Page 131 - Making things move_ DIY mechanisms for inventors, hobbyists, and artists

Chapter 5 Mechanical and Electrical Power, Work, and Energy 111

Although you need to plug these power supplies into the wall, they are small enough
to be pseudo-mobile. The CupCake CNC from MakerBot (www.makerbot.com) has
one of these in it, and you can still carry the whole thing to a party if you want to.

Power Converters
AC adaptors, AC-to-DC converters,
and DC power supplies are names for FIGURE 5-8 AC adaptor (image used with
permission from SparkFun Electronics)
the power cables that usually have
large black boxes (wall warts) at the
point they connect to the wall. You
probably have one to charge your cell
phone (see Figure 5-8). They take the
AC power from the wall and step it
down to a nonlethal DC power in a
range we can use. The scary high
voltage and current from the wall
stays inside the plastic lump and gets
dissipated by the heat, and we get
nice, smooth, usable DC power out
of the other end. 4

All Electronics usually has a large and affordable selection of these kinds of power
supplies. They typically range from 5V to 12V and come in a variety of current options,
from about 300mA to 3A. You can also find supplies with selectable voltage settings,
like TM03ADR4718 from Herbach and Rademan (www.herbach.com). You can plug
these into your solderless breadboard to power your circuits. If you don’t know how
to do this or what a solderless breadboard is yet, that’s perfectly okay. You’ll learn
about solderless breadboards in Chapter 6.

Alternative Energy Sources
One problem with generating energy is that you must either use it or store it immediately.
You don’t need to worry about that with batteries or power supplies you plug into the
wall. The power companies that feed our homes will just charge more money if we
use more electricity, and batteries supply power through a chemical reaction until they
are drained.