RESISTOR GUIDE
RESISTORS ARE COMPONENTS SPECIALLY DESIGNED TO ADD RESISTANCE TO AN ELECTRICAL CIRCUIT IN ORDER TO REDUCE THE AMOUNT OF CURRENT PASSING THROUGH THE CIRCUIT. YOU’LL USE THEM AT VARIOUS POINTS IN THIS BOOK FOR A VARIETY OF TASKS, FROM ENSURING A SAFE CURRENT FOR AN LED TO CREATING A VOLTAGE DIVIDER CIRCUIT.
The exact resistance value of a resistor is measured in ohms (Ω). If you don’t already know the value of your resistor, you can determine it using its colored bands. This table shows which value correlates to each color.
NOTE
If you’re color-blind like me, determining a resistor’s value from its colored bands is almost impossible. I’d recommend keeping your resistors in organized and labeled bags so you can quickly and easily identify their value. If you’re faced with an unknown resistor, you can use the resistance setting on your multimeter, to help you. Simply connect the two probes of your multimeter to either side of your resistor, and it will display its exact resistance.
COLOR |
FIRST BAND |
SECOND BAND |
THIRD BAND |
MULTIPLIER |
TOLERANCE |
Black |
0 |
0 |
0 |
1 Ω |
|
Brown |
1 |
1 |
1 |
10 Ω |
+/–1% |
Red |
2 |
2 |
2 |
100 Ω |
+/–2% |
Orange |
3 |
3 |
3 |
1 KΩ |
|
Yellow |
4 |
4 |
4 |
10 KΩ |
|
Green |
5 |
5 |
5 |
100 KΩ |
+/–0.5% |
Blue |
6 |
6 |
6 |
1 MΩ |
+/–0.25% |
Violet |
7 |
7 |
7 |
10 MΩ |
+/–0.10% |
Gray |
8 |
8 |
8 |
|
+/–0.05% |
White |
9 |
9 |
9 |
|
|
Gold |
|
|
|
0.1 Ω |
+/–5% |
Silver |
|
|
|
0.01 Ω |
+/–10% |
A standard resistor has four colored bands. The first two bands represent the first two digits of the resistor’s value. The third band is a multiplier that represents the number of zeros after the first two digits. The fourth band is the tolerance of the resistance; unless you’re doing specialized and precise work, you most likely won’t need to worry about the final band.
As an example, let’s work out the value of the resistor shown in Figure C-1.
FIGURE C-1 A four-band resistor
The first band is green, so its value is 5. The second band is blue, so its value is 6. The third band is yellow, which corresponds to four 0s. The fourth band is gold, meaning the tolerance is +/–5 percent.
The resistance value of this resistor is therefore 56 × 10,000 = 56,000 Ω, or 56 kΩ.
And that’s all there is to working out a resistor’s value from its colored bands!