Page 182 -

243_MasterPieces_04a.qxd 4/18/03 7:05 PM Page 154

154 Masterpiece 4 • PneumADDic II

NOTE
An actuator is a mechanism that can drive itself or other things to move.

PneumADDic II combines MINDSTORMS electric motors with pneumatic pumps
to create a compressor that provides the compressed air which drives the pneumatic
adding circuit.Another interesting facet of PneumADDic II is that it combines motors
with pneumatic switches so it can control the values provided to the pneumatic adding
circuit, and uses pneumatic pistons combined with MINDSTORMS touch sensors, so the
RCX can tell when there is enough pressure to perform an addition operation, as well as
determine the result of the addition process. If that was not enough, PneumADDic II also
combines pneumatic pistons with pneumatic switches to create the computing elements
of the pneumatic adding circuit. Finally, a calculator is useless without an interface for
inserting numbers therefore PneumADDic II combines eight MINDSTORMS touch
sensors into a 16-key keyboard.
As you can tell from the name, PneumADDic II is not my first attempt at a LEGO
pneumatic adding machine. My first adder, aptly named PneumaADDic, was also a success.
It could perform pneumatic addition, but was very slow, because the pneumatic adding cir-
cuit required a significant amount of pressure to operate correctly. It took a long time for
the pneumatic pumps, powered by MINDSTORMS electric motors, to generate enough
pressure to perform the functions I was looking for.This was compounded by the fact that
the computing devices (called gates) in the adding circuit for PneumADDic were more
mechanically complicated than they needed to be.This created a lot of friction, which in
turn forced PneumADDic to run at an excessively high level of pressure. PneumADDic
also needed a great number of parts to build only one pneumatic gate, and I only had parts
for three. Despite its weaknesses, PneumADDic was the first of its kind and was nominated
into the LEGO MINDSTORMS Hall of Fame contest.
PneumADDic II incorporates a simplified gate design, and utilizes a total of seven
gates in the pneumatic adding circuit. But, before we dive into the actual building
instructions for PneumADDic II, we should take a closer look at both pneumatics and
digital computing, as these are the two disciplines that lie at the heart of this machine’s
abilities.

Pneumatics

As previously mentioned, pneumatic devices work by harnessing the power of com-
pressed air.There are many examples of pneumatic devices in real life. Carpenters often
use pneumatic nail guns when building or roofing houses, and pneumatic devices are
commonly used in automated factories for bending and shaping metals. Hydraulics, a
technology similar to pneumatics that uses pressurized fluid instead of compressed air, is