*introduction

It is common to have a lot of  resistors and you want a specific value but you don't memorize the resistor color code  .

In this project I tried to solve this problem by making a circuit using Arduino and some components which allows you to enter the value of resistor and have the color code as an output in more than one method:
on serial monitor (Arduino IDE).
Using 3 RGB LEDs.

You can input the values using:serial monitor or by using Keypad.

Building the project

*part list

Arduino or any compatible device /1/ (I used a clone named SHAMduino we produce in the company I works at named Atadiat ).
Keypad /1/.
RGB LEDs /3/.
Demultiplexer CD4053 /2/ .
Seven segments 3 digits /1/
Seven segment driver HEF4543B /1/.
Resistor 470 ohm /12/.
Testboard /1/.
Wires and jumpers.

*Hardware details:

**Arduino:
Moist of you know this popular platform which I find the best choice for building fast prototypes, before switching to raw electronics using microcontrollers and PCBs.

**Keypad:
this component is the input device of this project which consist of raws and columns (ex:4×4) , the numbers of pins is equal to the numbers of  raws+columns.

**RGB LED:
this kind of RGB LED is consist of internal leds which are:red,green and blue . we can produce any color we want using mix of Red ,Green and Blue.
For example if we want to have a white color we must switch on the 3 internal leds.

(NOTE: there is 2 types of RGB led common anode and common cathode )  

**Demultiplexer:
You will see that the pins of Arduino will run-out, so I must reduce the number of used pins, so I used a demultiplexer  for this purpose. With using this demultiplexer I will need 3 pins as  output for RED , green and blue pins if the RGB LEDs , 1 pin for selecting channel inside every chip and 2 pin to avtice/de-active chips .Without using this demultiplexer I will need 9 pins to drive the RGB LEDs.

If you don't know what demultiplexer is, you can imagine it as a switch, which can switch between to channel every channel have 3 input/output , with common input .

The reason  I used 2 of CD4053 is that every chip have 2 channel  and I need 3 triple channel ,so I used 2 of them.

So when I need to output some color the enable loop will be like this :

channel 1 chip 1 (on)
channel 2 chip 1 (off)
chip 2 (off)

channel 1 chip 1 (off)
channel 2 chip 1 (on)
chip 2 (off)

chip 1 (off)
channel 1 chip 2 (on)


**Seven segment driver :
Also I used the driver to reduce the number of  required pins to drive 7seg  from 7 to 4 pins .
One more feature about  HEF4543B is than I can control the output of this chip if I have common anode or cathode 7seg .

The reason behind using 7seg is for future development, to make the device portable and see the entry using 7seg.


*Software details:

The sketch behind this project is consist of the following functions 

 seven_seg_disp(int num)
rgbled(int r,int g,int b)
colortorgb(int color)
rgbdisp()
printbandcolor(int band)
value()
start()

Before explain every function lets understand the code and how it works.

First in the loop function you can see  a while loop with condition DO==TRUE. DO is a key for execution , with initial value FALSE .If user didn't finish correctly the input DO will change to true. keys is important to make sure that some codes doesn't execute unless I unlock the key.
Then you will find 2 structures:first is IF and the second is FOR, IF is used to make sure that FOR doesn't execute unless user press '*', which make DO2 (the key of  FOR loop) TRUE. These tow structure is dedicated to keypad input method. 
In the FOR loop user may finish the entry by pressing '*' tow times, because some times we have one digit like 1 ohm.
You can see in both input method(keypad and serial monitor) that I used a counter 'numofdigits' the reason is related to manipulating the entered values (in function value()). 
Input from keypad or computer is coded using “ASCII” so to get the real value we must subtract it from '0' value in ASCII.

Now lets talk about every function:

seven_seg_disp(int num)
		Output the D0-D3 on Arduino pins connected to 7seg driver.
rgbled(int r,int g,int b)
		Output the arguments to RGB pins connected to Arduino.
colortorgb(int color)
		Convert numeric value of resistor bands to RGB color.
rgbdisp()
		Output function for both 7seg or RGB leds ,it activated and deactivate demultiplexers 			and channels  alternatively. 
printbandcolor(int band)
		Printing the color code of every band on Serial monitor.
Value()
		Manipulating entered values according to possibilities  of entries and store the values in  		matrix called colorcode.
start()
		To make sure that some values return to initial value especially digits matrix which is 			used for entry and must by blank every time we enter new values.