Displaying Numbers Using a Homemade Arduino Mini Shield!

In this instructable i will be showing you  how to control numeric displays(image below) using only 4 pins [excluding power(V+ and gnd)].
This uses a 4511 decoder ic  which i soldered onto a perfboard ,with a bunch of resistors and the wires and of course the numeric display ,and  finally a bunch of headers which makes it insertable into the headers of the arduino on one side thus making it somewhat of a mini shield.
The 4511 decoder IC:
The 4511 decoder ic is a BCD to 7 segment decoder (or)binary coded decimal to 7 segment display decoder.What it basically does is translate binary coded decimal in the form of 1's and 0's(for eg 0010)  into decimal(for eg 2) and displays it using the numeric display.For eg say the input in BCD  is 0011,and is translated into decimal=3 and is displayed on the numeric display.For more information about binary numbers visit:
http://en.wikipedia.org/wiki/Binary_number

for more information and projects about the 4511 ic visit:
http://www.doctronics.co.uk/4511.htm

if you want the datasheet visit:
http://www.alldatasheet.com/view.jsp?Searchword=4511BCN

This project is low cost and does not use much parts or any complicated components and is therefore easy.

Step 1: Components/Parts/Tools You Will Need:

You will need the following components:
Resistors:
 x7 numbers                 -100 ohm/47 ohm . any one value will do .They are just current limiting resistors for the numeric display.
 x4 numbers                 -10 k ohm /1 k ohm .They are pull down resistors *  for the BCD inputs
 x1 number                   -numeric display(7 segment display,this should be common cathode). This is one of the two most important components required for this project.
 x1 number                   -ic socket .This protects the ic instead of soldering it and acts as a easy replacement method in case of bad chips
x6  numbers                 -male headers.this is highly necessary as this is what makes the mini shield insert able into the arduino

You will need the following parts :
-some  wires 
-a pcb board according to your requirement (mine was 2x2 inches)

You will need the following tools:

-a soldering iron
-soldering lead
-optional:a de soldering pump or some copper braid for removing solder 

*pull down resistors:
in some ic's if the inputs are not pulled down to ground ,the ic will take the value for the input as high(in this case 5v)

Step 2: The Build!

above i have given you the schematic for building the shield and make sure you do not connect wires that appear to be connected in the schematic.If you are not able able to differentiate between connected and unconnected wires ,just google "how to differentiate between connected and unconnected wires in a schematic".Also in case of solder overflow on unconnected joints use a de soldering pump or copper braid/wick to remove it and re solder it again.While soldering the headers make sure they don not touch or are not connected.the pull down resistors all are connected to ground and so is pin5.Pin 5 is latch enable which allows you to display different digits consecutively(one after the other).pin 16 is V+ and pin8 is V-..In the diagram the headers have to be connected in the following order from left to right :
1-gnd (goes to the gnd pin near pin 13)
2-V+ (goes to pin 13,it should always be set to high as it acts as the V+ for the shield here)
3-bcd input A(goes to pin 12 of the arduino)
4-bcd input B(goes to pin 11 of the arduino)
5-bcd input C(goes to pin 10 of the arduino)
6-bcd input D(goes to pin 9 of the arduino)
also always use an ic socket and don't solder the ic directly onto the board as this may resulting in making the shield not work.Most of all make sure you pry the header row to its end point so you get more space for soldering.if you don't understand post a comment and i will upload an image.Good luck on making it.

Step 3: Tips Tricks,Precautions and Sources of Error!

Tips and tricks:
you can add another chip to the same shield(of course you'll have to make the board bigger) and use 2 numeric displays and then you can display 2 digit numbers,this can be done by replicating the circuit exactly on a bigger board twice.Also by adding headers you can even plug it into a breadboard.from the breadboard you can extend the pins by adding jumpers and the connect it to whatever you want.This shield happens to work with different ranges of voltages(4.5v -12/15v) and is not restricted by the 5v limit

Precautions and sources of error;
make sure while soldering the headers you do not solder them together by mistake.Make sure you solder the inputs for the ic to the headers A,B,C,D respectively from the left side after gnd and V+ respectively  to the right side.Check to find if you have connected the pins of the 4511 ic to its corresponding pins on the 7 segment display ic. Installing the chip in the wrong way in the  wrong way or reversly can make the shield not work.

Most of all thank you for viewing my instructable and please correct me if i'm wrong in it and don't forget to comment below
and if you have any doubts comment below once again.