Datasheet

Chapter 2 • Shield, Lights, Servo Motors
62 • Robotics with the BOE Shield-Bot
The picture below shows the schematic of the circuit you create by plugging the servos into
ports 13 and 12 on the BOE Shield. Pay careful attention to wire color as you plug in the
cables: the black wire should be at the bottom, and the white one should be at the top.
 Connect your servos to your BOE Shield as shown in the diagram below. The left
servo connects to port 13 and the right servo connects to port 12.
 Make sure that you follow the cable colors shown in the figure, with the black
wire closer to the breadboard and the white wire closer to the board’s edge.
Connect the Battery Pack to the BOE Shield
To properly power the servos, you’ll need to switch to an external battery pack now. When
servos make sudden direction changes or push against resistance to rotation, they can draw
more current than a USB port is designed to supply. Also, it would be no fun for the BOE
Shield-Bot to be tethered to the computer forever! So, from here on out we’ll be using an
external battery pack with five 1.5 V AA batteries. This will supply your system with 7.5 V
and plenty of current for the voltage regulators and servos. From here forward, remember
two things:
1. ALWAYS unplug the battery pack when you are done experimenting for a
while. Even when the power switch on your BOE Shield is off (position-0), the
Arduino module will still draw power from the batteries.
2. Unplug the programming cable too, whenever you unplug the battery pack.
That way, you won’t accidentally try to run the servos off of USB power.
CAUTION: AC powered DC supplies are not recommended for the BOE Shield-Bot.
Some DC supplies provide much higher voltage than their rating. The BOE Shield-bot is designed
for use with a 7.2–7.5 V battery supply. It will work with higher supply voltages at low loads, but
the servo loads can heat up the regulator until it shuts off to protect itself.