Operation of a Doorbell Buzzer

Introduction: (Initial Observation)

When Thomas Edison worked as a boy on the Grand Trunk Railroad in Michigan, he became familiar with the telegraph system that linked the eastern part of the U.S. with the western part. And recognizing the vital importance of this cross-country communications system. He later made many improvements to it. Buzzer is very similar to the telegraph sounder, only instead of producing a single click when the code key is depressed as did the telegraph, the buzzer gives off a continuous sound.

He later invented electric pencil with the same method that you are about to build a buzzer today.

A doorbell buzzer is one of the oldest electrical products that has been used in every home and business since it’s invention. The same design is manufactured in different sizes and has been used as Fire alarm, school bell, telephone ring, service bell and many more. In this project we will design and build a simple buzzer.

Information Gathering:

Find out about s doorbell buzzer. Read books, magazines or ask professionals who might know in order to learn about the design and construction of a buzzer. Keep track of where you got your information from.

Buzzer is just an electromagnet which breaks the circuit which is activating it when it is activated, you can make your own buzzer by winding about 100-200 turns of wire around a nail and arranging it so that activating this electromagnet pulls on an armature which opens a set of contacts and breaks the circuit to the electromagnet. As soon as the circuit is broken, a spring returns the armature to it’s original position and the circuit is made again. This cycle of break-the-circuit and make-the-circuit continues and makes the armature vibrate or buzz for as long as a voltage is applied.

Take a close look at the pictorial diagram of a buzzer. It is so easy to make one of these on a piece of board. The electromagnet is just a soft iron bolt (any bolt would do) about 75mm long. I wind as many turns of single strand telephone wire. The armature is just a strip of tin about 5mm wide and 75 mm long. A nail holds it on the board.
The red arrow shows where the current will flow when the battery is connected. The armature forms part of the circuit for current flow. However after the battery has been connected for a fraction of seconds the magnetic field builds up around the electromagnet and the electromagnet pulls the armature towards it. When the armature moves toward the electromagnet the circuit current is broken. The magnetic field about the electromagnet collapse and the armature springs back to the contact. Current can now flow again and the whole cycle is repeated over and over. The result is that the motion of the armature heating the electromagnet makes a buzzing sound.

Who is the inventor of buzzer?

Joseph Henry made the first electric bell or buzzer. Manufacturers have later made additional changes and improvements, but the general concept has remained unchanged.

Use this link for more details:

http://www.mainlesson.com/display.php?author=bachman&book=inventors&story=electric

Question/ Purpose:

The purpose of this project is to build a simple buzzer and find out how a direct electric current can cause a vibrating motion and buzzing sound.

Identify Variables:

Every element used in design of a buzzer is a variable that can affect the final work of the buzzer. The voltage of battery, diameter of electromagnet wire, number of turns of wire on the electromagnet, type and flexibility of material are among those variables. However we will not study the effect of these variables, instead we attempt to find and make any workable combination.

Hypothesis:

My hypothesis is that movements of a buzzer armature will in turn move a switch from on to off position and vice versa. Such a switching action will result continues buzzing sound of the armature (or the sound of a gung and bell attached to it).

Experiment Design:

Building a Buzzer

Step 1

1. Cut off approximately 3 meters of coated copper wire from the wire spool. With a piece of sandpaper, remove the insulating coating from about 1 inch of one end of the wire. Be sure to remove all the insulation so that electrical contact can be made.
2. Let the end of the wire extend several inches beyond the edge of the wood strip that is farther from the nail. With the wire next to the wood, begin wrapping the wire around the nail, distributing the wire evenly along the length of the nail.
3. Wrap the wire until all but 4 inches of the wire have been used. Finish winding with the last turn of wire at the bottom of the nail.
4. Using sandpaper, remove the insulation from about 1 inch of the other end of the wire so that both ends have been stripped of insulation.
5. Which component of your buzzer did you just make?

__the wire wrapped around the nail is an electromagnet__

Step 2 (A way to make the steady DC current into a changing current)

1. Bend the paper clip so that it looks like the buzzer model on your table.
2. Position the base of the paper clip on the board. Staple the base of the paper clip to the board so that the staple straddles the two smaller parts of the paper clip. You may need more than one staple.
3. Bend the nonmagnetic wire to look like the model. Position the wire on the board so that the loop is over the top of the nail. Make sure that the top end of the clip extends just slightly above the end of the paper clip.
4. Staple the wire to the board.

Step 3

1. Take one end of the copper wire wrapped around the nail and wrap it several times around the base of the nonmagnetic wire. Make sure the cleaned portion of the copper wire is in contact with the nonmagnetic wire. After wrapping the wire, you may want to secure it to the board with a staple.
2. Attach one clip lead from a 6-volt battery or DC power source to the far end of the paper clip and the other clip lead to the free end of the coil of wire wrapped around the nail.
3. If adjusted properly, the buzzer should begin to buzz when the clip leads are connected. (You may need to adjust the position of the nonmagnetic wire relative to the nail head and the paper clip.)

Important: In the above diagram, the red wire is a magnetic wire such as steel or Iron paperclip. The black wire is a non-magnetic wire such as copper or aluminum.

In this model, green wire from the battery is connected to the electromagnet wire. The electromagnet wire turns about 200 turns around the bolt and then connects to the copper strip. Copper strip is secured on the board with two screws. It is then bended over the steel strip and touching it. Steel strip is also secured on the board and connected to the other pole of the battery using the red wire. The distance between the head of the bolt and the steel strip is about 3 to 4 millimeters.

This is another electric bell model made using the parts available in the Advanced Electromagnetism kit of MiniScience.com. The online instructions used for this kit are available Here.

Materials and Equipment:

List of material can be extracted from the experiment design. This is a partial list:

1. A DC power source that provides a steady, unchanging current. A 6 volts lantern battery works good for this experiment.
2. Paper Clips (as magnetic wire)
3. Copper or aluminum wire (as non-magnetic wire)
4. Insulated magnet wire. (This actually is copper wire coated with a resin. Since it is being used to make electromagnets, it is known as magnet wire. Magnet wire is used in construction of electric motors, transformers and electromagnets. The resin used to coat magnet wire is often clear, so you may mistake magnet wire with bare copper wire. Wire gage of 24 or more must be used for this experiment, but remember higher gage means less thickness). Magnet wire 28 AWG is available at MiniScience.com. The electromagnet kit of MiniScience also include the magnet wire as well as metal pieces.
5. Connecting wires (Any insulated wire)

Results of Experiment (Observation):

How does the buzzer work?

1) What type of circuit results when the paper clip and wire are not in contact?

An open circuit results due to the break in the conducting pathway.

2) Why is it necessary for the paper clip and the nonmagnetic wire to break contact?

This turns the current on and off, creating a changing current which induces a changing magnetic field.

3) What causes a changing current in the buzzer?

Current from the power supply flows through the wire wrapped around the nail and creates an electromagnet. The electromagnet’s magnetic field attracts the paperclip down toward the nail head. As the clip moves toward the nail, it loses contact with the nonmagnetic wire to the left of the nail. When the paperclip and the wire are no longer touching, the circuit is broken and current stops flowing.

4) What causes the paper clip to move up and down?

The paperclip makes a buzzing sound as vibrates up and down. When the circuit is broken and no current is flowing, the wire around the nail has no magnetic field and does not attract the paper clip. The paper clip springs back up until it touches the nonmagnetic wire again. Now the circuit is complete and current flows through the wire wrapped around the nail, making it into an electromagnet. The electromagnet pulls the paper clip down toward the nail and away from the nonmagnetic wire, breaking the circuit. This process repeats.

Calculations:

Not required.

Summery of Results:

Summarize what happened. This can be in the form of a table of processed numerical data, or graphs. It could also be a written statement of what occurred during experiments.

It is from calculations using recorded data that tables and graphs are made. Studying tables and graphs, we can see trends that tell us how different variables cause our observations. Based on these trends, we can draw conclusions about the system under study. These conclusions help us confirm or deny our original hypothesis. Often, mathematical equations can be made from graphs. These equations allow us to predict how a change will affect the system without the need to do additional experiments. Advanced levels of experimental science rely heavily on graphical and mathematical analysis of data. At this level, science becomes even more interesting and powerful.

Conclusion:

Using the trends in your experimental data and your experimental observations, try to answer your original questions. Is your hypothesis correct? Now is the time to pull together what happened, and assess the experiments you did.

Related Questions & Answers:

What you have learned may allow you to answer other questions. Many questions are related. Several new questions may have occurred to you while doing experiments. You may now be able to understand or verify things that you discovered when gathering information for the project. Questions lead to more questions, which lead to additional hypothesis that need to be tested. Following are some possible questions.
How could you cause the buzzer to make a different noise?
What do you think would happen if more batteries were added?
Would there be a difference if more turns of wire were added?

Possible Errors:

If your buzzer does not work, check the following possible problems.

1. Dead batteries; replace them
2. Batteries working against each other. (Be sure batteries are connected positive end to negative end
3. Not enough batteries. (Try more batteries, but never more than twelve D batteries, or eighteen volts total.)
4. Loose wires.
5. Not enough wire wound on the nail to make a strong electromagnet.
6. Parts too loosely joined.
7. Poor adjustment of metal pieces.
8. Extra wires where they are not needed, or wires touching each other, or metal where there should not be.
9. Wires not touching other wires or pieces of metal they should be touching. (Wire connections must have the enamel sanded off or the insulation removed.)
10. Try moving the position of the battery supporting the metal strip or pushing the nail farther into the board or pulling it out.

References:

Visit your local library and review the books related to electricity, magnetism and physics. Look for any material related to an electric bell. List such books in the reference section of your project guide.

Following are some related online pages/ articles:

http://uv201.com/Misc_Pages/bell.htm

http://www.bellsystemmemorial.com/telephones-technical-ringers.html

http://www.nelsonthornes.com/secondary/science/scinet/scinet/electric/magnets/bell.htm