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196 ROBOT POWER SYSTEMS

robot over. And it saves space for electronics and other parts. Avoid any location that requires
you to dismantle lots of parts of the robot just to access the batteries.

Wiring Batteries to Your Robot

There are lots and lots of ways to wire batteries to the rest of your robot. Picking the right
method depends on the design and complexity of your bot.
In all cases, it’s important to use a wiring system that eliminates the chance of short- circuiting
the terminals of the batteries. It’s also a good idea to use a connection scheme to prevent
damage if the battery pack is connected to the robot circuitry in reverse, as detailed in the
following section

Simple bots, replaceable cells. For the most basic robots, using battery holders with
individual cells, you can merely solder the battery pack to the electronics and motors.
To replace or recharge the batteries, just remove them from the holder.
Solderless breadboards. Rather than solder to the electronics, insert the wires from the
pack into the + and rails of the breadboard. You’ll need to solder a short (half- inch)
length of 22- gauge solid conductor wire to the end of the battery pack leads, so you can
plug into the breadboard.
Rechargeable packs with a standard 0.100″ two- prong female plug. Use correspond-
ing male header pins on your circuit or breadboard so you can readily connect and dis-
connect the batteries. Danger! This poses a chance of reverse polarity, so consider one
of the solutions under “Preventing Reverse Battery Polarity” (later in this chapter).
Battery packs with a polarized plug. Use the corresponding socket on your circuit board
or breadboard. A popular polarized connector found on DC wall transformers (see Fig-
ure 19- 6) is the coaxial barrel plug, discussed in the next section. It can also be used on
battery holders; use a six- cell (7.2- or 9- volt) holder and a 2.1mm barrel plug to power
an Arduino board with batteries.
Battery packs with a customized polarized plug. You can make your own polarized
connector systems or adapt one from the battery packs used in R/C model airplanes
and cars. These are also discussed in the next section.

Figure 19- 6 Wall transformer with a
barrel plug. If purchasing a wall transformer
for your robotics projects, make sure it
provides the correct voltage and that the plug
has the proper polarity to match your
components.

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