Component Overview: LED (Light Emitting Diode)

Component Overview: LED (Light Emitting Diode)

  February 12, 2017    Aniruddha

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What is LED?

LED or Light Emitting Diode is an electronic component that emits light when current passes through it in one direction. It will not allow the current to pass through in the other direction.

Fig 1. Standard Green, Yellow, Red LED

If a current more than its threshold is applied to it in either direction, the LED will burn out.

How to identify the correct direction of the current flow.

LED has two leads, usually of different length,  The longer lead is called the anode (+ve) and the shorter leg is called cathode (-ve). On a circuit the LED should be assembled such that the current enters from the anode and exits through the cathode.

Another way to identify a standard LED is look the LED from the top. The anode is of the smaller width than the cathode.  If you look an LED from the side you can see an arrow in which the current can flow.

Fig. 2 From top to bottom: Top view, Side view and symbol for LED

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Component Overview: Resistor

Component Overview: Resistor

  February 11, 2017    Aniruddha

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What is a resistor?

An electronic component that resists the flow of current is called a resistor.  Almost all components offer resistance. A copper wire has close to zero resistance while the resistance of the air is close to infinity.  Resistors are a common component of all electronic and electrical circuits. The most common resistor available is the axial lead resistor as shown in Fig 1.

Fig 1. 220 ohm resistor with 5% tolerance

How to know a resistor value?

Most electronic components use color coding to mark the value of the component. The resistor follow the same technique. Fig 1. shows a regular resistor.  Usually it has 4 bands of various colors which needs to be decoded to get the resistor values.  Though it is not a very efficient way, it works very well for electronic components has they are very small and printing the actual value on the component may be very small and unreadable causing confusion.

To decode the value of resistor, first get the value of each bands on the resistor using the reference table below.  For the resistor in Fig 1. the bonds from left to right are red, red, black and gold.  Looking up the values we get 2, 2, 0, 5 which would translate in 22 x 10⁰ - 5%, which is 220Ω with 5% tolerance.

What is tolerance?  It means that the actual value of the resistor will be anywhere between 5% of the decoded value.  For the above resistor, it can be anywhere between 209 and 231.

For a 5 band resistor, the 4th band is the multiplier and the 5th band is the tolerance value

More precise the resistor value you need for your circuit, the less the tolerance value you should go for. Consequently the expensive the resistor will be.

Seeing the color on a small resistor can be difficult most of the times. Hence it is better to measure the resistance value using the multimeter before you put it in your circuit

Ring color			Significant figures	Multiplier		Tolerance		Temperature coefficient
Name	Code	RAL				Percent	Letter	ppm/K	Letter
None	–	–	–	–		±20%	M	–
Pink	PK	3015	–	×10−3[5]	×0.001	–		–
Silver	SR	–	–	×10−2	×0.01	±10%	K	–
Gold	GD	–	–	×10−1	×0.1	±5%	J	–
Black	BK	9005	0	×100	×1	–		250	U
Brown	BN	8003	1	×101	×10	±1%	F	100	S
Red	RD	3000	2	×102	×100	±2%	G	50	R
Orange	OG	2003	3	×103	×1000	–		15	P
Yellow	YE	1021	4	×104	×10000	±5%	–	25	Q
Green	GN	6018	5	×105	×100000	±0.5%	D	20	Z
Blue	BU	5015	6	×106	×1000000	±0.25%	C	10	Z
Violet	VT	4005	7	×107	×10000000	±0.1%	B	5	M
Gray	GY	7000	8	×108	×100000000	±0.05% ±10%	A	1	K
White	WH	1013	9	×109	×1000000000	–		–

Table 1. The standard color code per IEC 60062:2016

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Component Overview: Breadboard

Component Overview: Breadboard

  February 04, 2017    Aniruddha

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What is breadboard?

Breadboard is a construction base used for prototyping of electronics.  It looks like a rectangular plastic board with lots of holes on it.  The Fig 1 shows a breadboard from top.

Why is it called a breadboard?

In the early days, when people wanted to construct a prototype they would do so on a flat wooden board by driving nails into it and then wrapping wires around the nails to connect to the various components.  A flat wooden board that was most handy in those days was an actual bread board on which bread was sliced. As components become smaller and electronics become more popular people started improving their prototyping base.  In the 1970s, solderless protoying board was invented. As soldering was not required, this board could be easily reused and become popular. However the name stuck from the early days of electronics.

Internals of breadboard

The internal connections of breadboard are straight forward.  The green lines in Fig 1 shows the internal connections of a breadboard. It shows a half+ size breadboard.  

Fig 1. Breadboard internal connection

The set of 5 holes as show in the diagram above are connected with other. except the sets which make up the horizontal line. This set of 5 holes are called terminal strips. This is where all the components go in. The horizontal lines on the top and the bottom of the bread board are called bus lines and the whole horizontal line is connected.  These are usually used to power the components. All the holes take in the 24 AWG size wires.  These wires are called jump wires.

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