HOW TO CALCULATE RESISTOR & CERAMIC CAPACITOR VALUE.

You all must have had a problem while make your projects and searching old pieces of circuits for a particular resistor or a capacitor.

Well , using a multimeter is a good option but  it may not be available to most of us, and using it is a bit complicated and I will be posting it in  my next instructable on it.

Presently, I will tell you the criterion for calculating the resistance and capacitance.(Only in ceramic capacitors as it is mentioned on electrolytic capacitors)

Step 1: MOTIVATION

I was making a school project and I needed some resistors and capacitors, as the local electronics shop is about 20km from my house saw I started to look in the old circuit boards I have.

As I didn't have a multimeter so I tried to understand the logic behind the codes.

Which I will be telling you.

Step 2: THE RESISTOR

First, of all I would Like to start off with a few basics.
For those of you who don't know what is a resistor, it is device that resists the flow of current.

The colour code is just, the resistance in the forms of  coloured strips.
The colours include-

1. BLACK
2. BROWN
3. RED
4. ORANGE
5. YELLOW
6  GREEN
7 .BLUE 
8. VIOLET
9. GREY
10.WHITE

Now, the first two strips of the resistor represent the digit and the third is the multipier band .
And the fourth band gives the tolerance.

The image is from  --http://www.doctronics.co.uk/resistor.htm

Step 3: CALCULATING RESISTANCE

First,  of all I would like to give you a table so that you can calculate the resistance and tolerance.
                                                                                                                                            RESISTANCE
Now, if the first strip is brown in colour then it indicates that the fist number is 1.                1
Again, if the second strip is black then the second digit is 0.                                                10
The third strip is orange,as orange is third in the table,there will be 3 zeroes.                     10 X 1000
                                                                                  TOTAL RESISTANCE           10,000 Ohms


                                                                                                                                        RESISTANCE

Example, like in the picture           FIRST BAND= YELLOW                                            5
                                                   SECOND BAND= VIOLET                                            57
                                                        THIRD BAND=  RED                                                57x100

                                                 TOTAL RESISTANCE                                                    57,000 Ohm
Now comes the tolerance. well it is the variation inresistance.

If it is +5% then the resistance can be 5% more.

EXAMPLE- Like if it is golden in the picture the resistance  can be   _+5% of the resistance.
                                                                                                                                     57000 X 5/100
                                                                                                                                  = 2850 ohm
The resistance hence can be 57,000 +5%= 59,850 Ohm
                                               57,000-5%  = 54150 Ohm


The images are from --http://www.doctronics.co.uk/resistor.htm

Step 4: THE FIVE BAND RESISTOR

In a five band resistor there are 5 bands instead of four.

The first three digit represent the numbers and the fouth one is the multiplier band.

Foe Example- A 100 Ohm reistor will be code as BROWN BLACK BROWN  in four band resistor.
       Whereas  it will be coded as BROWN BLACK BLACK BLACK in five band coding.

The image is taken from -  lgreen1661.blogspot.com

Step 5: FAQ'S

Here are a few FAQ'S often asked about resistors-
Q1) What is a resistor?

Ans)Resistors are small electronic devices that resist the flow of electrical current. A resistor obeys Ohm's Law, which states that the voltage (or potential) across a resistor is proportional to the current flow through the resistor. In formula form, V=IR, where V is the voltage across the resistor, R is the value of the resistor in ohms, and I is the current flow through the resistor in amperes (amps).

Q2)What are the types of resistor?

Ans) There are basically five types of resistor-
         a. Fixed value resistor
         b. Variable resistor
         c. Potentiometer (adjustable resistor)
         d. Thermistor (temperature variable resistor)
         e. Photo resistor

Q3)Which side of the resistor do I read from?

Ans)The Gold or Silver band is always set to the right, then you read from left to right. Sometimes there will be no tolerance band -- Simply find the side that has a band closest to a lead and make that the first band.

Q4) Sometimes the colors are hard to make out. How do I make certain what the value of the resistor really is?

Ans)Occasionally the colors are jumbled or burnt off. The only way to read it then is with a multi-meter across the leads

Q5) How do I remember this sequence of colors?

Ans)Remember the color codes with this sentence:
Big                 - BLACK
Brown            - BROWN
Rabbits          - RED
Often             - ORANGE
Yield              - YELLOW
Great             - GREEN
Big                 - BLUE
Vocal             - VIOLET
Groans          - GREY       
When            - WHITE
Gingerly        - GOLD
Slapped.       - SILVER

Step 6: CALCULATING CAPACITANCE

The first two digits of a ceramic ceramic capacitor tells us the capacitance in uF and the next digit tells us the negative power.

Like, if it says 103 then it means it is 10 uF X 10 ^-3.

Therefore, 0.01uF.

Like in the picture the code says 154. So, it means 15 uF X  10^-4     =   0.0015 uF .

I have also uploaded a conversion table so that you can convert the  units from one to another.


The image for the ceramic capacitor is from-      electro-tech-online.com
The conversion table is from -  mechatrotutor.blogspot.com