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168 CHAPTER SEVEN
low-power technology as discussed previously, also has two other nice characteristics
we could use:
High noise margins Most semiconductor technologies, such as bipolar and
some FET technologies, have strict requirements for the voltage levels that can be
present on the circuit board. Processors and integrated circuits made from these
technologies have signals that only vary over a small percentage of the power sup-
ply voltage range. If the signals vary outside of these ranges, then logic errors
might occur and the robot will malfunction.
CMOS FET technology can tolerate a much wider range of signal voltages. With
some restrictions, CMOS logic gates regard signals above 50 percent of the power
supply voltage as logic one, and signals under 50 percent of the power supply volt-
age as logic zero. The power supply can even change voltage (within bounds) and
CMOS logic gates will still work just fine. It may be difficult to find off-the-shelf
computers built with just CMOS because the competing bipolar technologies have
the bulk of the commercial market, but certain manufacturers concentrate on
CMOS and other logic families cater to the requirements of portable and robot
applications. It should also be noted that some logic families work better than oth-
ers in the presence of nuclear radiation. If your robot will be going to truly hot
locations, give CMOS a good look!

Here are some PDF files that discuss high noise margin logic:
www.ece.pdx.edu/~greenwd/AN_375.pdf
http://lorien.die.upm.es/ macias/docencia/datasheets/info-familias/
hc-cmos-dc-characteristics.pdf
Power supply range CMOS technology will work over a relatively wide range
of power supply voltages. Most single board computers (SBCs) work off 5 volts,
but it’s not impossible to find boards that will accept a wider voltage range. Auto-
motive designers have been using CMOS and related chip technologies for years,
even though they are not stuck for energy.
Here are some sites providing information about CMOS logic families:
www.bychoice.com/cmos.htm
http://us.st.com/stonline/prodpres/standard/stanlogi/hcmos.htm
www.electronicstalk.com/news/sra/sra100.html

Power Regulation
Energy is not always available in a form that can be used successfully. Often, it has to
be transformed and tamed. This can be done in a few different ways and some are more