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PneumADDic II • Masterpiece 4 153

Introduction

This chapter describes PneumADDic II, my LEGO pneumatic adding/subtracting
machine. PneumADDic II combines a MINDSTORMS Robotics Invention System
RCX with motors, touch sensors, and LEGO TECHNIC pneumatic parts to make a
device that mechanically adds and subtracts series of numbers by using pressurized air to
manipulate a circuit.The fact that PneumADDic II performs these addition and subtrac-
tion functions mechanically, rather than digitally, is what really makes it unique.These days,
these types of functions can be performed digitally, almost instantaneously, by the simplest
of computers.The RCX itself can easily do so, as can any child’s calculator.Why then, you
might be asking yourself, would you build a machine that performed these functions
mechanically, when the RCX brick is capable of performing the same calculations digi-
tally? There are a couple of answers to that question.
When I first discovered LEGO pneumatics, I became very excited. My thought was
that I would be able to build complex moving devices that operated on only compressed
air. I’ve been a computer engineer for 20 years, and know quite a bit about designing
computer circuits. I assumed that I could use many of my computer design skills to create
complex never seen before LEGO pneumatic devices. I consulted JP Brown, a world-
renowned LEGO builder that I had met on the LEGO MINDSTORMS Web site, about
what I wanted to do. He told me that computer-like pneumatic circuits were not pos-
sible, due to the way the LEGO pneumatic switches work. I took this as a challenge and
set to work to prove that it was indeed possible.
A second answer to the question of why the idea of a LEGO pneumatic adding
machine appealed to me so much goes back even further into my past. When I was intro-
duced to digital electronics as a teenager, the first circuit that captured my attention was a
digital electronic adding circuit, similar to what you would find inside the RCX or a cal-
culator.The heart of PneumADDic II mechanical adding machine is a pneumatic adding
circuit that mimics the digital electronic circuit I first learned about 30 years ago.The fact
that my knowledge has come full circle in such a way is extremely fulfilling, especially
since I have been able to use LEGO parts to turn my theories and visions into reality.
LEGO TECHNIC pneumatic parts provide all the basics elements for building com-
plete pneumatic circuits.These include the following elements:

■ Pneumatic Pumps These pressurize air, which is the driving force behind all
pneumatic devices and circuitry.

■ Pressure Tanks These store the pressurized air for later use.

■ Pneumatic Switches These switches steer where the pressurized air goes.
■ Pneumatic Pistons These are used as actuators in LEGO designs.
■ Pneumatic Tubing and T-Connectors These elements connect all of the
other LEGO pneumatic components together.