Resistors

1
Resistors

• Resistors can be either fixed or variable in
  value
• Fixed resistors come in a variety of different
  shapes, sizes and forms
• Axial lead resistors have the value of resistance
  printed on them or as a colour code
• Surface mount resistors have a numerical code
  indicating a value
• All resistors have a tolerance value

2
Resistors

• Variable resistors are called potentiometers
• There is a fixed value of resistance between two
  terminals
• The moving part of the potentiometer is called
  the wiper

3
Resistors

• Four band resistor colour code
• 1st band provides the first digit of the code
• 2nd band provides the second digit of the code
• 3rd band is the multiplier
• 4th band indicates the tolerance value

4
Resistors

• Resistor colour code calculation
• The first band red has a value of 2
• The second band purple has a value of 7
• The third band has a multiplier of x 10
• The last band indicates a tolerance value of
  /-5
• Resistance value is 270? /-5

2
7
x10
/-5
5
Resistors on PCB
Resistors (axial components with color bands
6
Resistor Color Code
http//www.educypedia.be/electronics/resistorcolor
code.gif
Note A resistor with a single black-band is a
zero ohm resistor
6
7
Resistor Color Code
PPM Part per million
http//www.oilfield.de/download/techtabs/electron/
ccode001.pdf
7
8
Resistor Color Code Online Tools
Color to Value (with Tolerance)
http//www.electronics-lab.com/articles/basics/re
sist/index.html?result350
Value with (Tolerance) to Color
http//www.ealnet.com/m-eal/resistor/resistor.htm
8
9
Standard Resistor Values
Electronic Industries Association (EIA) standard
E24 Standard E24 specifies resistors based on
5 tolerance (often resistor of this category has
2 tolerance now a days due to advancement of
manufacturing techniques)
Standard Resistor values
100 110 120 130 150 160 180 200
220 240 270 300 330 360 390 430
470 510 560 620 680 750 820 910
10M Ohms (Where M can be any integer,
positive or negative)
For other standards http//www.logwell.com/tech/c
omponents/resistor_values.html
10
Resistor with Different Power Ratings
Examples 2 Watts 1 Watt 1 Watt 0.5
Watt 0.25 Watt 0.25 Watt
The size indicates the power rating, NOT the
resistance value
11
Resistor Examples
Source Basic Electronics, Bernard Grob
Through-hole Resistors
SMT Components
http//www.wordiq.com/definition/Resistor
(Larger size often indicates higher power rating)
12
Variable Resistor Examples
13
Resistor Code
Ref http//www.lalena.com/audio/electronics/colo
r/

• SIL (Single In-Line) network
• The 4 and 7 are significant digits and the 3 is
  the decade, giving 47 x 1000 or 47 KW
• The letter after the numbers is the tolerance.
  The different representations are M20,
  K10, J5, G2, F1.
• Detail Spec http//www.vishay.com/docs/31509/csc.
  pdf

• SMD (Surface Mount Device)
• The 1 and 0 are significant digits and 3 is the
  decade, giving 10 x 1000 or 10 KW

• Direct Value
• Resistors with larger physical size are often
  printed the value directly on their body

14
Resistor Specifications
Value Ohms (W) Tolerance of Ohmic
value Safety Rating Power in Watt Shape
Axial (mostly) Technology Through-hole or
SMD (Surface Mount Device)
15
Resistor Symbol