Introduction
Resistors are one of the most fundamental components used in electronics and electrical circuits. To easily identify resistor values, a color coding system is commonly used to mark the resistance on the body of the resistor.
Learning how to read these color codes is an essential skill for anyone working with electronics. In this comprehensive guide, we will cover:
- What resistance and resistors are
- Resistor color code systems
- 3 band
- 4 band
- 5 band
- Decoding color bands to read resistance value
- Calculating resistance from color codes
- Determining tolerance from color code
- Identifying special values like EIA
- Practical examples and exercises
- Common mistakes to avoid
- Other resistor markings
- Frequently asked questions
After reading this tutorial, you will be able to easily decipher the color codes to determine the resistance value of any common resistor. Let’s jump in!
What is Resistance and What are Resistors?
To understand resistor color codes, we first need to understand what resistance means and what resistors are.
Resistance is the property of a material that opposes the flow of electric current. It is measured in ohms and represented by the Greek symbol Ω.
Resistors are electrical components explicitly designed to provide resistance in a circuit. Some key properties of resistors:
- Made of resistive materials like carbon, wire windings, metal oxides
- Designed with a certain resistance value
- Used to limit current flow, divide voltages, damp signals, and more
- Available in many form factors like axial, SMD chip, rectangular, etc.
By adding resistors into circuits, we can finely control voltages and currents as needed. But to utilize them properly, we need to know their resistance values. This is where resistor color coding comes in.
Resistor Color Code Systems
There are a few standards for marking resistance values on resistors with colored bands. Let’s look at the common systems.
3 Band Color Code
This system uses three colored bands to denote the resistance as follows:<img src=”https://imgur.com/BEnfSfR.png” width=”200″>
- 1st and 2nd band – Digits for resistance value
- 3rd band – Multiplier
- (Optional 4th band – Tolerance)
For example, green-blue-red equates to a 56 x 100 = 5600 Ω resistor. Very simple and common coding.
4 Band Color Code
This expands the 3 band code by adding a 4th tolerance band:<img src=”https://imgur.com/gBrjaXR.png” width=”200″>
- 1st band – 1st digit
- 2nd band – 2nd digit
- 3rd band – Decimal multiplier
- 4th band – Tolerance
So yellow-violet-red-gold decodes to 47 x 100 = 4700 Ω with 5% tolerance.
5 Band Color Code
This further expands the code with an extra significant figure digit:<img src=”https://imgur.com/Tbye4Wf.png” width=”250″>
- 1st and 2nd band – 1st and 2nd digit
- 3rd band – 3rd digit
- 4th band – Multiplier
- 5th band – Tolerance
For example, brown-black-orange-red-gold equates to 10,000 x 100 = 1,000,000 Ω ± 5% tolerance.
This allows expressing higher resistances with greater precision.
Decoding the Color Bands
Each color in the sequence maps to a numeric digit or meaning as follows:
Significant Figure Bands
| Color | Digit |
|---|---|
| Black | 0 |
| Brown | 1 |
| Red | 2 |
| Orange | 3 |
| Yellow | 4 |
| Green | 5 |
| Blue | 6 |
| Violet | 7 |
| Grey | 8 |
| White | 9 |
Use the band colors to look up the digit values
Multiplier Band
| Color | Multiplier |
|---|---|
| Black | 1 |
| Brown | 10 |
| Red | 100 |
| Orange | 1,000 |
| Yellow | 10,000 |
| Green | 100,000 |
| Blue | 1,000,000 |
| Violet | 10,000,000 |
| Grey | 100,000,000 |
| White | 1,000,000,000 |
| Gold | 0.1 |
| Silver | 0.01 |
The multiplier scales the significant figure value
Tolerance Bands
| Color | Tolerance |
|---|---|
| Brown | 1% |
| Red | 2% |
| Green | 0.5% |
| Blue | 0.25% |
| Violet | 0.1% |
| Grey | 0.05% |
| Gold | 5% |
| Silver | 10% |
| None | 20% |
The tolerance indicates the acceptable resistance error
With these tables, you can find the digit, multiplier, and tolerance for any color band.
Let’s look at some examples decoding 3, 4, and 5 band resistors step-by-step:
Resistance Calculation Examples
3 Band Resistor
<img src=”https://i.imgur.com/BEnfSfR.png” width=”200″>
- Orange – 3
- Orange – 3
- Red – x100
3,3 x 100 = 330 Ω
Simple as that!
4 Band Resistor
<img src=”https://imgur.com/gBrjaXR.png” width=”200″>
- Yellow – 4
- Violet – 7
- Red – x100
- Gold – ±5% tolerance
4,7 x 100 = 470 Ω ± 5%
5 Band Resistor
<img src=”https://imgur.com/Tbye4Wf.png” width=”250″>
- Brown – 1
- Black – 0
- Orange – 3
- Red – x100
- Gold – ±5% tolerance
1,0,3 x 100 = 1,030 Ω ± 5% tolerance
This method can be used to read any 3, 4, or 5 band through simple digit look-up and multiplication.
Determining Tolerance
The color of the tolerance band indicates the precision of the marked resistance value. Common tolerances include:
- Brown – ±1%
- Red – ±2%
- Gold – ±5%
- Silver – ±10%
- None – ±20%
Higher precision resistors have tighter tolerances printed on them. For example, a gold band means the actual resistance should be within ±5% of the marked value.
So a 100 Ω ± 5% resistor can have an actual resistance between 95 to 105 Ω. Tolerance gives the acceptable margin of error.
Identifying EIA Values
There is also a special variant of 4-band color codes for EIA preferred values. It is denoted by:
- 1st and 2nd bands – Standard codes
- 3rd band – Decimal multiplier
- 4th band – Gold or silver ±5% tolerance
Gold as 4th band = EIA value x 0.1
Silver as 4th band = EIA value x 0.01
For example:<img src=”https://imgur.com/N5MWUqf.png” width=”200″>
Red-Red-Gold = 22 x 0.1 = 2.2 Ω
Brown-Black-Silver = 10 x 0.01 = 0.1 Ω
Both are standard EIA values. This code helps identify them.
Practice Exercises
Let’s practice decoding some example resistor color codes:
- Orange-Orange-Red
- Brown-Green-Brown-Silver
- Red-Violet-Yellow-Gold
- Blue-Grey-Black-Brown
- Green-Brown-Orange-None
Scroll down to check your work!
Solutions:
- 33 x 100 = 3300 Ω
- 15 x 10 = 150 Ω ± 10% tolerance
- 27 x 10,000 = 270,000 Ω ± 5% tolerance
- 68 x 1 = 68 Ω ± 1% tolerance
- 58 x 1000 = 58,000 Ω ± 20% tolerance
How did you do? With practice, you will be able to read resistor codes effortlessly.
Common Mistakes
Here are some common mistakes to avoid when decoding resistor color codes:
- Forgetting the multiplier – Make sure to apply the multiplier band or else your value will be way off.
- Mixing up tolerance and multiplier – It’s easy to flip these two adjacent bands by accident. Double check their order.
- Misreading similar colors – Red/orange or blue/violet can look alike on small resistors. Take care!
- Assuming wrong # of bands – Always confirm the band count before reading the resistor.
- Decoding non-standard codes – Some resistors use custom codes. Verify it is a standard scheme.
- Faded colors – If bands fade to almost white, they may be indistinguishable.
With experience, you will learn to avoid these pitfalls. When in doubt, check the datasheet or use a multimeter to measure the actual resistance.
Other Resistor Markings
While color coding is the most common, resistors may also be marked in other ways:
- Multiplier written numerically such as 10M or 10MΩ for 10 million ohms
- Tolerance written out like ±5% rather than color band
- 3 or 4 digit codes starting with the multiplier e.g. 471 = 470Ω
- Actual resistance printed numerically e.g. 10k
- SMD resistors marked with just a number string
So you may encounter alternate formats beyond the standard color codes. With practice, you’ll learn to interpret all the common schemes.
Frequently Asked Questions
Here are some common questions about resistor color codes:
Q: Why are colors used instead of just printing the resistance value?
A: The color bands allow cheap, permanent, and unambiguous marking without requiring printed text or symbols.
Q: What do more than 3 bands indicate on a resistor?
A: Additional bands denote tolerance and extra significant figure digits for higher precision.
Q: Why do resistors have a tolerance?
A: Due to manufacturing variations, the actual resistance cannot match the target value exactly. Tolerance specifies the allowable error range.
Q: What is the gold or silver multiplier on 4-band resistors?
A: These denote EIA preferred values. Gold = multiply by 0.1, silver by 0.01.
Q: Can you read a resistor’s value without decoding the color bands?
A: Yes, you can directly measure a resistor’s resistance using a multimeter if you need to confirm its value.
Conclusion
Understanding resistor color coding is indispensable for working with resistors in circuit design and analysis. This guide provided a comprehensive overview of decoding color bands including:
- Resistor coding systems – 3, 4, and 5 band
- Looking up digit values, multipliers, and tolerance
- Calculating resistance from color codes
- Identifying EIA values
- Avoiding common mistakes
- Handling non-standard markings
With this knowledge, you can now easily decipher resistor color codes and determine resistance values. Receiving a handful of resistors is no longer an intimidating puzzle!
Practice reading a variety of example resistor color codes until it becomes second nature. Mastery of these fundamentals will give you confidence working with resistors and building circuits.
