MDS975 logo RESISTOR and
CAPACITOR
TABLES
with added LED current limiting resistor calculations
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Suppliers Of Modern and Older Vintage Components

DID YOU KNOW?

Electronic component sizes have been effectively reducing by half about every 18 months over the years!
The same progress in design, manufacture and miniaturisation also enabled computer processor (CPU) speeds to be doubled every 18 months during that this time! However there is a limit to this continual increase in CPU clock speeds by using these traditional methods, and different types of processor architecture will emerge in the future.

Photo' showing some older components on the left and some newer ones on the right
The effect of miniaturisation is quite noticeable even when working with the very ordinary components involved in the construction of typical 'home-brew' projects, i.e. components with leads intended for use on an ordinary circuit board.  Typical resistors and capacitors are very much smaller now than they were 20 years ago.

This process of miniaturisation has progressed beyond the 'ordinary' components that are used in everyday home built projects and equipment built on ordinary circuit boards, since there is a limit to how small a component can be and remain useable for such work.  Today's powerful personal computers, laptops, mobile 'phones and digital cameras are made possible by the use of very large scale integrated circuits and tiny 'surface mount' components such as resistors and capacitors that are often the size of a pin head and are therfore rather more difficult to work with for the home constructor.
RESISTOR COLOUR CODES AND CAPACITOR CONVERSION TABLE

When constructing electronic projects it will be necessary to determine the exact value of resistors, which are colour coded, and capacitors, which sometimes have confusing numbers on them.  I have therefore included some tables for both Resistors and Capacitors to help identify their values.

For some simple ideas on solderless construction techniques have a look at the Crystal Sets 2 page.
RESISTOR COLOUR CODES
MDS975.CO.UK

RESISTORS WITH FOUR COLOURED BANDS

For traditional resistors there are usually FOUR coloured bands.  The first two coloured bands will show the first two digits, the third band provides the multipier by which the first two digits must be multiplied (i.e number of zeros); together this gives the value of the resistor (the resistance) in Ohms.  The fourth coloured band indicates the tolerance of the resistor, that is how close the actual resistance may be to the value indicated.  A 1k Ohm (1000 Ohm) resistor with a 20% tolerance could have a value anywhere between 800 and 1200 Ohms.

The tolerance band is sometimes spaced further apart from the other three bands, which helps when deciding which way round to read off the value, which is sometimes difficult to establish immediately.

FIRST DIGIT
First Colour Band
 SECOND DIGIT
Second Colour Band
 MULTIPLIER
Third Colour Band
BLACK
 		0 

0
x 1
BROWN
 		1  
1
x 10
RED
 2  
2
x 100
ORANGE
 3  
3
x 1,000
YELLOW
 4  
4
x 10,000
GREEN
 5  
5
x 100,000
BLUE
 6  
6
x 1,000,000
VIOLET
 7  
7
x 10,000,000
GREY
 8  
8
x 100,000,000
WHITE
 9  
9
x 1,000,000,000

Tolerance
Fourth Colour Band:
BROWN
1%
 RED  
2%   		GOLD
5%		 SILVER
10%		 SALMON
20%

Examples:
BROWN BLACK BROWN SILVER = 10 X 10  = 100 Ohms (Usually expressed as 100R) 10% Tolerance
YELLOW VIOLET RED GOLD = 47 X 100 = 4700 Ohms (Usually expressed as 4.7K) 5% Tolerance
ORANGE ORANGE YELLOW SILVER = 33 X 10,000 = 330000 Ohms (Usually expressed as 330K) 10% Tolerance
RESISTORS WITH FIVE COLOURED BANDS
A number of resistors have FIVE coloured bands to indicate their resistance value and tolerance.  The first three bands indicate the first three digits, the fourth band provides the multipier by which the first three digits must be multiplied (i.e. number of zeros) the result gives the value of the resistor. The fifth band indicates the tolerance.  Again it is often difficult to tell which way round to read off the value, but the tolerance band is usually spaced a little further apart from the first four bands.

FIRST DIGIT
First Colour Band
 SECOND DIGIT
Second Colour Band
 THIRD DIGIT
Third Colour band
 MULTIPLIER
Fourth Colour Band
BLACK
 0
0
0
x 1
BROWN
 1
1
1
x 10
RED
 2
2
2
x 100
ORANGE
 3
3
3
x 1,000
YELLOW
 4
4
4
x 10,000
GREEN
 5
5
5
x 100,000
BLUE
 6
6
6
x 1,000,000
VIOLET
 7
7
7

GREY
 8
8
8
 GOLD
 x 0.1
WHITE
 9
9
9
 SILVER
 x 0.01

Tolerance
Fifth Colour Band:
BROWN
1%









Examples:
BROWN BLACK BLACK BLACK BROWN = 100 X 0 = 100 Ohms (100R) 1% Tolerance
YELLOW VIOLET BLACK BROWN BROWN = 470 X 10 = 4700 Ohms (4.7K) 1% Tolerance
ORANGE ORANGE BLACK ORANGE BROWN = 330 X 1000 = 330000 Ohms (330K) 1% Tolerance

N.B. Five band resistors are always +/- 1% tolerance


CAPACITOR CONVERSION TABLE
MDS975.CO.UK

LARGE CAPACITORS

Electrolytic
Probably the most common large capacity capacitor is the Electrolytic type. Most Electrolytic capacitors are clearly marked with the value of the capacitor in microfarads (uF), the polarity of the leads, and the working voltage.  For this reason electrolytic capacitors are often the easiest capacitors to identify and use. 

Most electrolytic capacitors will have clearly printed on the body something like:  "220uF   50volts". It is very important to remember that most electrolytic capacitors are polarised i.e. the must be connected the correct way round in the circuit - to identify polarity these capacitors will generally  have a (usually white) stripe down one side with a  -ve sign to indicate that lead is to go only to the negative side of the circuit and the +ve lead will usually be longer than the -ve lead to help identification. Becuase DC is usually present in a circuit an electrolytic capacitor must be connected the right way round, if it is connected the wrong way round it may explode, so be careful!

Tantalum
Another type of capacitor that is available in large capacities is the Tantalum Bead type, they are much smaller than electrolytic capacitors and also usually have lower working voltages. Tantalum capacitors are also polarised and must be connected the right way round in the circuit. Modern tantalum bead capacitors have the value printed on the casing along with the voltage and polarity marking.

Older ones use a colour code in the form of stripes and a spot. The top two stripes give the first two digits - using the colours in the table below, and the spot is the multiplier: Grey Spot = x 0.01  :  White Spot = x 0.1  :  Black Spot = x 1 . The third (bottom stripe) is the voltage marking - yellow being 6.3V; black being 10V; green being 16V; blue being 20V; grey being 25V; white being 30V and pink being 35V. The positive lead is the one on the right hand side when the spot is facing you.

SMALL CAPACITORS

Small value capacitors will be unpolarised and therefore can be connected into a circuit either way around. Many circuits specify small capacitors. They are available in a wide range of values, with the various polyester types and ceramic capacitors being popular choices.  Some circuits may specify capacitor values in microfarads(uF), some in nanofarads (nF) while others may use picofarads (pF). The different and varied types of component marking used on capacitors can all be rather confusing!


PRINTED VALUES

Some capacitors simply have the value printed on them which sounds easy, but you have to know if the number is in microfarads, nanofarads or picofarads. It seems to be common that if, for example, a capacitor is marked 0.22 this means 0.22 microfarads (uF) and if the printed marking is, for example, 2n2 then this would be a 2.2nF (nanofarad) capacitor.  

SIMPLE TWO DIGIT MARKINGS

Often the capacitor will simply be marked with a two digit number printed on the body such as "10" for example.  This indicates that it is a 10pF capacitor.  However you may find some capacitors marked "10n" and this capacitor will have a value of 10nF (ie 10,000pF), this is sometimes seen on polystyrene types and some resin dipped ceramics.



CODED THREE DIGIT MARKINGS

Many capacitors use a coded marking system, and it seems that the majority of modern capacitors that I have used in recent years fall in to this category, so here is a guide:

When we get our bag full of bits through the post, or eventually arrive home from the electronics shop with our little plastic bag full of components, keen to construct a circuit we will often find that many capacitors are marked with a three digit code such as "103" or "104" and some others have a three digit code plus a letter on the end such as "101K" or "102K".  This can lead to a bit of 'head scratching' before construction of our exciting project can begin! Once we can familiarise ourselves with these codes or have a chart at hand then progress to the all important construction stage will be much swifter.

The capacitors marked with three digits are similar to resistors in that the first two digits need to be multiplied by the third digit in order to obtain the value in PICOFARADS (pF) as above. The letter is present to indicate the tolerance of the component.  So 100 would be 10pF multiplied by zero i.e. 10pF.  103 is 10pF multiplied by 1000 ie 10,000pF or to put is another way 0.01 microfarads.   471K would be a 470pF capacitor with a 10% tolerance.

Help is at hand.....

To help make sense of all this and to be able to easily convert from nF to pF to uF etc. here are a couple of very handy little tables:

Remember that the code marking, when decoded, will provide the value in Picofarads (pF), but the table below shows you the values in microfarads (uF) and nanofarads (nF) too.
CODE / Marking
 µF
microfarads
 nF
nanofarads
 pF
picofarads
1RO
 0.000001
 0.001
 1
100
 0.00001
 0.01
 10
101
 0.0001
 0.1
 100
102
 0.001
 1
 1,000
103
 0.01
 10
 10,000
104
 0.1
 100
 100,000
105
 1
 1,000
 1,000,000
106
 10
 10,000
 10,000,000
107
 100
 100000
 100,000,000


CAPACITOR TOLERANCE TABLE
C
 +/- 0.25pF
D
 +/- 0.5pF
F
 1%
G
 2%
J
 5%
K
 10%
M
 20%
Z
 +80 -20%

Examples:
103K = 0.01uF i.e 10nF  with 10% Tolerance
104K = 0.1uF i.e. 100nF  with 10% Tolerance
POLYESTER CAPACITORS WITH COLOUR CODES:

It is quite unusual to find capacitors with colour codes as they are no longer manufactured, but they will still be found in older equipment and parts boxes. Sometimes you may run across such polyester caps which will be marked with coloured stripes rather than numbers.  Three examples of these polyester capacitors with colour codes can be seen in the photograph below (Right hand side second row down).

Below is the colour code for some of these capacitors and gives the value in PICOFARADS (pF).  

FIRST DIGIT (pF)
First Colour
 SECOND DIGIT (pF)
Second Colour
 MULTIPLIER
Third Colour
 TOLERANCE
Fourth Colour
BLACK
 0
0
x 1
20 percent
BROWN
 1
1
x 10

RED
 2
2
x 100

ORANGE
 3
3
x 1000

YELLOW
 4
4
x 10,000

GREEN
 5
5
x 100,000
5 percent
BLUE
 6
6
x 1,000,000

VIOLET
 7
7
x 10,000,000

GREY
 8
8
x 100,000,000

WHITE
 9
9
x  1,000,000,000
10 percent

The Fifth Colour Band Is The Voltage Rating:

Brown
100 Volts
Red
250 Volts
Yellow
400 Volts


The table for polyester capacitors works in pretty much the same way as for resistors. 

Look at the photo below and reading from the top of the capacitor the colours are:
Yellow = 4   Violet = 7   Orange = Multiply by 1000    Black = 20 % Tolorance  Red = 250 Volts

This capacitor therefore has a value of 47,000 pF  (i.e. 0.047µF) +/- 20% at 250V

It must be remembered that unlike resistors there is no space between the coloured bands so if, for example, you have 22,000 pF capacitor of this type there will not be two separate thin red stripes but one thick red stripe.




POLYSTYRENE CAPACITORS:

These are quite rare and often look like silvery plastic cans with a wire at each end, and being made of polystyrene are easily damaged by heat, so care is needed when soldering with the use of a heatsink clip. Polystyrene capacitors generally have the value in pF (e.g. 470p) or nF (e.g 4.7n) and may have a letter to indicate the tolerance as per the table above (e.g. J - i.e. 5%) printed on the body and so are quite easy to identify.


The photo below shows some examples of capacitors both variable trimmers, fixed electrolytics, ceramic disc, polyester, tantalum bead and polystyrene types. The polystyrene capacitors are shown on the bottom left hand side with the silvery plastic cans - they are quite rare today and the polystyrene is easily melted so great care needs to be taken when soldering.






More on voltage markings.
Although this information is not entirely confirmed, some capacitors may have voltage
indicated by a letter, as in the table below:  (But this table is unconfirmed information!)
D = 16 volts
 Q = 500 volts
 U =  4000 volts
F =  25 volts
 R = 1000 volts
 W = 5000 volts
H = 50 volts
 S = 2000 volts
 X = 6000 volts
K = 100 volts
 T = 3000 volts
 Y = 7500 volts







LIGHT EMITTING DIODES
.
LED
LED's are useful devices but need to be treated with a little care, connected the right way round and usually need a series resistor which can be calculated using a fairly simple formula. So I here is the basic information you'll need. 		LED


.
LED
 The symbol used for an LED in circuit diagrams (schematic diagrams) is shown below:

Light Emitting Diode (LED) symbol

The photographs to the left and right show the physical appearance of LED's.
Orientation:

LED's must be connected into circuits with the correct orientation otherwise they will not work, or will be damaged. The anode is the positive (+ve) side of the device and this will be indicated by the longer lead. The shorter leg will be the cathode, which is the negative (-ve) side of the device. The cathode is, additionally, indicated by a 'flat' on the side of the component's body.


Voltage:
LED
LED
Light Emitting Diodes are generally low voltage devices and must not be connected to directly into a circuit. If they are they will almost certainly be destroyed. LED's have to be connected into circuits in series with a resistor in order to reduce the current flowing through the device to a safe level.


Calculating The Current Limiting Resistor:

The series resistor can be calculated using a simple formula, but the technical specifications of the LED concerned ideally need be known beforehand.
The Formula:  R = (Vs - Vf) / If

Where:
R is the resistor value
Vs is the supply voltage
Vf is the forward voltage drop across the LED (refer to LED data sheet)
If is the forward current through the LED (refer to LED data sheet)
LED
LED







LED

 E.G. If the LED specified has an If of of 20mA (0.02 amps) and a Vf of 2.5 volts and is to work in a circuit operating at 12 volts, the calculation would be:

R = (12 - 2.5) / 0.02 so R = 475 Ohms, or the next higher standard value.

In practice I usually find that with most common and typical LED's that a 1.2K or 2.2K Ohm resistor in 12 volt circuits is a good default value.
AC Operation:

For AC operation a diode such as a IN4148 is placed in inverse parallel with the LED and a resistor of half the value calculated from the above formula would be used.



Some Typical LED Specifications:

The table contains the figures necessary for calculating the value of the series resistor for some typical LED types. If possible, however, always consult the data provided by your LED's supplier or manufacturer for the most accurate specifications.
LED Maximum Forward Current
If		 Typical Forward Voltage
Vf		 Maximum Forward Voltage
Vf		 Maximum Reverse Voltage Vr
Standard Red 30 mA 1.7 V 2.1 V 5.0 V
Standard Green 25 mA 2.2 V
 2.5 V 5.0 V
Standard Yellow 30 mA 2.1 V
 2.5 V 5.0 V
Bright Red 25 - 30 mA 2.0 V 2.5 V 5.0 V
Low Current Types 30 mA 1.7 V 2.0 V 5.0 V
Super Bright 30 mA 1.85 V 2.5 V 5.0 V
High Intensity 30 mA 4.5 V 5.5 V 5.0 V

Take the usual care when soldering LED'sinto a circuit, although they are generally quite hardy it is possible to damage them with excessive heat.

N.B. It is worth noting that there are some high voltage LED's available that have the necessary resistor built in to the body and these may be connected directly ino 12 volt circuits.
LED







LED


OHMS LAW
.

OHMS LAW:

The Ohm is the Si unit of electrical resistance. It is equal to that of a conductor in which a current of one amp is produced by a potential of one volt.

Ohms Law:   V= I x R       I = V ÷ R      R = V ÷ I

This can be more easily remembered by using the V I R Triangle:

Ohms Law VIR Triange



POWER (Watts):

 Where:  P = Watts    V =Volts    I = Current in Amps

P = V x I          V = P ÷ I          I = P ÷ V

P = I² x R          P = V² ÷ R


The RMS value of V & I must be used in circuits using alternating current:
For AC circuits containing non-resistive components P = V x I x PF

Where PF = Power Factor.
Power Factor is P ÷ S

P = real power, measured in Watts
S = apparent power measured in volt-amperes (VA) 
.

I hope this page has helped out a little!
Please let me know!
Having difficulty in finding components?  I have added some ideas for component sources here >
Including some ideas for sourcing Older Vintage Components

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