Electricity ~ Power to the People February 25, 2008

Just to review, Ohms law allows us to calculate expected current in a circuit:

Suppose we know: 

V = 12V

R = 100Ω 

I = V/R 

  = 12V / 100Ω

  = 0.12A 

  = 120mA 

Power

Power is the amount of energy dissipated by a component over a given time. Another way of saying this is that power is the rate of energy dissipation.

Units and Variable Name:

Name	Formula Symbol	Unit of Measurement
Voltage	V	V (volts)
Current	I	A (amps)
Resistance	R	Ω (ohms)
Power	P	W(watts)

Power is the product of voltage and current.

Power = Current × Voltage   so   P = I × V

The same holds true if we substitute I with V/R in the right hand triangle.

We get P = (V/R)² x R which equals P = V²/R² x R = V²R/R² = V²/R.

Summarizing, the three formulas for power are:

P = I x V or P = I² x R or P = V²/R

Example:

Take a look at the same circuit we looked at in the previous example. The applied voltage is 12 Volts and the total resistance is 100Ω. 

We know the voltage and we know the resistance. What we want to calculate is the power dissipated in the circuit. The Power formula to use is: P = V²/R.

V = 12V

R = 100Ω 

P = V²/R

  = (12V)² / 100Ω

  = 1.44W

So, the power dissipated by the circuit will be 1.44 Watts.

Ohms Law II

Ohmas Law class notes.

The above notes will help you complete this assignment, which is due Wednesday Feb 27 at the beginning of class.

You may have trouble with the first couple questions which deal with Power, which we will discuss tomorrow.

Electricity Introduction February 22, 2008

We have yet to take a look at how electricity really powers our electronic circuits.  Yes, we know we have to power our signals to go throuogh our IC’s, LED’s, etc.  We will take a look at how electricty does what it does.  We are going to be looking at this through a very foggy lens.  What I mean is, we will not be getting down to fine scientific detail – save that for physics class.

Like a River

In many ways, we can think of electricity and circuits kind of like water flowing through a river.  Only we are talking about electrons flowing as electric current.  In a river, the water flows through a river bed, in a circuit the riverbed is the wire or other conductive material.

Conductivity

Electricity needs a medium (material) to flow through.  Some materials allow electricity to do this easily, others…not so much.  The ability to conduct electricity refers to a materials conductivity.  Some materails have a high conductivity, and we generally call these conductors.  Other materials have low conductivity, and we generally refer to them as insulators.  Remember that it is a range, some conductors work better than others; likewise with insulators.

A really good conductor is silver.  Silver is generally the best conductor of the metals.  Slightly better than copper, and quite a bit better than aluminum.  Silver is a good conductor because it provides little resistance to the electricty passing through.  Silver is a good conductor because it gains or loses an electron very easily, so the flowing electrons can travel along nicely.  Silver, however, is often not used for electrical contacts because it corrodes.  A little bit of corrosion on a tiny connector could be disasterous.

Question:  Why is tap water a conductor and pure distiled water an insulator?

Visit: this brief introduction to Ohm’s Law.

Ohms law is a way to calculate the resistance, voltage, and current in a circuit.

Overview of Computer Components February 21, 2008

Before we go any further, we should look at an overview of our computer components.  That way things will make some more sense when we look at any individual component at a deeper level 

Download this document with descriptions of computer components.

Task:

1. Open the above document, then:

• Review
• Highlight important parts, terms, etc. in yellow
• Highlight confusing or non-understood terms in red

2.  In a similar style, add descriptions of:

• Blu-Ray
• Wireless Router
• USB thumb drive
• PCI-e

Save these all with pictures as a Word 97-2003 document.

3.  Create a Blog post that contains:

• An introduction about the document you have created
• A link to download the full version of the document
• The text-only of the 4 component descriptions you have added

Motherboards February 20, 2008

Complete this note.

Inside the Computer February 19, 2008

Introduction 

Now that we have some fundamental knowledge about the history of computers, we can take a closer look at how the computers we use today work.  Computer components can seem complicated when we look at how they work.  It is important to make sure you understand the fundamentals as we move along.  Don’t forget to ask a question the moment something is unclear.  Either post a comment, or ask in class.

First Things First

I would like each ICE 3M student to send me an email to let me know their GMail address, and the URL of their blog.  Example:

From: firstname.lastname@gmail.com 

To: yanthoj2.deletethis@hcdsb.andthis.org

Subject: ICE3M  

Message:

Mr. Yantho,

This is firstname lastname, the address to my Blog is www.besticeblogever.wordpress.com.   

Regards,

Firstname Lastname  

PS You are the best teacher I have ever had.  I mean that in a serious way, not just to suck-up, because I know you hate suck-ups.  Also, good luck this year as you coach the senior girls soccer team to their third straight Halton Championship.

The Basic Computer

Conceptually, a computer is this:

But we usually think of this:

Homework: 

1. Comment on your blog the difference between the two “ideas” of a computer.
2. Download this PowerPoint
   1. Add slides as an introduction to the motherboard
   2. Identify each numbered component on the motherboard
   3. Explain (1-2 lines) what each component is

Using Logic Gates

Time to put your knowledge of logic gates and flip-flops to the test.  You will complete the assignment attached here.  Be sure to read all instructions carefully.  If you are ever unclear about the direction, be sure to ask  either in the comment section or below or in class.  You will be using the Atanua logic simulator to build and test your circuits.  When using a flip flop, you may use the “built-in” flip flops,  as opposed to constructing them from gates.

DUE:

Thursday Feb 21

History of Computers February 14, 2008

We have a bit of knowledge of how a computer stores numbers conceptually.  But before we move ahead, we should look at where we came from.  And be “we” I mean computers.  Take a look at this powerpoint presentation to get an introduction in to the history of computers.

JK & T Flip-Flops February 13, 2008

Introduction – JK Flip-Flop

A JK flip-flop is a refinement of the SR flip-flop in that the indeterminate state of the SR type is defined in the JK type. If you remember, sometimes are outputs on the SR flip-fop looked all screwy; this was because it was in an indeterminate state.

Inputs J and K behave like inputs S and R to set and clear the flip-flop (note that in a JK flip-flop, the letter J is for set and the letter K is for clear). When logic 1 inputs are applied to both J and K simultaneously, the flip-flop switches to its complement state, ie., if Q=1, it switches to Q=0 and vice versa.   In that way it is like a toggle.

A clocked JK flip-flop is shown below. Output Q is ANDed with K and CP inputs so that the flip-flop is cleared during a clock pulse only if Q was previously 1. Similarly, ouput Q’ is ANDed with J and CP inputs so that the flip-flop is set with a clock pulse only if Q’ was previously 1.

Note that because of the feedback connection in the JK flip-flop, a CP signal which remains a 1 (while J=K=1) after the outputs have been complemented once will cause repeated and continuous transitions of the outputs. To avoid this, the clock pulses must have a time duration less than the propagation delay through the flip-flop. The restriction on the pulse width can be eliminated with a master-slave or edge-triggered construction. The same reasoning also applies to the T flip-flop presented next.

 Figure 6

T Flip-Flop

The T flip flop is really just a single input jk flip flop.  To make one, we just have to hook up the wires to a single input.

Source: http://wearcam.org/ece385/lectureflipflops/flipflops/

Curcuit Building February 12, 2008

Download the simulation softwware from yeterdays post.  Once you unzip the software, open the.exe file.  If it is blocked, rename the exe file to “Notepad” and the software will run.

1.  Construct RS latch
2. Construct D flip flop
3. Construct JK flip flop
4. Save each sim as a seperate file
5. Record the truth tables for the different inputs