PB 6th IntroductoryInterfac ingAndElectronics

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Introductory Interfacing & Electronics: 

Introductory Interfacing & Electronics Peter Beens peter@beens.org Presented at Durham College November, 2004

Overview: 

Overview This presentation covers a basic introduction to interfacing with the parallel port and just enough electronics to keep you from damaging your computer.

Interfacing Introduction: 

Interfacing Introduction

Interfacing Overview: 

Interfacing Overview Computer Interface Peripheral Wires ICs Resistors Capacitors Transistors Connectors LEDs Motors Lights Robots Joystick Music Box

What Ports Can We Interface?: 

What Ports Can We Interface? Parallel Port (AKA Printer Port) Serial Port (AKA RS232) Keyboard Port USB??? (Hopefully soon…) We will concentrate on the Parallel Port

Identifying the Parallel Port: 

Identifying the Parallel Port It’s the female connector with 25 pins “DB25” Can be on a card

Electronics Introduction: 

Electronics Introduction

Three Main Invisible Electrical Properties: 

Three Main Invisible Electrical Properties Voltage, V, Volts Provides the “push” Current, I, Amperes (Amps) Flow of Electrons Amount of Current is dependent on Voltage and Resistance Resistance, R, Ohms (S) Limits the amount of current

Safe Current & Voltage Levels: 

Safe Current & Voltage Levels Voltage: 30 V Voltages inside a computer do not exceed 12 V, except at the power supply and power switch on older computers, which are at 120 V. Be careful in these areas! Current: 5 mA (0.005 Amperes)

Voltage Sources: 

Voltage Sources

Current: 

Current Is the flow of electrons Direction depends on convention

Ohm’s Law: 

Ohm’s Law “Current (I) is proportional to Voltage (V) and inversely proportional to Resistance (R)”

Ohm’s Law & Power Wheel: 

Ohm’s Law & Power Wheel Reproduced by permission of Tony van Roon, 2002 http://www.uoguelph.ca/~antoon

Kirchhoff’s Laws: 

Kirchhoff’s Laws Kirchhoff’s Voltage Law “The sum of the voltage drops equals the applied voltage”, or… “The sum of the voltage drops around a closed loop equals zero” Used in series circuits Kirchhoff’s Current Law “The current entering a junction must equal the current leaving the junction” Use in parallel circuits.

Light Emitting Diodes (LEDs): 

Light Emitting Diodes (LEDs) A type of diode designed to emit light Can be visible or IR 2 V voltage drop Typically draws 20 mA (0.020 A) Schematic Symbol…

Resistors: 

Resistors Can be rated by… Resistance (Ohms, S) Tolerance (% of nominal value) Power Rating (Watts) Schematic Symbol…

Resistor Types: 

Resistor Types

Resistor Colour Code: 

Resistor Colour Code Reproduced by permission of Tony van Roon, 2002 http://www.uoguelph.ca/~antoon

Resistor Colour Code Example: 

Resistor Colour Code Example 1st band: orange = 3 2nd band: orange = 3 3rd band: red = 2 (i.e. 102) 4th band: gold = 5% 33 x 102 = 3300 S = 3.3 kS

Resistor Power Ratings: 

Resistor Power Ratings

Series Circuits: 

Series Circuits One current path, therefore the current is the same everywhere Total resistance is the sum of the individual resistances

Parallel Circuits: 

Parallel Circuits More than one current path Total current is the sum of the individual currents

The Parallel Port – The Hardware: 

The Parallel Port – The Hardware

Parallel Port Specifications: 

Parallel Port Specifications Output Voltage 0V for “low” 5V for “high” TTL (Transistor-Transistor Logic) Output Current Limitation 10-15 mA (careful!)

Parallel Port Pinout: 

Parallel Port Pinout Graphic from http://www.doc.ic.ac.uk/~ih/doc/par/

Output Table: 

Output Table

Input Table: 

Input Table

Interfacing an LED Circuit: 

Interfacing an LED Circuit

Understanding the LED Circuit: 

Understanding the LED Circuit The parallel port output is 5V A standard red LED needs ~20 mA and drops about 2 V A resistor is needed to “drop” the excess voltage

Doing the Math: 

Doing the Math From Ohm’s Law From Kirchhoff’s Voltage Law Currents equal in a series cct

Motor Control: 

Motor Control (A stepper motor would require more outputs)

High Current Control: 

High Current Control Use a relay

Parallel Port Connector Tip: 

Parallel Port Connector Tip

The Programming: 

The Programming

Turing: Preparing for Interfacing: 

Turing: Preparing for Interfacing Turing is already prepared for interfacing with the parallel port No preparation necessary!

Turing: Turning On the LED: 

Turing: Turning On the LED Parallelput(value) Parallelput(1) turns on the 1 bit (D0) Parallelput(255) turns on all bits (D0-D7)

Turing: Turning Off the LED: 

Turing: Turning Off the LED Parallelput(0)

Turing: Flashing the LED: 

Turing: Flashing the LED loop parallelput (1) delay (250) parallelput (0) delay (250) end loop

Turing: LED Walking: 

Turing: LED Walking loop % loops up for i : 0 .. 7 parallelput (2 ** i) delay (500) end for % loops down for decreasing i : 6 .. 1 parallelput (2 ** i) delay (500) end for end loop

Java: Preparing for Interfacing: 

Java: Preparing for Interfacing Download http://www.geocities.com/Juanga69/parport/parport-win32.zip Extract the parport folder to your classes folder Copy parport.dll to you bin folder import parport.ParallelPort; ParallelPort lpt1 = new ParallelPort (0x378);

Java: Output: 

Java: Output ParallelPort lpt1 = new ParallelPort(0x378); int byteVal = 255; lpt1.write(byteVal); System.out.println("Output to port: " + byteVal);

Java: Input: 

Java: Input ParallelPort portIn = new ParallelPort (0x378); int in; in = portIn.read (); System.out.println (in + " is currently being input.");

Java Delay Method: 

Java Delay Method private static void delay (int mS) { try { Thread.sleep (mS); } catch (Exception e) { ; } }

Delphi: Preparing for Interfacing: 

Delphi: Preparing for Interfacing Download io.dll from http://geekhideout.com/downloads/io.dll Copy into project folder

Delphi: Output: 

Delphi: Output procedure PortOut(Port : Word; Data : Byte); stdcall; external 'io.dll'; procedure TForm1.Button1Click(Sender: TObject); begin PortOut(888,1); end;

Delphi: Input: 

Delphi: Input function PortIn(Port:Word):Byte; stdcall; external 'io.dll'; procedure TForm1.Button3Click(Sender: TObject); var InValue : Byte; begin InValue := PortIn(889); label1.Caption := IntToStr(InValue); end;

Delphi Delay Procedure: 

Delphi Delay Procedure procedure xSleep(milliseconds: LongInt); var iTemp : Longint; Begin iTemp:= GetTickCount + milliseconds; while GetTickCount < iTemp do Application.ProcessMessages End;

Assembler: Output: 

Assembler: Output MOV DX,0378H MOV AL,n OUT DX,AL Where n is the value you want to output.

Resources: 

Resources

Web Resources: 

Web Resources http://www.epanorama.net/circuits/parallel_output.html http://www.lvr.com/jansfaq.htm http://www.doc.ic.ac.uk/~ih/doc/par/ http://www.southwest.com.au/~jfuller/delphi/delphi1.htm

Textbook References: 

Textbook References Computer Engineering: An Activity-Based Approach (Holt) Networks, Interfaces and Integrated Circuits (Holt)

Q: Why can't programmers tell the difference between Christmas and Halloween? : 

Q: Why can't programmers tell the difference between Christmas and Halloween? A: Because DEC25 = OCT31

Contact Information: 

Contact Information Pete Beens Westlane Secondary School Niagara Falls, ON L2H1T5 905.356.2401 Web: http://www.beens.org Email: peter@beens.org