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132 CHAPTER FOUR
LASERS AND LIGHT SAFETY
Radiation, at any frequency, can damage humans. The government regulates the power
that lasers can emit so it is “eye safe.” Although most small pointer lasers are eye safe,
it’s still not a good idea to employ such radiation. Be very careful about the amount of
light and laser light that the robot will emit.

FIRE AND ELECTROCUTION
UL and other companies we’ve discussed publish testing and design guidelines that
should be followed.

Environmental Considerations

In the design of a robot, we must pay attention to a number of environmental consider-
ations. Several factors in the robot’s environment will be critical to its reliability and
performance. Other factors are a bit less important. Among the factors to consider are
temperature, vibration, vandalism and theft, humidity, altitude, and contaminants.

TEMPERATURE

Most electrical systems and appliances are designed to work in an office environment
near 25 degrees centigrade (25C). Commercial-grade electronics are designed to work
from freezing to hot (0C to 70C). Most off-the-shelf systems have temperature specifi-
cations in this range. Industrial systems, designed to be a bit more robust, have a tem-
perature range of -40C to 85C. Military systems often have temperature specifications
of -55C to 125C. Separate temperature ranges are quoted for storage and for operation.
The worst-case temperatures often occur in vehicle applications, especially the very
high temperatures that can occur in car trunks.
In the design of the robot, study the temperature limitations of all the components.
Often the battery and displays will be the least robust parts, with a limited temperature
range. It is possible to violate temperature specifications, but it would be taking
chances; the system might fail. It is also possible to test the completed system at high
and low temperatures to help ensure that it will be able to handle temperature extremes.
If a system is exercised for about 4 days at its high temperature limit, it’s roughly com-
parable to 30 days of aging in the field.
Most semiconductors and other parts have what is called a bathtub curve for relia-
bility. Most of the failures occur during the first few months (infantile failures) and the