Sunday, July 25, 2010

experiment 2 "Diodes"

THIS DIAGRAM SHOWS THE OPERATION OF A BRIDGE RECTIFIER AS IT CONVERTS AC TO DC

DIODES TAKE 0.7V TO BECOME ACTIVE IF YOU PERFORM A V/D ACROSS DIODE AND FOR EXAMPLE IT READS
O.V THIS WOULD INDICATE A SHORT


In order to identify the ANODE and CATHODE this would normally be identafiable by a bar going around the diode.

A diode has the characteristics of a INSULATOR when current tries to flow in the 1 direction or a CONDUCTOR when the current flows in the other. 

The Anode end is represented by the + sign and the Cathode by the - sign in the diagrams provided above 


Below is the LIGHT EMMITING DIODE more commonly known as the L.E.D
                                                                            
L.E.Dz are reasonabally easy to distinguish the difference between the Anode Cathode sides..the Cathode side generally has a shorter leg to the Anode,.

experiment 1 "RESISTORS"

                                                   RESISTOR COLOUR CODE CHART

Demonstrating an understanding of resistors and there values...this is made easy by the use of the colour chart and a multi meter....

 A commonly asked ? is which end you start to read the band from this is easy if there is a gold or silver band at either end if there isn't one you would start at the side that is grouped up closely together if there is this means you keep that colour to the right and start reading  from the left..The gold and silver bands represent ..tolerance and co-efficiency.

When the resistors are put into a series there values can be added together to create a greater resistance level basically you just add the resistances together to get total resistance level.

But when put into a parralel connection for example if i had 3 resistors
A 100 ohms
B 235 ohms
C 220 ohms
this would be calculated as below

1/rt = 1/100 + 1/235 + 1/220 = 0.018

1/rt = 1/0.018

RT = 53.1 ohms

This has given you a total resistance level of 53 ohms which is correct as it should be lower than the lowest resistor used.

I tested  6 different resistors and applied this formula above to determine there values in parallel and series connections.


For example a resistor with

3 BANDS

ORANGE-ORANGE-BROWN has a value of   (330 ohms)

4 BANDS

RED-YELLOW-ORANGE-GOLD has a value of (24k-ohms 5%)

5 BANDS

RED-YELLOW-ORANGE-BLACK-BROWN

But if you come across a resistor with 5 bands for example

BROWN-YELLOW-BLACK-GOLD-RED

This resistor is calculated with the 4band rule ignoring the red.