How to Make a Simple Electric Motor

Energy comes in many forms. Electric energy can be converted into useful work, or mechanical energy, by machines called electric motors. Electric motors work due to electromagnetic interactions: the interaction of current (the flow of electrons) and a magnetic field.

Problem

Find out how to make a simple electric motor.

Materials

• D battery
• Insulated 22G wire
• 2 large-eyed, long, metal sewing needles (the eyes must be large enough to fit the wire through)
• Modeling clay
• Electrical tape
• Hobby knife
• Small circular magnet
• Thin marker

Procedure

1. Starting in the center of the wire, wrap the wire tightly and neatly around the marker 30 times.
2. Slide the coil you made off of the marker.
3. Wrap each loose end of the wire around the coil a few times to hold it together, then point the wires away from the loop, as shown:

What is this? What is its purpose?

4. Ask an adult to use the hobby knife to help you remove the top-half of the wire insulation on each free end of the coil. The exposed wire should be facing the same direction on both sides. Why do you think half of the wire needs to remain insulated?

5. Thread each loose end of the wire coil through the large eye of a needle. Try to keep the coil as straight as possible without bending the wire ends.

6. Lay the D battery sideways on a flat surface.
7. Stick some modeling clay on either side of the battery so it does not roll away.
8. Take 2 small balls of modeling clay and cover the sharp ends of the needle.
9. Place the needles upright next to the terminals of each battery so that the side of each needle touches one terminal of the battery.

10. Use electrical tape to secure the needles to the ends of the battery. Your coil should be hanging above the battery.
11. Tape the small magnet to the side of the battery so that it is centered underneath the coil.

12. Give your coil a spin. What happens? What happens when you spin the coil in the other direction? What would happen with a bigger magnet? A bigger battery? Thicker wire?

Results

The motor will continue to spin when pushed in the right direction. The motor will not spin when the initial push is in the opposite direction.

Why?

The metal, needles, and wire created a closed loop circuit that can carry current. Current flows from the negative terminal of the battery, through the circuit, and to the positive terminal of the battery. Current in a closed loop also creates its own magnetic field, which you can determine by the “Right Hand Rule.” Making a “thumbs up” sign with your right hand, the thumb points in the direction of the current, and the curve of the fingers show which way the magnetic field is oriented.

In our case, current travels through the coil you created, which is called the armature of the motor. This current induces a magnetic field in the coil, which helps explain why the coil spins.

Magnets have two poles, north and south. North-south interactions stick together, and north-north and south-south interactions repel each other. Because the magnetic field created by the current in the wire is not perpendicular to the magnet taped to the battery, at least some part of the wire’s magnetic field will repel and cause the coil to continue to spin.

So why did we need to remove the insulation from only one side of each wire? We need a way to periodically break the circuit so that it pulses on and off in time with the rotation of the coil. Otherwise, the copper coil’s magnetic field would align with the magnet’s magnetic field and stop moving because both fields would attract each other. The way we set up our engine makes it so that whenever current is moving through the coil (giving it a magnetic field), the coil is in a good position to be repelled by the stationary magnet’s magnetic field. Whenever the coil isn’t being actively repelled (during those split second intervals where the circuit is switched off), momentum carries it around until it’s in the right position to complete the circuit, induce a new magnetic field, and be repelled by the stationary magnet again.

Once moving, the coil can continue to spin until the battery is dead. The reason that the magnet only spins in one direction is because spinning in the wrong direction will not cause the magnetic fields to repel each other, but attract.

Electric motor

       An electric motor is a device used to convert electrical energy to mechanical energy. Electric motors are extremely important in modern-day life. They are used in vacuum cleaners, dishwashers, computer printers, fax machines, video cassette recorders, machine tools, printing presses, automobiles, subway systems, sewage treatment plants, and water pumping stations, to mention only a few applications.

Principle of operation

The basic principle on which motors operate is Ampere's law. This law states that a wire carrying an electric current produces a magnetic field around itself. Imagine that current is flowing through

A figure of an electric motor. 

the wire loop shown in the figure below. The presence of that current creates a magnetic field around the wire. Since the loop itself has become a magnet, one side of it will be attracted to the north (N) pole of the surrounding magnet and the other side will be attracted to the south (S) pole of the magnet. The loop will begin to rotate, as shown by the arrow marked F.

AC motors. 

What happens next depends on the kind of electric current used to run the motor, direct (DC) or alternating (AC) current. With AC current, the direction in which the current flows changes back and forth rapidly and at a regular rate. In the United States, the rate of change is 60 times per second, or 60 hertz (the unit of frequency).

In an AC motor, then, the current flows first in one direction through the wire loop and then reverses itself about 1/60 second later. This change of direction means that the magnetic field produced around the loop also changes once every 1/60 second. At one instant, one part of the loop is attracted by the north pole of the magnet, and at the next instant, it is attracted by the south pole of the magnet.

But this shifting of the magnetic field is necessary to keep the motor operating. When the current is flowing in one direction, the right hand side of the coil might become the south pole of the loop magnet. It would be repelled by the south pole of the outside magnet and attracted by the north pole of the outside magnet. The wire loop would be twisted around until the right side of the loop had completed half a revolution and was next to the north pole of the outside magnet.

If nothing further happened, the loop would come to a stop, since two opposite magnetic poles—one from the outside magnet and one from the wire loop—would be adjacent to (located next to) each other. And unlike magnetic poles attract each other. But something further does happen. The current changes direction, and so does the magnetic field around the wire loop. The side of the loop that was previously attracted to the north pole is now attracted to the south pole, and vice versa. Therefore, the loop receives another "kick," twisting it around on its axis in response to the new forces of magnetic attraction and repulsion.

Thus, as long as the current continues to change direction, the wire loop is forced to spin around on its axis. This spinning motion can be used to operate any one of the electrical appliances mentioned above.

DC motors. 

When electric motors were first invented, AC current had not yet been discovered. So the earliest motors all operated on DC current, such as the current provided by a battery.

Capacitor

A capacitor is a device for storing electrical energy. Capacitors are used in a wide variety of applications today. Engineers use large banks of capacitors, for example, to test the performance of an electrical circuit when struck by a bolt of lighting. The energy released by these large capacitors is similar to the lightning bolt. On another scale, a camera flash works by storing energy in a capacitor and then releasing it to cause a quick bright flash of light. On the smallest scale, capacitors are used in computer systems. A charged capacitor represents the number 1 and an uncharged capacitor a 0 in the binary number system used by computers.

How a capacitor stores energy A capacitor consists of two electrical conductors that are not in contact. The conductors are usually separated by a layer of insulating material known as a dielectric. Since air is a dielectric, an additional insulating material may not have to be added to the capacitor.

Think of a capacitor as consisting of two copper plates separated by 1 centimeter of air. Then imagine that electrical charge (that is, electrons) are pumped into one of the plates. That plate becomes negatively charged because of the excess number of electrons it contains. The negative charge on the first copper plate then induces (creates) a positive charge on the second plate.

As electrons are added to the first plate, one might expect a current to flow from that plate to the second plate. But the presence of the dielectric prevents any flow of electrical current. Instead, as more electrons are added to the first plate, it accumulates more and more energy. Adding electrons increases energy because each electron added to the plate has to overcome repulsion from other electrons already there. The tenth electron added has to bring with it more energy to add to the plate than did the fifth electron. And the one-hundredth electron will have to bring with it even more energy. As a result, as long as current flows into the first plate, it stores up more and more electrical energy.

Capacitors release the energy stored within them when the two plates are connected with each other. For example, just closing an electric switch between the two plates releases the energy stored in the first plate. That energy rushes through the circuit, providing a burst of energy.

The primary difference between a DC motor and an AC motor is finding a way to change the direction of current flow. In direct current, electric current always moves in the same direction. That means that the wire loop in the motor will stop turning after the first half revolution. Because the current is always flowing in the same direction, the resulting magnetic field always points in the same direction.

To solve this problem, the wire coming from the DC power source is attached to a metal ring cut in half, as shown in the figure. The ring is called a split-ring commutator. At the first moment the motor is turned on, current flows out of the battery, through the wire, and into one side of the commutator. The current then flows into the wire loop, producing a magnetic field.

Once the loop begins to rotate, however, it carries the commutator with it. After a half turn, the ring reaches the empty space in the two halves and then moves on to the second half of the commutator. At that point, then, current begins to flow into the opposite side of the loop, producing the same effect achieved with AC current. Current flows backward through the loop, the magnetic field is reversed, and the loop continues to rotate.

Mobile phone tracking

Mobile phone tracking refers to the attaining of the current position of a mobile phone, stationary or moving. Localization may occur either via multilateration of radio signals between (several) radio towers of the network and the phone, or simply via GPS. To locate the phone using multilateration of radio signals, it must emit at least the roaming signal to contact the next nearby antenna tower, but the process does not require an active call. GSM is based on the signal strength to nearby antenna masts.

Mobile positioning, which includes location based service that discloses the actual coordinates of a mobile phone bearer, is a technology used by telecommunication companies to approximate the location of a mobile phone, and thereby also its user (bearer). The more properly applied term locating refers to the purpose rather than a positioning process. Such service is offered as an option of the class of location-based services (LBS).

Technology

The technology of locating is based on measuring power levels and antenna patterns and uses the concept that a powered mobile phone always communicates wirelessly with one of the closest base stations, so knowledge of the location of the base station implies the cell phone is nearby.

Advanced systems determine the sector in which the mobile phone resides and roughly estimate also the distance to the base station. Further approximation can be done by interpolating signals between adjacent antenna towers. Qualified services may achieve a precision of down to 50 meters in urban areas where mobile traffic and density of antenna towers (base stations) is sufficiently high. Rural and desolate areas may see miles between base stations and therefore determine locations less precisely.

GSM localization is the use of multilateration to determine the location of GSM mobile phones, or dedicated trackers, usually with the intent to locate the user.

Network-based

Network-based techniques utilize the service provider's network infrastructure to identify the location of the handset. The advantage of network-based techniques (from a mobile operator's point of view) is that they can be implemented non-intrusively, without affecting the handsets.

The accuracy of network-based techniques varies, with cell identification as the least accurate and triangulation as moderately accurate, and newer "Forward Link" timing methods as the most accurate. The accuracy of network-based techniques is both dependent on the concentration of base station cells, with urban environments achieving the highest possible accuracy, and the implementation of the most current timing methods.

One of the key challenges of network-based techniques is the requirement to work closely with the service provider, as it entails the installation of hardware and software within the operator's infrastructure. Often, a legislative framework, such as E911, would need to be in place to compel the cooperation of the service provider as well as to safeguard the privacy of the information.

Handset-based

Handset-based technology requires the installation of client software[5] on the handset to determine its location. This technique determines the location of the handset by putting its location by cell identification, signal strengths of the home and neighboring cells, which is continuously sent to the carrier. In addition, if the handset is also equipped with GPS then significantly more precise location information is then sent from the handset to the carrier.

The key disadvantage of this technique (from mobile operator's point of view) is the necessity of installing software on the handset. It requires the active cooperation of the mobile subscriber as well as software that must be able to handle the different operating systems of the handsets. Typically, smartphones, such as one based on Symbian, Windows Mobile, Windows Phone, BlackBerry OS, iOS, or Android, would be able to run such software. E.g. UonMap application.

One proposed work-around is the installation of embedded hardware or software on the handset by the manufacturers, e.g. E-OTD. This avenue has not made significant headway, due to the difficulty of convincing different manufacturers to cooperate on a common mechanism and to address the cost issue. Another difficulty would be to address the issue of foreign handsets that are roaming in the network.

SIM-based

Using the SIM in GSM and UMTS handsets, it is possible to obtain raw radio measurements from the handset. The measurements that are available can include the serving Cell ID, round trip time and signal strength. The type of information obtained via the SIM can differ from what is available from the handset. For example, it may not be possible to obtain any raw measurements from the handset directly, yet still obtain measurements via the SIM.

WiFi

Crowdsourced Wifi data can also be used to identify a handset's location. Poor performance of the GPS-based methods in indoor environment and increasing popularity of WiFi have encouraged companies to design new and feasible methods to carry out WiFi-based indoor positioning. Most smartphones combine GPS with Wi-Fi positioning systems.

Hybrid

Hybrid positioning systems use a combination of network-based and handset-based technologies for location determination. One example would be some modes of Assisted GPS, which can both use GPS and network information to compute the location. Both types of data are thus used by the telephone to make the location more accurate (i.e. A-GPS). Alternatively tracking with both systems can also occur by having the phone attain its GPS-location directly from the satellites, and then having the information sent via the network to the person that is trying to locate the telephone. Services allowing such cellphone include Google Latitude. Other examples would be LTE's OTDOA and E-CellID.

There are also hybrid positioning systems which combine several different location approaches to position mobile devices by WiFi, WiMAX, GSM, LTE, IP addresses, and network environment data.

Operational purpose

In order to route calls to a phone, the cell towers listen for a signal sent from the phone and negotiate which tower is best able to communicate with the phone. As the phone changes location, the antenna towers monitor the signal, and the phone is roamed to an adjacent tower as appropriate.

By comparing the relative signal strength from multiple antenna towers, a general location of a phone can be roughly determined. Other means make use of the antenna pattern, which supports angular determination and phase discrimination.

Newer phones may also allow the tracking of the phone even when turned on and not active in a telephone call. This results from the roaming procedures that perform hand-over of the phone from one base station to another.

Bearer interest

A phone's location can be uploaded to a common website where one's friends and family can view one's last reported position. Newer phones may have built-in GPS receivers which could be used in a similar fashion, but with much higher accuracy.

This may be controversial, because having this data on a common website may mean that people who are not 'friends and family' may be able to view the info, most obviously, the owners of the site.

Privacy

Locating or positioning touches upon delicate privacy issues, since it enables someone to check where a person is without the person's consent. Strict ethics and security measures are strongly recommended for services that employ positioning, and the user must give an informed, explicit consent to a service provider before the service provider can compute positioning data from the user's mobile phone.

In Europe, where most countries have a constitutional guarantee on the secrecy of correspondence, location data obtained from mobile phone networks is usually given the same protection as the communication itself. The United States, however, has no explicit constitutional guarantee on the privacy of telecommunications, so use of location data is limited by law.

Officially, the authorities (like the police) can obtain permission to position phones in emergency cases where people (including criminals) are missing. The U.S. Justice Department has argued that current laws allow them to track suspects without having probable cause to suspect a law is being violated. In some instances, law enforcement may even access a mobile phone's internal microphone to eavesdrop on local conversations while the phone is switched off.

The Electronic Frontier Foundation is tracking some cases, including USA v. Pen Register, regarding government tracking of individuals.

In the US, an interpretation of The Patriot Act that is secret, but confirmed to exist, has been linked to secret widespread location tracking.

China has proposed using this technology to track commuting patterns of Beijing city residents.Aggregate presence of mobile phone users could be tracked in a privacy-preserving fashion.

Cell Phone Detection

Had a cell phone detector been around, it would have picked up the world’s first ever cell phone call being placed in the dark ages of the twentieth century, a few months after the end of the Apollo moon program, before most people had heard of the Internet, and long before the invention of the World Wide Web. The date was April 3, 1973, and the device was a Motorola “brick” weighing more than four-and-one-half pounds and measuring some nine inches by five inches by one-and-three-quarter inches.

The dimensions of cell phones have shrunk dramatically in the intervening years, while their capabilities have grown exponentially, as has cell phone ownership. Their sophistication and ubiquity pose many security challenges, and have given rise to a demand for equally sophisticated cellular phone detection.

Cell phone detector applications

In addition to being able to make old-fashioned phone calls, today’s phones allow text messaging, photography, and recording and real-time transmission of audio and video. In short, they provide a wide variety of ways of recording and communicating information. In addition, the tiny size of modern phones makes them fiendishly difficult to detect if you are trying to prevent their introduction and use in a particular location. In many cases, it is simply not acceptable to pat down visitors and guests to make sure they are not secreting a phone on their person.

And there are plenty of times and places you might not want a cell phone to be used. They are a perfect tool for espionage, whether in military or government installations, or for industrial espionage. Security personnel at all such locations frequently deploy cell phone detection measures to assure the security of their information. In other circumstances, they can make possible various kinds of illegal activities, such as in prisons and other correctional institutions: a cell phone detector for prisons is a common application, for example. A mobile phone detector, or a network of them, can also be used to monitor for inappropriate transmissions in a casino, or to ensure that workers in a hazardous area are not using a cell phone that may distract them and cause an accident. These are just a few of the situations in which it is invaluable to deploy a mobile cell phone detector.

Latest Main Projects List For EE | Electrical Engineering - 2013

1. Zigbee based obstacle sensing robot
2. Zero sequence blocking transformer using three single phase transformers
3. Vector control of 3 phase induction motor using double level vsi.
4. Under ground cable fault detector
5. Three phase fault detection
6. Speed control of dc motor using radio frequency
7. Speed control of dc motor using dc chopper
8. Speed control of brushless dc motor
9. Speed control and power factor improvement in induction motor
10. Software for pnuematic system for hal - hybrid assistive limb
11. Smart metering in smart grid
12. Single phase inverter fed from fixed dc source
13. Single phase five level inverter
14. Simulation of upfc control
15. Sign language translator
16. Robotic arm with 4 degrees of freedom
17. Multi-input dc boost converter for grid connected hybrid pv/fc/battery power system
18. Modelling and control of rotary inverted pendulum
19. Microcontroller based dc motor control
20. Making a teaching kit using raspberry pi
21. Low cost implementation of digital relays
22. Load voltage regulation using vrs
23. Micro grid power management
24. Implementation of wavelet based ac motor fault detection using arm processor
25. Harmonic filter
26. Development of software package for sequential and synchronous operations of six motor drives.
27. Development of advanced embedded system for home security using gsm
28. Design a standby power supply across 220v mains
29. Dc motor speed control using pic microcontroller
30. Character and face recognition
31. Brake fault detection for four wheeler
32. Automatic control of hybrid bicycle
33. Advanced ir remote control switch board
34. Wireless energy meter