Video A simple DC Motor and Homopolar Motor

A simple DC Motor DIY
a simple DC motor made from a few wires, couple of magnets and a battery



The simplest motor of the world

A motor made only by a wire and a magnet. It uses one AAA battery.


World's Simplest Motor - Homopolar Spiral
The homopolar spiral motor is one of the simplest and most easy to make motors in the world.




Homopolar Motor - 5 minutes ready to work

How DC electric motor works Video

How DC motor works Video



Direct Current Electric Motor Video



Video DC electric motor explained by Mr. Burshkin
Mr. Burshkin explains how the standard DC motor works

D.C. motors - TORQUE/SPEED CURVES

TORQUE/SPEED CURVES
In order to effectively design with D.C. motors, it is necessary to understand their characteristic curves. For every motor, there is a specific Torque/Speed curve and Power curve.




The graph above shows a torque/speed curve of a typical D.C. motor. Note that torque is inversely proportioal to the speed of the output shaft. In other words, there is a tradeoff between how much torque a motor delivers, and how fast the output shaft spins. Motor characteristics are frequently given as two points on this graph:

• The stall torque,, represents the point on the graph at which the torque is a maximum, but the shaft is not rotating.
• The no load speed,, is the maximum output speed of the motor (when no torque is applied to the output shaft).

The curve is then approximated by connecting these two points with a line, whose equation can be written in terms of torque or angular velocity as equations 3) and 4):

The linear model of a D.C. motor torque/speed curve is a very good approximation. The torque/speed curves shown below are actual curves for the green maxon motor (pictured at right) used by students in 2.007. One is a plot of empirical data, and the other was plotted mechanically using a device developed at MIT. Note that the characteristic torque/speed curve for this motor is quite linear. This is generally true as long as the curve represents the direct output of the motor, or a simple gear reduced output. If the specifications are given as two points, it is safe to assume a linear curve.

Recall that earlier we defined power as the product of torque and angular velocity. This corresponds to the area of a rectangle under the torque/speed curve with one cornerat the origin and another corner at a point on the curve (see figures below). Due to the linear inverse relationship between torque and speed, the maximum power occurs at the point where = ½ , and = ½ .

http://lancet.mit.edu/motors/motors3.html

HOW TO PLOT SPEED/TORQUE AND CURRENT/TORQUE CURVES
On every bulletin sheet there is sufficient data for you to plot the speed/torque and current/torque curves for each armature available in that particular motor size. Even though ratings are provided for each motor, seldom will you ever operate at that point. You really must draw at least a speed/torque curve to tell the speed at which the motor is going to run. Then, plotting the current/torque curve on the same graph will tell you the amperes required at your particular load point.

ILLUSTRATION 1 SPEED/TORQUE AND CURRENT/TORQUE CURVES 150A100-10 (DMR) @ 27 VDC

http://www.motortech.com/BULL_E-1.htm

Dc Motor Speed Control Lecture Video

DC MOTOR DRIVE FUNDAMENTALS
UNDERSTANDING DC MOTOR DRIVES
DC motors have been available for nearly 100 years. In fact the first electric motors were designed and built for operation from direct current power.
AC motors are Now and will of course remain the basic prime movers for the fixed speed requirements of industry. Their basic simplicity, dependability and ruggedness make AC motors the natural choice for the vast majority of industrial drive applications.

Then where do DC drives fit into the industrial drive picture of the future?
In order to supply the answer, it is necessary to examine some of the basic characteristics obtainable from DC motors and their associated solid state controls. more

Precision DC motor speed controller
Optical tachometers that produce a frequency proportional to RPM are popular feedback sources for precision analog motor speed control. This usually involves a frequency-to-voltage converter (FVC) to convert the tachometer output to a voltage that’s then input to a conventional servo. Though it typically works fine, it’s unnecessarily complicated and requires a tachometer with a relatively high pulse/revolution characteristic to allow for both a reasonably fast loop response and adequate ripple filtering in the FVC. more


DC Motor Speed Control PWM



The user may feel that the RC PWM signal may be an awesome resource to control the speed of a DC motor. And this is of course true, except that the RC PWM signal itself is pretty much useless as a direct means of controlling the DC motor speed. What needs to be done is to have an intermediate circuit to decode the position information (RC Pulse width) and generate a speed magnitude signal. In other words, if the input pulse is 1 ms, move the DC motor on reverse at maximum speed, if 1.5 ms wide stop the DC motor and if 2.0 ms, move the DC motor forward at maximum speed. Any other pulse width is then decoded to partial speed on the corresponding direction. more


Dc Motor Speed Control - Introduction Lecture Video



Dc Motor Speed Control - Block Diagram Lecture Video



Dc Motor Speed Control Current Control & S C L Lecture Video




Dc-Motor Speed Control Controller Design-1 Lecture Video



Dc Motor Speed Control Controller Design-2 Lecture Video

Dc Motor Lecture Video

Basic DC Motor theory
The DC motor has two basic parts: the rotating part that is called the armature and the stationary part that includes coils of wire called the field coils. The stationary part is also called the stator. The armature is made of coils of wire wrapped around the core, and the core has an extended shaft that rotates on bearings. You should also notice that the ends of each coil of wire on the armature are terminated at one end of the armature. The termination points are called the commutator, and this is where the brushes make electrical contact to bring electrical current from the stationary part to the rotating part of the machine.

The coils that are mounted inside the stator are called field coils and they may be connected in series or parallel with each other to create changes of torque in the motor. You will find the size of wire in these coils and the number of turns of wire in the coil will depend on the effect that is trying to be achieved.
more


Basic DC Motors
Principles of operation
In any electric motor, operation is based on simple electromagnetism. A current-carrying conductor generates a magnetic field; when this is then placed in an external magnetic field, it will experience a force proportional to the current in the conductor, and to the strength of the external magnetic field. As you are well aware of from playing with magnets as a kid, opposite (North and South) polarities attract, while like polarities (North and North, South and South) repel. The internal configuration of a DC motor is designed to harness the magnetic interaction between a current-carrying conductor and an external magnetic field to generate rotational motion.



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D C Motors Lecture Video


DC Motor 2 Lecture Video


DC Motor 3 Lecture Video

The Workings of a DC Motor and Interactive Animation

The Workings of a DC Motor
By David Urmann

Electric motors are all around us. In our homes alone, nearly all mechanical and electrical movement you see around is brought about by a DC (direct current) electric motor and AC (alternating current) electric motor.

It was in 1873 that Zénobe Gramme created the contemporary DC electric motor. Gramme linked his devised dynamo to another apparatus and steered it like a motor. His invention, the Gramme device, was the first electric motor that pulled off in the field.

Two good examples of electric DC inventions are the innovative ball-bearing motor and the unusual homo polar motor that Michael Faraday created.

In general, a simple DC electric motor consists of six basic parts. These are the rotor or armature, brushes, axle, commutator, field magnet, and DC power supply. An electric motor is powered by magnets that employ magnet fields to produce torque, setting the motor in motion. Those who previously played with magnets are familiar with the elementary principle of magnets, that similar poles repel and opposites attract. The repelling and attracting electromagnetic forces inside an electric motor make the DC motor to create rotating motion.

Magnets are polarized, with a negative and a positive section. Even with comparatively puny magnets, the repulsion of like poles and the attraction of opposite poles are evident. Direct current electric motor utilizes these components to virtually transform electrical current into shifting movement.

A DC electric motor needs at least one electromagnet. An electromagnet serves as the source of an electric motor and it changes the electricity flow as the motor moves, altering its polarization in order to maintain the operation of the motor. The other magnetic fields are either electromagnets or permanent magnets. The electromagnet is typically to be found in the motor's hub and rotates in the permanent magnets.

A DC electric motor features coils of wire that go around in a magnetic field. The coil is placed in a fixed magnet. The electric flow in the coil is delivered by means of two brushes that produce moving connections with a split ring. The forces applied on the coils of wire initiate for a movement or torque on the coil. The coil also acts as a tiny magnetic dipole.

To better understand and imagine a simple DC electric motor, picture a wheel split into two between two magnets. In this case, the DC motor's wheel is the electromagnet. The two permanent outer magnets are the negative and the positive. Now, suppose that the right magnet is positive and the left magnet is negative.

The coils of wire on the wheel of the DC motor are being brought in with electric flow and this current ignites a magnetic drive. In order to cause the DC motor to twist and more, the wheels on the permanent positive magnet have to be positively charged and the negative permanent magnet have to be negatively charged as well. And, since opposite charges attract and similar charges repel, the wheel shifts in order for its negative piece turns over around to the right and the positive section of the wheel moves to the left. The magnetic force enables the wheel to spin thus, the movement is utilized to perform and operate.

The consistency and straightforward pattern of DC motors make it an ideal option for countless various purposes. DC motors are largely employed for multiple applications such as remote control cars and electric razors.

For more information on DC Electric Motors and Online Electric Motor Repair Advice please visit our website.

Article Source: _http://EzineArticles.com/?expert=David_Urmann

DC Motors Principles of operation and interactive animation
In any electric motor, operation is based on simple electromagnetism. A current-carrying conductor generates a magnetic field; when this is then placed in an external magnetic field, it will experience a force proportional to the current in the conductor, and to the strength of the external magnetic field. As you are well aware of from playing with magnets as a kid, opposite (North and South) polarities attract, while like polarities (North and North, South and South) repel. The internal configuration of a DC motor is designed to harness the magnetic interaction between a current-carrying conductor and an external magnetic field to generate rotational motion.
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The Difference Between AC and DC Electric Motors

The Difference Between AC and DC Electric Motors
By John Francis

There are two main types of electric motors. There are direct current or DC and alternating current or AC motors. The reference of DC or AC refers to how the electrical current is transferred through and from the motor. Both types of motors have different functions and uses. Dc motors come in two general types. They can have brushes or be brushless. AC motors, as well, come in two different types. They can be two phase or three phase. The differences in DC and AC motors are sometimes subtle, but these differences are what make one types better for a certain use.

Direct current or DC electric motors work for situations where speed needs to be controlled. DC motors have a stable and continuous current. DC motors were the first and earliest motors used. They were found, however, to not be as good at producing power over long lengths. Electric companies found using DC motors to generate electric did not work because the power was lost as the electric was transmitted. Brush DC motors use rings that conduct the current and form the magnetic drive that powers the rotor. Brushless DC motors use a switch to produce the magnetic drive that powers the rotor. Direct current motors are often found in appliances around the home.

Alternating current or AC electric motors are used differently based on what type of AC motor it is. Single phase AC motors are known as general purpose motors. They work well in many different situations. These AC motors work great for systems that are hard to start because they need a lot of power up front. Three phase, also called polyphase, AC motors are usually found in industrial settings. These motors also have high starting power built transmit lower levels of overall power. AC power gets its name from the fact that it alternates in power. The amount of power given off by an AC motor is determined by the amount of power needed to operate the system.

DC and AC electric motors are found everywhere from the home to the car to industrial plants. Motors are important to everyday life. Dc motors were introduced and caused a great revolution in the way many things are done. When AC motors came on the market the way motors were looked at changed because of their amazing starting power potential. DC motors and AC motors are different in many ways, but they still both are usede to power the world. http://electricmotors-hq.com Everything you need to know about electric motors from their history to buying new and used.
Article Source: http://EzineArticles.com/?The-Difference-Between-AC-and-DC-Electric-Motors&id=193767

Basic DC Motor

Content

1 Shunt Motor

A schematic diagram of a shunt field DC motor is shown in
Fig.3.30. The armature circuit and the shunt field circuit are
connected across a DC source of fixed voltage Vt. An external field
rheostat (Rfc) is used in the field circuit to control the speed of the
motor. The motor takes power from the DC source, and therefore
the current It flows into the machine from the positive terminal of
the DC source. As both field circuit and armature circuit are
connected to a DC source of fixed voltage, the connections for
separate and shunt excitation are the same. The behavior of the
field circuit is independent of the armature circuit.

2 Power Flow and Efficiency

3 Condition for Maximum Power

4 Torque

5 Series-wound DC motor

6 Armature Torque of a Motor

7 Shaft Torque

8 Speed of a DC Motor

9 Speed Regulation


More ( pdf )
http://faculty.ksu.edu.sa/eltamaly/Documents/Courses/
EE%20339/DC%20Machines2.pdf