Page 181 - Build Your Own Combat Robot

Build Your Own Combat Robot
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Each of the two joysticks controls two channels—one channel with the hori-
zontal direction, and one with the vertical. The top-of-the-line R/C sets, usually
intended for the R/C helicopter market, can have up to nine channels of servo con-
trol. Most of the high-end radio sets also have computerized control interfaces
that allow the driver to configure the channel allocation, and change mixing set-
tings, and the R/C system can be programmed for custom control sequences.
Whether you are independently controlling each of the channels that control
the left and right motors, or you are controlling the robot speed with one stick and
steering with the other stick, two channels are the minimum needed to drive a robot
in a controlled fashion. Some more-complex robots that involve omni-directional
wheels or multi-legged walking mechanisms need more than two channels for
drive control.
Most competitions require that weapons are controllable via remote control,
so you will need to include at least one channel for each weapon. Complex weap-
ons—such as saws on moveable arms or spring-loaded rams with separately con-
trolled release mechanisms—will need more than one channel. Gasoline engines
may require several control channels—one for the throttle, a second to start the
engine remotely, and a third to shut down the engine remotely. A general rule to
remember is that you will need a separate servo command channel for each action
that you want to control separately.

Radio Control Frequencies
The frequency bands for R/C systems are established by Federal Communica-
tions Commission (FCC) regulations. Specific bands of the radio spectrum are al-
located for use by R/C hobbyists, and radio manufacturers have standardized
specific frequencies inside these bands for use by hobby radios. Channel number
in a radio refers to a specific frequency within the allowed range of the frequency
band. The channel number should not be confused with the number of servo
channels the radio set can control. Frequency bandwidth allocation varies by
country; a radio operating on a legal frequency in the United States will not be legal
for use in the United Kingdom, and vice versa.

27-MHz Radio Frequency Band

The 27-MHz radio band is usually used for small R/C toy cars, planes, and tanks.
This frequency band crosses into the lower channels on the citizens band (CB) radio
frequencies, so there is a chance of interference by CB radio operators.
Both ground and aircraft vehicles are allowed to use the 27-MHz radio fre-
quency band, which is divided into six separate channels. The first channel operates
on 26.995 MHz, and each of the other channels are spaced every 0.05 MHz. Radio
sets for the 27-MHz band are available in both amplitude modulation (AM) and
frequency modulation (FM) configurations, and are usually low power and lim-
ited to two or three channels. Although they can be used for combat robots, this is