Hacking Electronics illustrated Diy Guide For Makers & Hobbyists - PDF DOWNLOAD

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HowTo-Color (8) / Hacking Electronics / Simon Monk / 236-3 / Chapter 2

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Hacking Electronics That’s enough about Ohm’s law for now, we will meet it again later. It is the single most useful thing you can know about electronics. In the next section, we will look at the only other truly essential math you will need—power.

What Is Power? Power is all about energy and time. So, in a way, it’s a bit like current. But, instead of being the amount of charge passing a point, it is the amount of energy transformed into heat per second when a current passes through something that resists the flow (like a resistor). Forget the river, it doesn’t really help much here. Restricting the flow of a current generates heat, and the amount of heat generated can be calculated as the voltage across a resistor times the current flowing through it. The units of power are the watt (W). You would write this in math as: P=I×V So, in our earlier example, we had 10V across a 100Ω resistor, so the current through the resistor was 100mA and will generate 0.1A × 10V, or 1 W of power. Given that the resistors that we have from the SparkFun kit are 250 mW (0.25 W). Our resistor will get hot and may eventually break. If you don’t know the current, but you do know the resistance, another useful formula for calculating the power is: P = V2 / R Or, power is voltage squared (times itself) divided by the resistance. So, for the example earlier: P = 10 × 10 / 100 = 1 W That’s reassuringly the same answer as we got before. Most components have a maximum power rating like this, so when selecting a resistor, transistor, diode, and so on, it is worth doing a quick check and multiplying the voltage across the component by the current that you expect to flow through it. Then, choose a component with a maximum power rating comfortably greater than the expected power. Power is the best measure of how much electricity is being used. It is the electrical energy being used per second, and unlike current it can be compared for devices operating from

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Index

15min
pages 290-305

Hardware and Miscellaneous

0
page 287

EAGLE PCB

0
pages 281-282

Introducing: The Oscilloscope

0
page 279

AC Voltage

1min
page 275

Resistance

1min
page 273

How to Use a Lab Power Supply

0
page 278

Summary

1min
page 271

How to Reuse a Cell Phone Power Adapter

1min
page 270

Desoldering

0
page 268

How to Check a Fuse

2min
pages 264-265

How to Test a Battery

0
page 266

Summary

1min
page 261

How to Make a Software VU Meter

0
page 259

You Will Need

1min
page 252

How to Make a 1-Watt Audio Amplifier

1min
page 251

How to Take Something Apart AND Put It Back Together Again

0
page 263

How to Make an FM Bug

1min
page 247

How to Use a Microphone Module

3min
pages 245-246

How to Sense Magnetic Fields

1min
page 237

Converting a Stereo Signal to Mono

1min
page 244

Software

1min
pages 235-236

How to Use an Accelerometer

1min
page 233

Soldering Audio Connectors

2min
pages 242-243

How to Measure Temperature

0
page 231

Software

1min
page 230

You Will Need

1min
page 225

Using a Gas Sensor with an Arduino

0
page 223

8 Hacking with Sensors

1min
pages 220-221

Summary

1min
pages 174-175

Breadboard

1min
page 222

How to Charlieplex LEDs

1min
page 169

How to Type Passwords Automatically

1min
page 172

How to Drive a Servo Motor with an Arduino

1min
page 166

You Will Need

0
page 156

How to Use a Alphanumeric LCD Shield with Arduino

0
page 163

How to Control a Relay from a Web Page

1min
page 155

Software

4min
pages 159-162

Construction

0
page 157

Software (Brightness

2min
page 151

How to Use Arduino Shields

1min
page 154

Software (Flashing

1min
page 150

How to Measure Voltage with an Arduino

1min
page 146

Trickle Charging with a Solar Panel

1min
page 130

6 Hacking Arduino

1min
page 132

Modifying the Blink Sketch

4min
pages 136-138

Testing a Solar Panel

1min
page 129

How to Use Solar Cells

2min
page 128

Trickle Charging

1min
page 127

Calculating How Long a Battery Will Last

1min
page 125

Controlling the Voltage from a Battery

1min
page 122

Simple Charging

2min
page 117

Hacking a Cell Phone Battery

2min
pages 120-121

How to Charge a LiPo Battery

1min
page 119

Charging Batteries (in General C ................................................. 88

1min
page 115

Summary

0
page 109

Design

0
page 107

Storing Charge in a Capacitor

1min
page 106

Troubleshooting

0
page 104

You Will Need

0
page 94

Construction

4min
pages 101-103

How to Power Large Numbers of LEDs

0
page 95

How to Measure the Forward Voltage of an LED

0
page 93

Construction

1min
page 92

Breadboard

1min
page 91

Design

1min
page 90

Common Transistors

1min
page 74

LEDs for Illumination

0
page 88

Trying It Out

0
page 85

Summary

0
pages 80-81

Construction

4min
pages 68-71

Breadboard

1min
page 67

What Is Power?

1min
page 55

Ohm’s Law

1min
page 54

You Will Need

1min
page 36

Where to Buy Things to Hack

2min
page 29

Soldering

1min
page 37

A Basic Toolkit

2min
pages 30-31

Capacitors

1min
page 49

Summary

0
page 45

Joining Wires

1min
page 38
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