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Cheat Sheet

Circuitbuilding Do-It-Yourself For Dummies

If you want to try your hand at building circuits or other electronics, make sure you keep the right tools on hand, know how to read resistor color codes and the value markings for capacitors, and understand the metric system of units and voltage conversions.

Circuitbuilding and Resistor Color Codes

Resistors are common passive electronic parts (meaning they don't need power to run) for circuitbuilding. Resistors control currents and voltages and they're manufactured in a variety of ways. Use this table to read resistor color codes for circuitbuilding:

Color Value Stripe Multiplier Stripe Tolerance Stripe
Black 0 times; 1 (100)
Brown 1 times; 10 (101) 1%
Red 2 times; 100 (102) 2%
Orange 3 times; 1000 (103)
Yellow 4 times; 10,000 (104)
Green 5 times; 100,000 (105) 0.5%
Blue 6 times; 1,000,000 (106) 0.25%
Violet 7 times; 10,000,000 (107) 0.1%
Gray 8 times; 100,000,000 (108) 0.05%
White 9 times; 1,000,000,000 (109)
Gold times; 0.1 5%
Silver times; 0.01 10%
No color 20%

How to Read Capacitor Value Markings

When you’re building circuits with capacitors, you’ll need to learn to read the value markings, which not only designate values but other parameters as well.

###L (Three numbers and a letter) Numbers 1 and 2 are value digits.
Number 3 is a multiplier: 0 = × 1, 1 = × 10, 2 = × 100, 3 = × 1000, 4 = × 10,000.
Letter denotes tolerance: J = 5%, K = 10%, L = 20%
##p or ##n Numbers 1 and 2 are value digits.
p denotes pF, n denotes nF.

Drill Sizes Commonly Used in Electronics

Building circuits and other electronics requires a small electric drill, cordless or not. Invest in a small bench-mount drill press if you're installing circuits in project boxes and cabinets so it looks good. This guide shows you drill sizes you'll need:

Size Number Diameter Next Largest Fractional Size Clears Screw Size For Self-Tapping Screw Size
11 0.191″ 13/64″ 10
19 0.166″ 11/64″ 8
21 0.159″ 11/64″ 10-32
25 0.149″ 5/32″ 10-24
28 0.140″ 9/64″ 6
29 0.136″ 9/64″ 8-32
33 0.113″ 1/8″ 4
36 0.106″ 7/64″ 6-32
43 0.089″ 3/32″ 4-40
44 0.086″ 3/32″ 2
50 0.070″ 5/64″ 2-56

Metric System Unit Prefixes

For building circuits or other electronics, a system of prefixes is used to make managing and reading metric easier. Use this chart to learn the metric prefix, its symbol, and the decimal value.

Prefix Symbol Multiplication Factor
tera- T 1012
giga- G 109
mega- M 106
kilo- k 103
centi- c 102
milli- m 103
micro- m 106
nano- n 109
pico- p 1012

Voltage Conversions

Here are some handy mathematical formulas to help you figure out what those waveforms mean, and how to convert them to other measurements, when you're measuring voltage in your batteries or other electronic devices.

Sine or square wave VPEAK-TO-PEAK = 2 × VPEAK
Sine wave VRMS = 0.707 × VPEAK, VPEAK = 1.414 × VRMS
Square wave VRMS = VPEAK
Power to decibels dB = 10 log10 (Power 1 / Power 2)
Voltage to decibels dB = 20 log10 (Voltage 1 / Voltage 2)
Decibels to power Power 1 = Power 2 × antilog10 (dB / 10)
Decibels to voltage Voltage 1 = Voltage 2 × antilog10 (dB / 20)
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