Page 305 - Robots Androids and Animatrons : 12 Incredible Projects You Can Build

construction of the robotic arm. While the gearbox increases the
motor’s torque, the robotic arm is not capable of lifting or moving a
great amount of weight. The maximum recommended lifting capac-
ity is 4.6 ounces (oz) [130 grams (g)].
The robotic arm kit components have been thoughtfully laid out for
kit builders (see Fig. 15.2). If you carefully follow the directions in
the robotic arm construction booklet, construction will proceed
smoothly. To help you, some of the assembly work is already com-
pleted. For instance, the five DC motors come with the gearboxes
already assembled and connected to the DC motors (see Fig. 15.3).
This helps move the construction along. In a few hours, you have an
operational robotic arm.
Basic motor control

To understand the basic function of wire control, let’s see how
digital signals can control a single DC motor. Controlling a DC mo-
tor requires two complementary transistors. One transistor is a
PNP type and the other is an NPN type. Each transistor functions
like a switch, controlling the current to the DC motor. The cur-
rent direction controlled by each transistor is opposite to that of
the other transistor. The direction of the current controls the di-
284 rection the motor spins, CW or CCW. Figure 15.4 is a test circuit
that you may build before building the robotic arm interface. No-
tice that if both transistors are turned off, the motor is off. Only

15.2 Robotic arm kit
Team LRN
Chapter fifteen