Computer Hardware Technology

ELECTROBOT PROJECT

Computer Technology: ELECTROBOT• Task: Teams of 2 will design and build an electronic

control system for a 4 LED display mask. The controller will then be used to guide a team member wearing the mask through a maze. The goal is to pick up an object in the least amount of time.

• Requirements:– Project report: description, diagram and parts list– Safety notes– Build mask and controller, following tool procedures– Complete a timed race through the maze

Finding the Value of a Resistor by Color Codes

• Step One: Turn the resistor so that the gold or silver stripe is at the right end of the resistor.

• Step Two: Look at the color of the first two stripes on the left end. These correspond to the first two digits of the resistor value. Use the colour table given to determine the first two digits.

• Step Three: Look at the third stripe from the left. This corresponds to the multiplier (# of 0’s to add).

Practice this with real resistors!

Electricity Theory – Pressure & Flow

Basic Measures of Electricity• V- electrical pressure measured in volts (V)• I - current flow measured in amperes (A)• R- resistance measured in ohms (symbol Ω)

Ohm's Law: V = I x R

if you know any 2 values in a circuit you can calculate the other value

* Note - Another important measure is Power: P= I x V (in watts)

Resistors• Used to control

current (I) or voltage (V)

• maximum power level measured in watts (V x I) depends on material inside & physical size

• resistance value in units of OHMS based on colour coded stripes for small resistors

• BBROYGBGW…

Resistor Colour CodingNumber Colour

0 black

1 brown

2 red

3 orange

4 yellow

5 green

6 blue

7 violet

8 grey

9 white

• Colour bands are assigned number values to determine the ohm value…

LED – Light Emitting Diode• LED uses V = 2 volts• Works best at I = 10- 20mA• Must use a resistor R to

limit the current or it will burn out.

• Calculate R needed if Vsupply = 9 volts (ohm’s law)– R = (V Supply - VLED) / I

symbol+ -

– current only flows from + to - lead

Parts & Schematic Diagram

Parts:• 4 LEDs• 470 ohm resistor • Copper tape• 5 wires• 9 volt battery• Battery terminal• Cardboard

9 volts DC

R = 470 ohms

Controller Mask

Tools – Use properly and safely*• Soldering iron• Safety glasses• Exhaust fan• Wire strippers – follow the demo• Wire cutters• Scissors• Digital Multimeter (DMM)

* Zero tolerance for misuse or horse play with tools and equipment

SolderingSoldering is the process of joining two metals together using a low temperature melting alloy.http://www.curiousinventor.com/guides/How_To_Solder

http://store.curiousinventor.com/guides/how_to_solder/heat_solder

http://www.sentryair.com/solder%20fume.htm

Instructor will assess solder safety and qualityGood solder joints: smooth, shiny, and filled in a concave fashion

Poor solder joints: dull, irregular shape and/or pooled in a blob

SolderingSafety Hazards

BURNS – Soldering iron tip is very hot (~350 degrees Celsius)

FUMES – Melting metal and flux produces fumes that irritate the respiratory and digestive system

SPLASH – Hot solder splashes or rosin fluxPOISON – Lead is poisonous, and flux can be

corrosive to skin

TAKE STRICT PRECAUTIONS ---- > next page

Soldering Safety Precautions1. Wear safety glasses2. Keep work areas neat and well spaced3. Hot soldering irons - move slowly4. Keep electrical cords away from iron & stand5. Fumes - work in a well ventilated area6. Do not hold parts to be soldered – use clips,

pliers, and other holding tools7. No food in the area8. Hand washing after exposure to solder9. Zero tolerance for misuse or horse play.

Building the Electrobot1. Prepare five wires of 4’ length & bundle them

– Strip 1” of insulation off both ends

2. Cut out a controller from cardboard (4” x 4”)– Fold and trim 4 switches – Place copper tape in position– Secure finished wire bundle with masking tape

3. Cut out a LED display of cardboard (3” x 3”)– Mark the + and - positions for 4 LEDs– Make pin holes for LED leads and insert them– Wrap on 1 wire to each +, then 5th wire to 4 – leads

4. Begin soldering, following correct procedures– Safety glasses, fans, holding tools correctly

Soldering Technique• Preparation

1. Use safety glasses and exhaust fan – don’t inhale any fumes

2. Place a wet sponge on the stand – clean the tip frequently

3. Place a mat down to protect the work surface

4. Electrical cord runs from front-right or left (depending on hand used)

5. Parts to be soldered must be clean

6. Soldering iron tip should be clean

7. Securely position the components to be soldered, it should not move• Application : Solder the 4” x 4” control board that has been preparedred

1. Apply heat at the joint

2. Apply solder on the other side of the joint (not on the iron)

3. Solder will flow once the joint is heated enough

4. Do NOT let solder flow for more than 1-2 seconds

5. Remove solder wire, and then remove the hot iron

6. The solder will harden very quickly