on the key points identified above it can be seen that the most appropriate applications for microstepping are those which either require exceptional positioning accuracy or those where energy efficiency and noise are important. In the majority of cases we would normally suggest using microstepping of some kind as it can usually lead to general improvements such as quieter and smoother operation but depending on the torque requirements of your project or application it is always best to discuss with one of our engineers first.
Using microstepping offers a large range of potential benefits depending on the nature of your application. From increased smoothness and positional accuracy to greater energy efficiency and speed. Why not browse our range of ZD Series Stepper Motor Drivers and see what they could do for your application today.
how do we compare a stepper motor driver and a stepper motor controller?
The first thing to understand with the comparison between a stepper motor driver and a stepper motor controller is that the terms are used rather interchangeably despite often being strictly incorrect.
As happens within many walks of life it is often quicker to refer to something as a ‘driver’ or ‘controller’ rather than a ‘combined stepper motor controller and driver’. (We are ourselves guilty of doing the same thing on this website for the sake of trying to make articles and descriptions easier to read).
LET’S UNDERSTAND THE TECHNICALLY CORRECT TERMS THEN
A stepper motor driver is an electronic component which can convert an input signal of some kind into movement of the stepper motor without itself being able to issue instructions (or control) the stepper motor.
It is often useful to consider the driver as a ‘translator’ between input signals and the physical movement of the stepper motor.
In some cases stepper motor drivers may be designed specifically to work with a set communication protocol such as analogue or CANbus but the broad principle is simple –
In contrast to this a stepper motor controller such as the ZD Series Stepper Motor Controllers can actively control and drive the motor itself. Strictly speaking such units should be referred to as a stepper motor driver and controller but it is perhaps understandable why people frequently shorten this down to stepper motor controller for ease of use.
A good visual example of this is probably the ZDLCD Series Stepper Motor Controllers. A stepper motor controller such as the ZD4LCD can quite clearly be seen to be both driving and controlling the stepper motor from the same unit.
The person using the controller puts in the instructions they need and the controller part of the unit then issues instructions to the driver part of the unit which converts the instructions into the physical sequences that the motor needs in order to turn.
CONCLUSION – A SLIGHT MINEFIELD
Hopefully you can now understand the basic differences between the two units in a technical sense and also understand why the terms are often a bit muddled in general use.
In simple terms the most important thing to understand is what you need for your project to work well and whether or not this is a stepper motor controller or driver.
If you have any questions about this you can always contact us to talk to one of our engineers or alternatively review some of our similar questions in the FAQs section.
Can a motor (and controller) maintain a fixed speed under variable load with stepper or brushless motors?
There’s never just one way with stepper or brushless motors.
There are several methods for maintaining a fixed speed under variable load with both brushless motors and stepper motors. These vary in accuracy and cost and choosing the best option for your project is best done on a case by case basis.
Using an Encoder, a Pot or Hall Effect Sensors
By using an encoder or pot on the back of a motor it is possible to actively monitor the exact speed of the motor and adjust it at any time to the speed required. This is called a closed loop system. An incremental encoder works by pulsing as the shaft turns and then sending these signals back to controller. This enables the controller to read the speed of the pulses and therefore accurately calculate the speed. An absolute encoder or pot works in a similar way but uses the variable resistance of the pot or the electromechanical construction of the encoder to enable the controller to calculate the absolute position of the shaft.
Hall effect sensors are largely used in brushless DC motors as a method for sensing the position of the shaft within the motor itself. These sensors are (perhaps rather predictably!) only found in sensored brushless DC motors and not in sensorless brushless DC motors. Bear in mind that sensored brushless DC motors can be driven by sensorless brushless DC motor controllers but that sensorless brushless DC motors cannot be driven by sensored brushless DC controllers…
All of these methods can be used to accurately judge the exact speed of the motor shaft and therefore make adjustments and can be used in both brushless motors or stepper motors (or indeed brushed DC motors). In all of these cases a change in the actual speed of the motor which was caused by an increase or decrease in load would be instantly picked up by an intelligent controller such as the ZD10 Stepper Motor Driver or the ZDBL15 Sensorless Brushless DC Motor Controller and the ZD10 or ZDBL15A could then be programmed to increase or decrease the power going into the motor to correct the speed.
Please note that in such systems safety features can become very important as there is obviously a cut off point at which the stepper motor controller or BLDC motor driver will not be able to deliver the power required to turn the motor if too much load is applied (ie the top power rating of the controller and/or motor). By having maximum current settings and other protective measures it is possible to protect the motor and controller by simply stalling the system and highlighting the error accordingly
Using Sensorless Brushless Motor Controllers that measure Back EMF
Speed monitoring and constant speed can also be achieved without encoders and similar devices by using a sensorless brushless motor driver (brushless ESC) such as the ZDBL10 sensorless brushless motor controller which can measure the back EMF from a brushless motor and therefore determine the speed of the motor and make adjustments accordingly.
Back EMF stands for Back Electro Motive Force and is a force generated by the action of the brushless motor turning. Because Back EMF frequency is directly related to the speed of the motor (it is similar to the way in which power is generated using a wind turbine for example) this frequency can be read by the BLDC motor driver and the speed of the motor calculated accordingly. It should be noted that this is generally a much lower cost option than using encoders and similar devices.
Deciding what the best option is for your application
The choice as to the best option for your specific project will depend on the constraints that you are working within. The back-EMF method of monitoring speed is usually the lowest cost solution but it does not operate particularly well at lower speeds. If your application does not generally need to be run at low speeds then this might well be the best option for you. However, if you wanted complete performance over the entire speed range then a system such as a sensored brushless motor might well be the best situation. Such a motor in tandem with an absolute positioning controller would represent a solid option
The nature of your application and the budget that you are working to will ultimately determine the most appropriate way to set your system up but the key thing to note is that there are several ways in which constant speed under variable load can quickly be achieved. Of these, using a sensorless brushless motor controller such as the ZDBL15 is probably the lowest cost and simplest but if you require a greater level of accuracy then it may well be the case that using an encoder or pot would be more beneficial.
the main advantages of using stepper motors
the many advantages of using stepper motors …
There are a huge number of advantages of using stepper motors over other types of motors in which stepper motors comprehensively outperform other types of motor. Conversely there are also performance areas that stepper motors are particularly poor at. However, for the purposes of this discussion we will explore some of the key advantages..
POSITIONAL ACCURACY IS AT ITS BEST WITH A STEPPER MOTOR
In general the main use of a stepper motor is in motor control applications where positional accuracy is hugely important. Whereas a ‘traditional’ brushed DC motor turns constantly as soon as enough power is applied, a stepper motor can be turned an exact number of steps (up to 25600 steps in one complete revolution with a stepper motor drivers such as the ZD2). Depending on the number of degrees per step in the motor (this varies from motor to motor but in a standard 200 step motor this equates to 1.8 degrees per step) this can then enable the motor to move from one fixed position to another fixed position at any point of the circle. By using intelligent controllers such as the ZD series drivers, this movement can then be controlled very accurately with programmable acceleration and deceleration curves being applied. This is especially useful in dosing or process control applications where exceptional accuracy is crucial
STEPPER MOTOR PERFORMANCE IS 90% DOWN TO THE CONTROLLER
The way in which a stepper motor performs and is able to operate is clearly heavily influenced by the build quality of that particularly motor. Conventional factors such as the quality of the bearings and magnets used are still of great importance. However, in terms of delivering the true potential of the stepper, it is the controller that can really make a difference.
As an example a simple stepper motor driver will simple convert an input current and voltage into motor torque and speed. Compare this to a comprehensive ‘all in one’ stepper motor driver and controller such as the Zikodrive ZD4 Stepper Motor Controller which has onboard memory, 128 microstepping and full programmability. With the ZD4 Stepper Motor Controller being used it becomes possible to directly control the stepper motor position, its acceleration and deceleration curves, custom startup sequences, the exact speed and torque and to store these settings within the controller. This enables the motor to be completely optimised and opens up a whole new world of potential mechanical performance and applications.
ALTERNATIVE APPLICATIONS FOR STEPPER MOTORS
Whereas a brushless DC motor and controller would require careful calibration, timing and the use of encoders and limit switches to rotate a prism 120 degrees, wait a set time and rotate another 120 degrees, with a stepper motor this can be achieved relatively simply because it is possible to measure the exact number of steps required to make this movement and use an intelligent controller to make this movement.
If one considers more complex applications such as robotics or highly accurate dosing equipment then one can appreciate how useful having this level of control would be. By adding a controller capable of microstepping such as the ZD4 Stepper Motor Driver (this offers up to 128 microsteps) it is possible to gain exceptional positional accuracy. Based on a standard 1.8 degree 200 step motor, the ZD4 Driver can move accurately between any of 25600 points of a circle.
CONCLUSION – COMPLETE MOTOR CONTROL
Fundamentally, it can therefore be the key advantages of steppers is that they enable the motor to stop and start at any point required with exceptional accuracy. In combination with an intelligent motor controller it is possible to achieve exceptional positional accuracy and performance from a stepper motor that is quite simply unachievable with any other type of motor
how to replace a brushed dc motor with a stepper motor
an emerging trend in the motion control industry
If you want to replace brushed DC with stepper motor then this is perfectly possible but there are one or two things you will need to be aware of before attempting this.
You can find out more about this by reading our article on replacing brushed DC motors with brushless motors.
However, swapping DC motors to stepper motors and controllers is less common. That said, as with lots of things in life and in engineering, just because something is not common, does not necessarily make it a bad idea. There are a number of specific applications in which replacing a brushed DC system, (particularly a geared DC system) with a stepper motor and controller can be a very sensible choice
WHY SHOULD I REPLACE A BRUSHED DC MOTOR WITH A STEPPER MOTOR?
The simple benefits of doing so are that you will improve the lifespan of the system you have (stepper motors only have bearings as parts that can wear out as opposed to brushes).
Stepper motors also improve the range of performance options available (they can turn a fixed number of degrees easily).
REPLACING GEARED DC MOTORS WITH STEPPER MOTORS AND CONTROLLERS IN DOSING APPLICATIONS
What is more common is to replace geared brushed DC motors with a stepper motor in applications such as pumps, lab equipment and similar applications where positional accuracy can be improved vastly by using a stepper motor and stepper motor controller.
Many applications were addressed in years gone by by using a geared DC motor and timing as a means of dosing and measuring –
Of equal importance, the cost of such technology has dropped considerably in recent years, making advanced performance options affordable to a broad range of applications.
Whereas 10 or 20 years ago a programmable stepper motor controller would have cost a fortune, these days it is much less.
The result of this trend is that many people and companies have started to look at replacing geared brushed DC motors with stepper motor controllers as a means of improving the performance of the system and also as a way of adding more features.
DON’T FORGET TO DO YOUR HOMEWORK
The key to being able to replace brushed DC with stepper motor successfully is making sure you know the performance characteristics and key specifications of the motor that you are wanting to replace and then being able to make an appropriate match with a stepper motor and controller. If you are not sure how to find out the performance characteristics of the motor (and gearbox) that you have you can start with the part number of the motor and research that. Key characteristics to look for are max and nominal RPM and torque.
Once you have these details you then need to source an appropriate stepper motor with the right performance characteristics. Don’t forget to check the torque speed curve of the motor to make sure it will deliver the torque you need at the speed you want (if you are not sure about this you can find out more about this by reading our guide to understanding torque speed curves). If you have any questions at all about implementing this system then you can always contact us and talk to one of our engineers about your specific project or application.
If you have an existing project where you are looking to replace a DC motor with a stepper motor and controller you could start by having a look at our online shop where we have a range of stepper motors, stepper motor controllers and recommended motor and controller packages.
If you have any questions about anything that you have read above please feel free to contact us to discuss.
Generally speaking the top speed of a stepper motor is approximately 1000rpm. The exact speeds that are possible depend on the specific motor being used and the controller being used with it. For example it is possible to overdrive a smaller stepper motor with a higher powered controller but this will result in reduced life span and any of the benefits of doing so will largely be minimal in comparison to using a brushless DC motor at the rated speed. It is important to remember that the torque generated by a stepper motor is significantly reduced as the speed increases.
If you would like more information on torque speed curves and how they can help you choose the best motor for your project then please see What is a torque/speed curve and how does it affect what I need?
If you need to go above this speed but still require intelligent control of the motor you should consider a brushless DC motor and controller (brushless ESC).
STEPPER MOTORS HAVE DECREASING TORQUE AS THE SPEED INCREASES
A point which is often overlooked is the fact that the available torque from a stepper motor decreases significantly as the speed increases. This often means that in applications where the motor is under a certain load (which it obviously has to be as it is driving something) the max speed will be inherently reduced by the amount of load on the motor. This is why it is so important to understand the load that you need to place on the motor when choosing a motor.
I NEED A LOWER SPEED AND A HIGHER TORQUE FROM A STEPPER MOTOR
If you need a lower speed and higher torque to make your motor control project work do not forget that you can always use geared stepper motors. Gearbox ratios typically range from 2:1 up to about 50:1 and this can dramatically increase the torque available from the stepper motor (albeit at the cost of significantly reducing the maximum speed available from the stepper motor). For example, a typical NEMA 17 stepper motor with a ZDSP Stepper motor driver will be able to achieve 0.65Nm of torque. However, by adding a gearbox to this motor – such as in the case of the ZDSPN17B27-3 geared stepper motor and driver package this can be increased up to 3Nm.
CONCLUSION – THINK ABOUT THE KEY SPECIFICATIONS THAT YOU NEED AND THEN DECIDE WHICH MOTOR AND CONTROLLER IS BEST FOR YOUR APPLICATION
The maximum speed of a stepper motor is dictated by a combination of stepper motor size, the type of stepper motor controller that it is being used with and also the specific application that it is going into. All of these factors need to be considered when assessing how much speed you can realistically achieve for a set application or package.
If you have any questions at all about this please feel free to get in touch with us to discuss your requirements with one of our engineers.
NEMA MOTOR FRAME SIZES AND WHAT THEY MEAN…
Always remember that (within the NEMA sizing system) the length of the motor will vary but the NEMA frame size simply refers to the diameter of the motor face.
Most commonly these faces are square (for example the ZDN2319 which is a square faced 1.9Nm NEMA 23 stepper motor) but in some cases they may be circular.
Frame sizes are split up into NEMA (National Electronic Manufacturers Association) ratings which are a useful shorthand for motor sizes.
DIAMETER ISN’T EVERYTHING WHEN IT COMES TO STEPPER MOTOR POWER
Changing the stack length will generally not impact on the speeds that you can get but it will have a major impact on the torque (turning force) that you are able to achieve.
For example the ZD2N2318 and ZD10N2318 stepper motors are both NEMA 23 motors (therefore 57mm diameter) but the ZD2N2318 is 42mm long whereas the ZD10N2318 is 104 mm long.
The difference in torque between the 2 motors is 0.6Nm for the ZD2N2318 and 2.4Nm for the ZD10N2318. The difference in stack length of a motor with the same NEMA rating has therefore quadrupled the possible torque.
THE STEPPER MOTOR CONTROLLER YOU CHOOSE MATTERS!
Equally the stepper motor controller that you use will have a major impact on the mechanical performance you are able to achieve using the motor. If the controller is not able to deliver more power than the motor can handle then it is unlikely that you will be able to achieve the maximum possible mechanical performance from the motor.
As an example of this, our stepper motors with integrated controllers have higher powered controllers the bigger the motors get.
See the table below for an overview of frame sizes.
MOTOR FRAMES AND TYPICAL SPECIFICATIONS FOR STEPPER MOTORS
If your interest in motor sizes was purely academic then we hope we have helped. If you have any questions about this please do not hesitate to get in touch and we will do our best to help.
Alternatively if you are looking for a motor and aren’t sure which is best for your application then you could start by having a quick look at our standard range.
We offer a range of stepper motors of different sizes which are available in geared or standard format.
As always, if you have any questions about choosing the right motor or the pros and cons of a long stack NEMA 17 versus a short stack NEMA 23 (for example) then you can get in touch with us via online chat, phone or email.
SIMPLE POTS, SWITCHES AND BUTTONS?
Depending on your requirement there are a number of potential motor control interface options which can offer simple or more in depth control as required.
Potentiometers and buttons/switches are the simplest form of user interface which will work with the Zikodrive range of stepper motor controllers and brushless ESCs. In combination with the programmability of all of our controllers these can be set up to operate in pretty much whatever way you might want. Typical methods usually involve having a pot as a speed control and buttons for stop/go and forward/reverse but we have sometimes added additional controls for features such as current control and microstepping. The simplest thing to do if you have something slightly more customised in mind is to give us a call or an email and we will tell you what we can do.
STEPPER MOTOR CONTROLLERS OR BRUSHLESS ESCS WITH LCD DISPLAYS AND VISUAL INTERFACES
Not all of our controllers can be set up to work with LCD displays but the ZDLCD series of stepper motor controllers shows what can be done by adding an LCD screen. Again, there are virtually limitless options available in terms of screen sizes, resolutions etc. and everything can be custom set up to what you require. If you have something specific in mind or something that you would like to work with your project please just ask.
To see a specific case study example of how we can develop this type of system you can view the Boxer Pumps iD Stepper Motor Controller Case Study.
To discuss your requirements in more detail send us a message or give us a call today.
Let’s start with a single shaft
Quite simply a single shaft motor (such as the ZDN2319 1.9Nm stepper motor) has one shaft which comes out of the face of the motor and a dual shaft motor has the shaft coming out of the face and rear of the motor.
The single shaft is a straight forward concept which can be easily understood – namely that the motor is driven by a controller and the shaft is then connected to the required part of the application.
What on earth would I want with two shafts?
It’s a very good question!
The dual shaft can be used in a number of ways. One example is to drive 2 applications on either side of the motor. A second (and by far the most common) is to use the rear shaft to mount an encoder, brake or hall sensor array in order to be able to set up a closed loop speed control system.
Depending on your specific requirements these add-ons can then be used without having an impact on the main drive shaft. For example an encoder can be used to turn an open loop stepper motor system into a closed loop system.
How do I choose the best option for my application?
The starting point is to think about the space that you have available to you and how important closed loop speed monitoring is for your project.
If closed loop speed monitoring is essential for your application then it is possible that a dual shaft motor could be a good option. However, there are other factors that need to be considered first – for example the overall torque and speed requirement of the motor. If this is quite high then a brushless DC motor might be the best option – in which case it is possible to run a basic closed loop system using a sensored brushless DC motor.
If in doubt, talk to an expert!
If you’re still not sure what the best option is for your particular project then we would invite you to talk directly to our team who are happy to advise.
Click here to contact us directly or please talk to our UK sales team using the online chat facility.
find the right motor controller for your motor …
got a motor in mind?
If you have already chosen a motor for your application then you should have a good starting point with the electrical specifications of the motor. It is always best to choose a controller which has more power than the motor rating as using a controller with less power can often result in damage to the controller and will also not get the full mechanical performance range from the motor. Once you have looked at the motor drivers which meet your electrical requirements it is then time to think about which motor controller features you require.
NOT CHOSEN A MOTOR?
If you haven’t chosen a motor why not read out FAQ post on Choosing A Motor. This section is designed to highlight some of the most important issues which arise when choosing a motor and will then lead on to how to select the right brushless motor controller or stepper motor controller for your specific application.
CASE STUDY: ZIKODRIVE ZDSP STEPPER MOTOR CONTROLLER VS ZIKODRIVE ZD2 STEPPER MOTOR CONTROLLER
For this example, let’s assume you have picked a small NEMA 23 stepper motor which outputs 0.65Nm torque and requires an input current of 1.5A at 12v. Both the ZDSP Stepper motor Controller and ZD2 Stepper Motor Controller can handle this power level but they have different features which may have an impact on your choice. The ZDSP offers microstepping up to 1/16th microsteps whereas the ZD2 Stepper Motor Controller can go up to 1/128th microstepping. The ZDSP Stepper motor Controller features a 24 bit speed resolution whereas the ZD2 has a 20 bit speed resolution.
In practice the key to making the right decision is to prioritise the performance features which are most important to your specific motor control application. If you needed exceptional positional accuracy and smoothness from your motor then the ZD2 Stepper Motor Driver would be the most useful. However, if finding and maintaining an accurate speed was the most important factor then you would be better with the ZDSP Stepper Motor Controller.
ARE THERE ANY PHYSICAL RESTRICTIONS WHICH COULD IMPACT ON YOUR CHOICE OF MOTOR CONTROLLER?
You will hear us say this a lot but never forget to check the physical sizes of a stepper motor controller or brushless ESC and think about how this might impact on your application or how you might fix the controller in its particular location. Some controllers such as the ZD Series Stepper Motor Controllers have been designed to be mounted onto specifically sized stepper motors but other controllers may have been designed to be mounted ‘in line’ or fixed in DIN Rail Casings.
In addition remember that certain controllers can need heat sinking or clear air flow around them so make sure you have enough space to achieve this. If in doubt you can always give us a call and select option 2 on the initial menu to talk to someone in our technical team.
FIRST THINK ABOUT BASIC POWER REQUIREMENTS THEN THE CONTROL FEATURES YOU NEED IN A MOTOR CONTROLLER
Electrical and power ratings are fundamentally the most important factors. After that, think about what key performance features you are looking for from a motor controller. If you are looking for some practical examples of how to match stepper motor controllers to NEMA 17 and NEMA 23 stepper motors then why not view some of our stepper motor packages?
A torque/speed curve plots the torque of a motor against the speed the motor is going at. The relationship between speed and torque varies dramatically across different types of motor and also between manufacturers. In part this is a result of the mechanical design of the motors in question but in other cases, choice of materials and manufacturing tolerances may be relevant.
The relationship between the torque and the speed is critical to choosing the right motor for your application.
Given that the amount of torque available changes with a change in speed it is important to think about the performance point you need when selecting a motor and controller.
A common mistake is to buy a motor based on its rated or holding torque (thinking this is perfect for your application) only to find that this torque is not available at the required speed.
If you’re not sure what motor and controller is best for your application – give us a call on +44 (0) 333 1237130
Consider the torque/speed curve (below)for a typical stepper motor;
The ZD Series of Stepper Motor Controllers can be run using a range of external inputs, offers 25600 potential positions (on a standard 200 step stepper motor) and can be programmed to do virtually anything! However, as the above torque speed graph highlights, an increase in speed leads directly to a drop off in the torque available from the motor and controller.
Depending on the torque and speed that you require for you application, we can supply the ZD Series of Stepper Motor Controllers with a range of stepper motors giving you plenty of choice!
WHAT HAPPENS TO THE AVAILABLE TORQUE AS THE SPEED INCREASES CAN BE VERY DIFFERENT FROM MOTOR TO MOTOR
As you can see in the example above the torque at lower rpm is very high but as the speed builds within the motor, the torque begins to drop away. In many respects this can be seen as a resultant trade-
It is important to bear in mind that different motors will have unique torque speed curves and also that with stepper and bldc motors, the controller used will also directly affect the torque speed curve. The key to using torque/speed curves is therefore to understand the exact or minimum requirements that you need from a motor and use the torque speed curve to make a much more accurate assessment of the motor and controller that you need.
THE IMPORTANCE OF THE STEPPER MOTOR DRIVER OR STEPPER MOTOR CONTROLLER WHEN USING A STEPPER MOTOR TORQUE SPEED CURVE
When viewing a stepper motor torque speed curve such as the one above it is common to see an explanation at the top of the diagram which will explain what controller was used in the measuring of that particular curve. Different stepper motor controllers can output different levels of power and it may be the case that the motor you are looking at could output more power if it was used with a higher powered stepper motor controller. Equally it is also important to bear in mind that a stepper motor controller set on full step will typically generate a higher torque than a stepper motor controller running a microstepping sequence so if you are thinking of utilising a microstepping programme then it is worth contacting us first to discuss.
A USEFUL GUIDE TO WHAT YOU CAN EXPECT FROM A MOTOR
The torque speed is a fundamental guide to what you can expect to get in terms of mechanical performance but it is important to understand the specific situation in which a torque speed curve was created in order to ensure it meets your expectations. If you have any questions at all about torque speed curves and how they might affect your choice of motor then please don’t hesitate to contact us via online chat or phone and we will be more than happy to help.
choosing a motor for your project or application
what’s the starting point?
The first port of call when choosing a motor is to understand what torque and speed you require. This will immediately give you a clear idea of what is possible. As a quick example, most stepper motors do not exceed 1000rpm.
Therefore if you need to go above this you will need a brushed DC or brushless DC motor. Equally if you require positional accuracy or easy monitoring of number of revolutions for an application such as dosing or pumps, then a stepper will perform much better.
SELECTING THE MOST IMPORTANT FEATURES AND PERFORMANCE CRITERIA YOU REQUIRE IN A MOTOR
The second port of call is to understand what you require from the motor for it to work successfully in your application and the extent to which each type of motor might be able to achieve this? For example, ask yourself the following questions;
1. Do you need high positional or speed accuracy?
2. Is energy efficiency and lifespan a high priority?
3. Do you need to maintain a constant torque or constant speed?
If you require high positional accuracy stepper motors are by far the best choice as they can be micro-
CONCLUSION – NARROW IT DOWN USING BASIC PARAMETERS AND THEN PRIORITISE THE KEY FEATURES THAT ARE MOST IMPORTANT TO YOU
Fundamentally there are applications where one type of motor will be the obvious choice –
How does back-EMF control of sensorless brushless motors work and what brushless motor controllers do I need to use this?
what exactly is back emf?
Back EMF stands for Back Electromotive Force. In simple terms, the Back EMF is an electromotive force which occurs as the brushless motor turns. This acts like a generator creating electromotive resistance within the motor. Critically, motor controllers such as the ZDBL15 can measure the back-EMF generated. As the back-EMF frequency is proportional to the motor speed this enables us to determine the exact speed of the motor.
An intelligent motor controller such as the ZDBL15 sensorless brushless motor controller can then read this force and use it to measure the actual speed of the motor. The ZDBL15 can then maintain this speed using Back EMF as a reference to measure and adjust the speed. It is this method which enables a sensorless brushless motor controller such as the ZDBL15 to be able to deliver constant speed under a variable load.
ARE THERE DISADVANTAGES TO USING BACK EMF IN SENSORLESS BRUSHLESS MOTOR CONTROLLERS?
No back EMF is generated when the motor is stationary, meaning that start up is difficult. As such, the motor can take a small amount of time to settle and run efficiently. A second disadvantage is that at low speeds the back EMF is weak and therefore quite difficult to measure accurately. This can result in inefficient operation in the form of jumpiness. Stepper motors are perfect if your application needs reliable operation at low speeds.
WHAT ARE THE MAIN ADVANTAGES OF USING BACK EMF IN THE CONTROL OF SENSORLESS BRUSHLESS MOTORS?
If you have any additional questions please CONTACT US to discuss.