Page 125 - Making things move_ DIY mechanisms for inventors, hobbyists, and artists

Chapter 5 Mechanical and Electrical Power, Work, and Energy 105

You can also generate your own power with a wind turbine or by pedaling a bike.
We’ll talk about how much power to expect from these alternative energy sources
later in the chapter.

Prototyping Power: The Variable Benchtop Supply

A variable benchtop power supply (see
Figure 5-5) is ideal for prototyping—the FIGURE 5-5 A variable benchtop power
supply (image used with permission from
initial phase of working out an idea.
SparkFun Electronics)
SparkFun’s (www.sparkfun.com/) TOL-09292
is one example, and Marlin P. Jones &
Associates (www.mpja.com) also has a good
selection.
These power supplies are plugged into a wall
outlet and act as power converters from AC
to DC. They are expensive and large—hence
the name benchtop supply. However, they
are ideal because you will undoubtedly work
with components that need different
amounts of power: some motors want 3V,
others want 24V, some want low or high
current, and so on.

CAUTION Be careful with these things. They can source a lot of power.

These types of power supplies allow you to vary voltage and supply the required
current while you are testing your project. A typical supply ranges from 0V to 30V and
0A to 3A. This flexibility can be a huge time-saver, so you may want to start here,
even if you plan to go mobile for the final product. Once you get all the power
questions ironed out in the testing and prototyping phase, you can choose batteries
or a fixed power supply and be on your way.

Look for benchtop power supplies that are regulated. These ensure that the voltage
1
won’t drop as current increases. This is important and will save you a lot of frustration.
You’ll also see supplies listed as switching or linear. The switching type supply is more
efficient, so usually more expensive, but worth it if you have the option.