Transistor experiments

Software protocol

Objective: To illustrate how computers communicate large amounts of information over a single wire or communication channel

Terms to know:

Protocol: A set of rules that are used to accomplish a task more quickly, more efficiently and more reliably.

Handshaking: An indication that the current task has been completed.  An example would be acknowledging the receipt of a piece of e-mail by sending back a reply.

Encoding: Putting the information in a format that can be easily understood by the program or person receiving it.  Examples include: Web browser instructions in web pages (HTML), printer instructions when you send a document to your printer (Postscript), protection of your credit card number when you order something on the web (encryption)

Half Duplex: This is when you can only send or receive information at one time using communication medium (example - telephone conversation)

Full Duplex: Being able to send and receive information simultaneously (example - web surfing while downloading a game)

Packet: A group of information to be sent or received  (example: when you download a new program, it comes in pieces called packets.  This way the sending computer can try to resend just that piece of information if needed, not the entire program)

Address: A way of identifying each user.  In the Internet this is the same as a web address like www.netscape.com or www.ibm.com

Arbiter: This is usually a software program that decides who gets to go first when multiple requests come for accessing the same information.  On the Internet, this is what tells you that it failed to connect, try again later when many people are visiting the same site like mp3.com.

Node: This is a connection on the network.  When you connect to the Internet, your computer becomes a node or connection on the World Wide Web. Each node has an address as well so that your computer can be identified from all other ones.

Error detection/correction - these is what happens when you make a request for information or send an e-mail and it does not work.  Example would be the e-mail system may tell you that it failed to deliver your e-mail.  A download you try may also fail and have to restart.

Broadcast message:  This is when one person talks and all others on the network are supposed to listen.  An example of this would be an emergency warning for a tornado on the radio.

One to One message :  This is where you establish a conversation with another person or computer much like a telephone conversation

Materials required:

For each group of 5 students you need:

½ of a wardrobe box (mover's supply) cut in height

 4 sections of 1" PVC pipe cut in 2' lengths

4 sections of 1" PVC pipe cut in 6" lengths

1 4-way tee in 1" PVC

4 1" standard tees

4 1" 90 degree elbows

The illustration shows the setup where this is a cross section of the wardrobe box with pipes passing through it.  One student is positioned at each of the four sides.

The purpose of the box is to obstruct your view of the partner opposite.  The pipe is the communication medium.  You are each given a short section of pipe and two pipe connectors to form a headset like a  phone so you can talk and listen.

As a group you need to select one student to be the arbiter.  This person will roam around the box and  decide who goes next. Conceptually, the arbiter in the network is shown at the center but due to safety concerns we made this person roam.  This network will be used to perform two types of message passing, broadcast and one to one.

Process Steps:

1) One person in the group is selected as an arbiter.

2) The other four students spread out and stand next to a node.  You are given a short piece of pipe, a t-junction and an elbow to construct a headset

3) You will be given index cards with messages to convey to your team.   At the top of each card will be written either Broadcast or the node name you need to send the information to.  In a broadcast you need  to send it to all other nodes.

4) Each time you need to speak, you need to ask permission of the arbiter.  This person will need to  decide when you can go.  You ask permission by stating your node name and then the intended audience.  Like green broadcast or green to red.  You need to wait for the arbiter to grant permission before you can go.

5) Each message will be a few sentences but you can only send 5 letters at a time before someone else takes a turn.  You need to include spaces or punctuation in the letter count.  For example, you may be asked to communicate:

"The sky looks like a storm is coming"

The first time you could pass The spaces then another person get a turn.

The 5 characters you send would be called a packet.

To indicate you are done with a message a special character called "done" should be sent.

6) The goal is to communicate all information on each of your cards first as a team.  Points will be awarded as follows:

First to be done: 10 points

Second finished:   9 points

Third                    8 points

Fourth                  7 points

Fifth                      6 points

Sixth                     5 points

Message accuracy

Perfect message on the card send: 10 points each error deducts 1 point

Discussion questions

1) What worked best to help this process?

2) How could you improve accuracy or speed?

3) Which seems to help you get the most points?

Did you ever wonder how any of the following things happen?

1) You click on a web page link and see another page come to your screen

 2) You pick up the telephone, dial a number and are connected to the person you want

3) You ask to print something from your computer and somehow it prints on your paper 

4) You type on your keyboard and it shows up on your computer screen

5) You have a cable modem hooked to your computer and the computer is not confused by seeing all the tv information that is on the same cable

 All of these are examples of software protocols in use.  A protocol is really nothing more than a set of rules used to communicate information. 

NOTE - (Courtesey of Michael Riley and his team)These were just ideas that worked for us.  We were working with small-ish classes (~25 students) of 11th and 12th graders. Your experiences may vary. These are just ideas that occurred to us as we taught…

This note is divided as follows:
1. Rough Agenda
2.  Intro Topics (i.e. - making "software protocol" relevant)
3.  Extension Topics (i.e. - challenge exercises after the main lab)
4.  Tricks we learned

Rough Agenda

If you have 90 minutes (we did):

• Introductions, outline agenda, set expectations - 10 minutes
• Intro topics (see below) - 10 minutes
• Lab instructions (distribute materials, help people with setup) - 5 minutes
• Run the lab - 20 minutes
• Stop the lab, task each team with getting ready to talk about "what worked/what didn't", tabulate and post results - 10 minutes
• Talk about (and possibly run) extensions to the experiment:  mentioned below - 20 minutes
• Close

Mouse trap vehicle

Materials under stress

Experiment 1: Materials Deform Under Stress

In this  exercise, we will explore the behavior of elastic bodies under load, identifying parts that are under stress (compression or tension). In the following steps, observe the space between the grid lines on the flexible (elastic) urethane foam beam. Refer to figure 1 as you perform the following experiments.

Step 1:

Place the foam beam on a flat surface such that it at rest. Measure the horizontal distance between the lines ________________ When an elastic material is at rest, is there any stress in the material?

If you apply force to an elastic material (press down on it), what happens?

When the force is removed, what happens?

Name some elastic materials.

Step 2:

Have two of your team push on the ends of the beam. Measure the horizontal distance between the lines. ___________

What happens to the material?

Step 3:

Have two of your team pull on the ends of the beam. Measure the distance between the lines. ______ What happens to the material?

 Step 4:

Have one of your team bend the beam. What happens to the material near the top edge?

The top edge of the beam is under which type of stress?

What happens to the material at the bottom edge of the beam ?

The top edge of the beam is under which type of stress ?

What happens to the material in the middle of the beam ?

Is the material in the middle of the beam under any stress ?

Experiment #2: Strength of Beams

In this experiment you will be loading a beam with weight to determine its breaking strength and discovering the tensile and compressive  properties of the material, the effects of the shape of the beam on load capacity, and the concept of reinforcement. In each step lay the specified beam across the supports with the weight box suspended in  the middle of the beam. When adding weight, support the box with a pencil to minimize the shock of dropping a weight into the box. Continue adding weigh until the beam fails (listen for the crackle as the beam nears it maximum capacity). In each step, inspect the beam at the point of failure to determine how the beam failed.

Step 1:

Place a beam across the span as shown in Figure 3 such that the wide dimension is horizontal (facing up). Start with ______ weights in the weight box. Gently add weights to the weight box until the beam fails. How much weight did it hold? __________ Did the top of the beam crumple or  did the bottom of the beam tear when it failed?

Did the beam fail in compression or tension?

If the beam were twice as wide, how much weight would it hold? __________

Explain your prediction.

Step 2:

For this step, place the beam across the span with the wide dimension vertical. Predict whether it will hold more or less weight. ________How much weight did the beam hold ?__________ Were the results what you had predicted ?_________ Can you explain the results?

If the beam were twice as thick, how much weight would it hold? _______

Explain your prediction.

Step 3:

For this step, use a beam that has a piece of tape along one of the narrow edges. Should the beam be positioned with the taped edge up or down? ______ Explain why.

Predict whether the beam will hold more or less weight. __________  How much weight did the beam hold?________ Were the results what you had predicted? _________ Explain your prediction and the actual result.

Why does a tiny bit of tape have such a large effect on the load carrying capacity of the beam?

Would adding tape to the top of the beam make it even stronger? _____ Explain.

Can you think of an application of what you have learned here.?

 What is the name of the material used to reinforce concrete?

Experiment #3: Gerdanken Experiment:

Many beams have shapes similar to those shown in Figure 3

What Is the name for beams shaped like the capital letter I?

Why are beams shaped like this?

Can you name at least three benefits of building  beams in these shapes?

Can you name some of the places where each type of beam is used.?

Summary of Experiments

 Key words: Compression, Tension, Stress and Lever Arm

 How do are the principles of levers applied to increase the load a beam can carry?

Is relative strength of materials under compression and under tension always the same?

Why is this important?

What techniques can be used to balance the strength of structure members?

Why are beams (e.g., a crane booms) fabricated out of many cross members or with cut-outs rather than being solid?

Why does adding a small amount of tensile material improves the strength balance of concrete beams?

Build a raft

For those interested in more, most Amateur Radio clubs in the area  give classes which cover the electronic basics and Morse code that is necessary to obtain  a Ham radio license. If there are enough that sign up at a school, the clubs will go to  the school to give the class. Costs for their own radio station is fairly inexpensive and  this has been a great way to get people involved and interested in electronics. Some of  these  kids then grow up to become great electronic engineering designers.