Basic Components - Capacitor

Capacitors:

A basic capacitor based circuit:

Demo:

Basic Components - Resistors

Resistor: 

As we had seen in the basic circuit, addition of a resistor in the circuit limited the flow of current. This was indicated by the LED glowing dimmer when a resistor was introduced. It is obvious that higher resistance limits current flow to the maximum. This can be observed by playing around using different resistors.

Identifying Resistor values:

Resistor value is identified by the colour code in it. There are many sites that teach you how to calculate the value of a resistor. 

Color                         Value

Black                          0                                      
Brown                         1                                     
Red                             2                                     
Orange                        3                                     
Yellow                         4                                      
Green                         5                                       
Blue                            6                                       
Violet                          7                                       
Grey                           8                                       
White                          9                                      

Gold / Silver colour at the end indicate the tolerance of resistor and are +/- 5% and +/- 10% respectively. This indicates that the value of resistor used will be within the range R-5% to R+5% if it has a gold band.

In case of tri-band resistor, the first 2 colour bands indicate the significant digits and the last colour band indicate multiplier.

In case of 4/5 band resistor, the last colour band indicates the multiplier and a similar calculation can be used to compute resistor value.

Example:

Lets quickly identify the value of a resistor that is coloured in the following order

Black                          0                                      
Brown                         1                                     
Red                             2                                     


=(10) X (100)
=1000 Ohm
=1Kilo Ohm

Yellow                         4                                     
Violet                          7                                      
Red                             2                                                 



=(47) X (100)
=4700 Ohm
=4.7 Kilo Ohm

Basic Components - Battery

Battery:

Battery is the one of the sources of power that can be used to drive a circuit. While designing a circuit, we should be able to decide on the rating of battery to be used based on the circuit parameters. Generally there are 2 key parameters that are needed for battery selection.

1. The current drawn by the circuit
2. How long the circuit will be in use before fully draining the battery.

For example: lets say a circuit draws a current of 1 micro-Ampere, and the batter is required to last for 1 full year. Multiply both 

capacity needed = (1 micro ampere) x (24 hours x 365 days) = 0.00876 ampere Hours

Lets account some 30% for losses, so add 30% of 0.00876 which gives (0.00876 + 0.002628) = 0.011388 ampere Hours. This is roughly 11.4 milli-ampere Hours.

In the previous experiment, we used a CR2032 cell. If you do a quick search for its specifications, you can know the following.

• It is a 3V cell 
• It has a capacity of 225mAh at 200 micro Amperes. 

The capacity of a battery is indicated in the format of [current]x[time]. In case of CR2032 3V Cell, capacity is 225mAh. Now you can imagine, how long this cell can last when used in a circuit that draws low current (1 micro ampere). Probably you will now be able to understand better why CR2032 cell is used in PCs for CMOS. Roughly these batteries should last for more than 2-3 years as they are used in a circuit that draws low current.

So, if  we are able to specify the current that can be drawn by our circuit and the time frame for which we want the battery to last, we should be able to select appropriate battery.

To give another example, you must have observed AA batteries used for Wall Clocks/ Television Remote Controls.  The specifications of AA batteries are given here. The capacity ranges from 400 mAh to 3400 mAh. An average capacity of around 2000 mAh should last for 2-3 years for a low power circuit.

Getting started

Lets get quickly started into this. I will list below the basic things that are needed. Managed to get these stuff from a local electronics shop. We require the following basic things to get started

Power source:  

  This is the most primary requirement. I was looking for something handy and thought of this. It is a 3V CR 2032 cell. You can use any battery or a power adapter if you prefer. The holders are perfect and can be directly be inserted to a bread board. 

3V cell holder front and back views, a 3V cell

Bread board:

    This is where we are going to plug all our components and experiment things. The holes in a column are connected. The top and bottom areas can be used to connect to battery + and - or cases that require multiple connections.

Bread board

LEDs:

Light Emitting Diodes are very useful since they can serve as indicator of the circuit behaviour. Note that LED allows current to flow in only one direction. This is a property of diode and LEDs are diodes that emit light.

LED

Switch:

It is good to have a switch in the circuit as we can check once whether all connections are correct and then power the circuit using switch. There are many varieties of switches available. I am going to use a push switch for now.

a push switch

A basic circuit: 

Lets get started, with a basic circuit. Connect the battery, switch and  LED as shown in the figure.

Keeping the circuit in mind, lets connect things onto the board one by one. Be ready for the show.

Basic circuit

Placing the battery holder onto the board was a bit difficult and it takes up space. Probably I will solder wires onto the holder. The circuit is fairly simple. Time to turn it on. Make sure you have connected the LED in the correct manner. LED allows current only in one direction. chances are that you have connected it wrongly. If everything  is okay you should see a glow when the switch is pushed.

Too much bright for a little LED !! Now lets starve him by feeding him lesser. Here comes the resistor!

Resistor:

Resistors are components that act as a barrier for current flow.

Lets introduce a resistor in the circuit and see the effect.

Key Understandings:

1. Usage of few basic components (cell, bread board, LED, switch, resistor)
2. Attribute of resistor - limits flow of current.

Electronics step by step

I took up 'Electronics and Communication Engineering' after completing school education. I imagined myself as someone who would be playing around with wires, boards, transistors, capacitors and ICs after completing the engineering degree. However that did not happen and I landed up in a programming job. It had been more than eight years after that. Many a times I had felt that I have missed a lot of fun and thrill which I look forward to have now. I will experiment with all sorts of components and post details on these step by step. Hope we are going to have fun !