Bldc hall sensor placement

Remember Me? BLDC motor controller- Hall sensor placement. Is there any formula connecting the two? It was observed that speed reduced with increse in angle.

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But i couldn't understand why. Is it because of the programming done in the controller? How exactly is speed calculated from three hall sensor output combination through programming? So the sensor placement position affects the speed. I've done experiments building a BLDC motor from a 3-magnet spinning toy, powered by a coil of wire, photosensor and 2 transistors. A motor under load wants to stall.

This cannot be permitted. Motion must be maintained. The magnet needs to be pulled along from coil to coil. Thus we ought to sense when a magnet is at a certain distance from a coil, where it 'does the most good' to energize the coil and attract the magnet. That is how to maximize torque and maximize efficiency. Mine is not an expert answer. An expert might reply and tell what sensor positions give best results: either a detecting which coil has a magnet nearby, so that we know which coil to turn on.

Or b to detect location of a magnet between coils, so we know at what point to turn on a coil. Is it possible to switch a 3 phase bldc with 2 hall sensor? What is the programming logic? How can you prove it? Can u explain the logic behind it. Using three digital hall sensors is the usual scheme because it allows a simple direct relation of sensor signal to motor control.

With only three digital sensors you can't determine the initial position exactly and don't achieve optimal starting torque. Generating three phase motor voltages based on two sensors isn't completely impossible but involves a large software overhead.

It's not simple switching logic but estimating rotor position and speed and generating switch events based on this information. In any motor, to generate Torquethe rotor's magnetic field should be at right angles with the stator's magnetic field. Torque is what rotates a motor, all the other motor quantities derive from it. In a conventional DC motor, the commutator does that for you.

In an induction AC motor, the field induced on the rotor automatically does that for you. But in a BLDC, you have to synthesize it. Since the rotor will attempt to align itself with the stator, causing the rotation, you will have to continually and dynamically adjust the rotor's field for the motor to continue rotating.

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Thus you have to know at all times the rotor's angular position. This is done at a minimum, with a quadrature encoder, which tells the DSP microcontroller the rotor's Cartesian coordinates.

How Hall Sensor Works in Brushless DC Motor?

The DSP, from that information and the user's commands, will then synthesize the rotating magnetic field by continuously changing the vector sum of three-phase voltages.

You have to study basic electrical motor theory, and its control methods. There is no other way you will fully understand. In these days, it is as simple as doing a Goggle search.By using our site, you acknowledge that you have read and understand our Cookie PolicyPrivacy Policyand our Terms of Service.

Electrical Engineering Stack Exchange is a question and answer site for electronics and electrical engineering professionals, students, and enthusiasts. It only takes a minute to sign up. I know that there will be there hall sensors in a BLDC hub motor. They are placed in such a way that they could detect the poles of the rotor magnets, and two of these sensors always read one pole while the other contradicts. But how is it engineered to place these hall sensors. What is the mathematical calculation behind it?

The following image shows the most simple BLDC motor with just one pair of coils and a rotor with two poles, at the moment when polarity is changed:. The hall sensors of these BLDC motors often already contain a comparator giving a high or low level, indicating if they see a N or S pole.

In the example above, such a sensor would be placed where the blue triangle is. The electronics behind would make it so that the polarity of the e-magnet on the right is always the same as what the sensor sees.

You'll find this principle in that fans used in computers, though there are two pairs of coils and the rotor has four poles:. Note that the sensor is placed so that it sees the transition when the poles of the rotor are exactly aligned with the coils! In the most basic mode of operation, each pair of coils changes its polarity when the rotor poles are aligned to it, i. In reality, it's more complex, see the source. So you could use three hall sensors in there, each responsible for one pair of coils.

So, now it depends on the design of the motor - how many coil pairs are used, and how many poled does the rotor have. With some logic or some intelligence of the controller, it is also possible to spare some sensors. Sign up to join this community. The best answers are voted up and rise to the top. Home Questions Tags Users Unanswered. Asked 3 years, 8 months ago.

Active 3 years, 8 months ago. Viewed 4k times. Or Is it just trial and error? Aswinth Raj Aswinth Raj 31 1 1 silver badge 5 5 bronze badges. Active Oldest Votes. The following image shows the most simple BLDC motor with just one pair of coils and a rotor with two poles, at the moment when polarity is changed: From left to right: The e-magnets still attract the the poles the permament magnet of the rotor and create torque The polarity of the e-magnets changes The e-magnets repel the poles of the stator facing them and attract the poles on the opposite side, creating torque The hall sensors of these BLDC motors often already contain a comparator giving a high or low level, indicating if they see a N or S pole.

You'll find this principle in that fans used in computers, though there are two pairs of coils and the rotor has four poles: Source Note that the sensor is placed so that it sees the transition when the poles of the rotor are exactly aligned with the coils!

Another type of motor uses a rotor with two poles and three pairs of coils: Source In the most basic mode of operation, each pair of coils changes its polarity when the rotor poles are aligned to it, i. Sign up or log in Sign up using Google. Sign up using Facebook.The advantages of a brushless motor over a brushed motor are the high power to weight ratio, high speed, and electronic control. Brushless motors find applications in such places as computer peripherals disk drives, printershand-held power tools, and vehicles that range from model aircrafts to automobiles.

Like all other motors, BLDC motors also consist of a rotor and a stator, which can be seen in Figure 1. The BLDC motor stator is made from laminated steel stacked up to carry the windings. BLDC motors are controlled using electrical cycles.

One electrical cycle has 6 states. The Hall sensor based motor commutation sequence is showed in Figure 2. In the case of a brushed DC motor, feedback is implemented using a mechanical commutator and brushes. In a BLDC motor, feedback is achieved by using multiple feedback sensors.

The most commonly used sensors are Hall sensors and optical encoders. Within a 3-phase BLDC the number of teeth poles is a multiple of 3 and the number of magnets is a multiple of 2. Depending upon the number of magnets and teeth each motor has a different number of cogging i. To calculate the number of steps N we need to know how many teeth and how many magnets are used in the motor. The motor used in this application note has 12 teeth poles and 16 magnets.

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The main block diagram and typical application circuit are shown in Figure 3 and Figure 4 respectively. This design has 2 inputs to control motor speed and direction.

What is a BRUSHLESS MOTOR and how it works - Torque - Hall effect - 3D animation

PIN 2 is used to control speed via an input frequency. The absence of the frequency signal on this pin will turn off the driver and the motor will stop. Applying frequency to this pin will start the motor during the first ms. Using an input frequency allows us to control the motor speed very precisely. To calculate RPM we need to know how many electrical steps a motor contains:.

The motor within this application has 48 steps, so at a frequency of 5kHz the motor will run at RPM. An internal Vref component, set at 1. The input frequency clocks these DFFs and sets the rotation speed.

The result is that the output alternates in level each time any Hall sensor changes its polarity. Both edge detectors generate the actual speed frequency Hall frequency which is compared with input frequency to generate a PWM signal to control the speed of rotation. The motor is stopped until the input frequency to PIN2 is applied.The brushed DC motor adopts the electric brush and the commutator to realize commutation of the current in the winding.

On the contrary, the BLDC motor realizes commutation of the winding current in the electronic way. Commutation of the BLDC motor is controlled electronically.

To ensure the BLDC motor to move, the stator winding should be powered on according to certain sequence. In order to identify which winding will gain electricity first according to the electrification sequence, it is important to know the rotor's position, which is detected by the Hall sensor embedded in the stator.

When the rotor magnetic pole passes nearby the Hall sensor, it will give out a high level signal or a low level signal, indicating that the north magnetic pole or the south magnetic pole is passing by the sensor. According to the combination of the three Hall sensor signals, the precise sequence of commutation can be pinned down. The torque of the DC electric motor react with the current in the winding via the permanent magnetic field.

In the brushed DC motor, the commutator realizes commutation of the armature current and seeking of a suitable magnetic field by switching to the armature current. In the BLDC motorthe Hall sensor detects the position of the rotor's rotating magnetic field and provides the corresponding winding excitation through the logic and driving circuit. On the whole, the winding responses according to the magnetic field of the electric motor's permanent magnet, thus generating the required torque.

bldc hall sensor placement

Brushless DC motor braking is usually fast braking by motor itself. There are two simple methods. One is energy consumption braking, the other is short connection braking. Energy consumption braking Water ions have the function of protecting hair, the hair dryer treats water molecules in air to ultrafine particles and improve the water We can Sine Wave Control of Brushless DC Motor Sine wave control of brushless DC motor means that the motor winding generates the sine-wave current through exerting a certain voltage to the motor winding, so as to realize the purpose of Because of Y-shaped connection of BLDC motor, three phases are connected to the public neutral points, resulting in failure of the phase voltage to be directly measured.

As a result, only the Get a Price Sitemap.By using our site, you acknowledge that you have read and understand our Cookie PolicyPrivacy Policyand our Terms of Service. Electrical Engineering Stack Exchange is a question and answer site for electronics and electrical engineering professionals, students, and enthusiasts. It only takes a minute to sign up. I have a BLDC hub motor out runner type; 3 phase wires for my electric bike.

It currently has 1 set of hall sensors 3 pieces and I would like to install a second set 3 more for spare in case one of the original 3 stops working. Current hall sensor's locations: NOTE: on the photo the middle hall sensor is not installed since the photo was taken when replacing it with a new hall sensor. In the following picture I have tried to indicate which wires serve which purpose: The wires indicated in red are the motor phase wires The hall sensor-wires indicated in green in the picture go from the outside of the motor top right in the picture to the PCB green circle in the picture and via traces in the PCB the wires go to the 3 hall sensors.

Color coding:. Photo from slightly different angle:. There is also 1 wire for a temperature sensor among the wires inside the green circle but Its currently not connected.

There are hub motors which come with 2 sets of hall sensors from the factory and I would like to upgrade mine to 2 sets. I was wondering where I should put the new set of hall sensors in order for the motor's timing of the different coils to remain unchanged in other words so that I don't mess up the motor's timingboth sets of hall sensors have to be activated at the same time such that if i were to connect them in parallel hall sensor A set 1 to hall sensor A set 2 they would only give 1 signal if that explanation makes any sense.

Is my only option to either place the new hall sensors on top of the existing hall sensors not sure if i have enough room for this or to place the new hall sensors on the other side of the motor current set of hall sensors are placed on top of the windings on the right side of the bicycle when the motor is insertedI could perhaps place the new set of hall sensors on top of the windings on the left side of the bicycle.

Any other better suggestions for placement of second set of hall sensors are definitely welcome. You can place the other three Hall sensor in the next groove: That is: you rotate each Hall sensor clockwise or counter colckwise doesn't matter. The Hall sensors are needed to detect the commutation instant.

The important thing is that the sequence be maintained, so the relative position and not the absolute position is the important thing.

Sign up to join this community. The best answers are voted up and rise to the top. Home Questions Tags Users Unanswered. Where to place hall sensors BLDC motor? Ask Question. Asked 1 month ago. Active 1 month ago. Viewed 58 times. The current set was installed from the factory. Maarten -Monica for president. Maarten -Monica for president Maarten -Monica for president 6 6 bronze badges.

What about the device covered with black rubber and black cable? What's that for? I replaced the middle hall sensor some time ago, unfortunately I don't recall part number, will try and find a photo.By using our site, you acknowledge that you have read and understand our Cookie PolicyPrivacy Policyand our Terms of Service.

Electrical Engineering Stack Exchange is a question and answer site for electronics and electrical engineering professionals, students, and enthusiasts. It only takes a minute to sign up. I know that there will be there hall sensors in a BLDC hub motor.

They are placed in such a way that they could detect the poles of the rotor magnets, and two of these sensors always read one pole while the other contradicts. But how is it engineered to place these hall sensors. What is the mathematical calculation behind it? The following image shows the most simple BLDC motor with just one pair of coils and a rotor with two poles, at the moment when polarity is changed:. The hall sensors of these BLDC motors often already contain a comparator giving a high or low level, indicating if they see a N or S pole.

In the example above, such a sensor would be placed where the blue triangle is. The electronics behind would make it so that the polarity of the e-magnet on the right is always the same as what the sensor sees. You'll find this principle in that fans used in computers, though there are two pairs of coils and the rotor has four poles:.

bldc hall sensor placement

Note that the sensor is placed so that it sees the transition when the poles of the rotor are exactly aligned with the coils!

In the most basic mode of operation, each pair of coils changes its polarity when the rotor poles are aligned to it, i. In reality, it's more complex, see the source. So you could use three hall sensors in there, each responsible for one pair of coils.

bldc hall sensor placement

So, now it depends on the design of the motor - how many coil pairs are used, and how many poled does the rotor have.

With some logic or some intelligence of the controller, it is also possible to spare some sensors. Sign up to join this community. The best answers are voted up and rise to the top. Home Questions Tags Users Unanswered. Asked 3 years, 7 months ago. Active 3 years, 7 months ago. Viewed 4k times. Or Is it just trial and error? Aswinth Raj Aswinth Raj 31 1 1 silver badge 5 5 bronze badges.

Active Oldest Votes. The following image shows the most simple BLDC motor with just one pair of coils and a rotor with two poles, at the moment when polarity is changed: From left to right: The e-magnets still attract the the poles the permament magnet of the rotor and create torque The polarity of the e-magnets changes The e-magnets repel the poles of the stator facing them and attract the poles on the opposite side, creating torque The hall sensors of these BLDC motors often already contain a comparator giving a high or low level, indicating if they see a N or S pole.

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You'll find this principle in that fans used in computers, though there are two pairs of coils and the rotor has four poles: Source Note that the sensor is placed so that it sees the transition when the poles of the rotor are exactly aligned with the coils! Another type of motor uses a rotor with two poles and three pairs of coils: Source In the most basic mode of operation, each pair of coils changes its polarity when the rotor poles are aligned to it, i.

Sign up or log in Sign up using Google. Sign up using Facebook. Sign up using Email and Password. Post as a guest Name.In some categories of motor drive applications, users have little or no tolerance for unpredictable, uneven, or irregular motor behavior.

While this certainly cannot be said of all motor-driven products — electric toothbrushes, for instance, or battery-powered toys maintain a tight focus on bill-of-materials BoM cost and will almost always accept a small amount of erratic motor behavior as a reasonable trade-off for minimizing the cost of the motor — other motor drive applications demand a superior level of operation.

Power tools are an example of a product type in which reliable and predictable motor performance is an absolutely essential feature. Counting against the brushed DC motor, however, are its relatively low efficiency and the inherent tendency for the brushes to fail before other components due to mechanical wear or chemical contamination.

The main challenge for the designer of a BLDC motor control system is that the motor suffers from hiccupping and inconsistent torque and acceleration, when the commutator is forced to operate in the absence of accurate and real-time absolute rotary position data.

Absolute position sensing has, in the past, only been available from extremely expensive sensors: The lower-cost sensing solutions suitable for the BoM budgets of most motor system manufacturers have not met this requirement adequately. In power tools and other performance-critical end products, then, efficient and reliable BLDC motor technology has generally not found favor.

This article suggests, however, that power tool manufacturers and others with similar requirements could adopt the BLDC motor by taking advantage of a semiconductor product type — the magnetic position sensor IC — which, along with a simple magnet, provides absolute position data, comes at a low system cost, is easy to assemble into a motor system, and enables a BLDC motor to maintain optimal commutation at all times.

A BLDC motor control system has to provide clean start-up operation, maintain continuous commutation, achieve the highest possible efficiency, and extract maximum torque from the available electrical power.

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The key to achieving all of these goals is knowledge of the position of the rotor relative to the stator, information which enables the motor control system designer to implement a robust electrical drive management solution see Fig.

In particular, the availability of absolute position data enables the motor to start up smoothly from any position.

The reduction in torque attributable to inaccurate position data is demonstrated in Fig. Unfortunately, the simplest and cheapest position-sensing systems available to BLDC motor designers to date have not enabled accurate absolute positioning. This means that a back-EMF system has no positional data for a static motor unless it has previously been hard-driven to an alignment point — an operation that will result in forward or backward movement of the motor to such an alignment point, independently of the user.

And after stalling or jamming, this process must be repeated to enable an orderly re-start. Errors in placement produce loss of efficiency or power, so extremely precise assembly is required for a discrete Hall sensor system to work effectively. Each Hall sensor also requires its own signal wires, further complicating the production process. The resulting position measurement error can be significant when angle-related torque loss is considered.

The most damaging drawback of this component type is its potential vulnerability to dust, dirt, and other contaminants. But the high cost of a typical resolver solution, which includes the resolver unit itself plus additional analog and digital support circuitry, is prohibitive in most consumer applications and even in motor drive systems for end products in the industrial and other market segments.

Each of these position sensor options, then, are undermined by one or more of these characteristics:. But what if multiple Hall sensors were integrated in a single chip? This is the approach taken in a family of devices known as absolute magnetic position sensors.

By fabricating multiple, highly sensitive Hall elements on a die — alongside analog, signal processing, and digital circuitry — a position sensor system can be implemented in a single chip paired with a simple magnet.

A single-chip alternative to a discrete Hall sensor solution benefits from the following characteristics:. An example of such a single-chip Hall sensing product is the A from ams, which has pioneered the magnetic position sensor product category. In the AS, ams has included features that make the sensor system easy to design in and manufacture:.

This simple solution can provide absolute position-sensing data from start-up to a high maximum speed of 28, rpm.


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