20 things to do with a LogoChip

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                        The Gizmology Project Book
                         A Playful Introduction to Electronics




                                     Table of Contents
  Electronics for Everyone........................................................................... 2
  LogoChip: A new electronic construction kit ......................................... 4
    Sample Project: A LogoChip Bike Speedometer .................................... 7
  How does this fit into our overall research program? ......................... 11
    More Playful Invention .......................................................................... 14
    System, System, System ........................................................................ 14
    LogoChips in the Developing World ..................................................... 14
    Center for Arts and Invention Proposal ................................................. 15
  Getting it out into the world ................................................................... 15
    The Gizmology Project Book ................................................................ 15
    How is this different from other things it will be compared to? ........... 15
    Instructive Examples .............................................................................. 16
    Fast, Cheap, and Out of Control: Self-Replicating Hardware and
    Decentralized Distribution ..................................................................... 17
  Beyond “Beyond Black Boxes” .............................................................. 17
  Appendix: 20 Things to Do With a LogoChip ...................................... 19
  Appendix: An Outline for The Gizmology Project Book .................... 22




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                      The Gizmology Project Book
                      A Playful Introduction to Electronics1

                       Bakhtiar Mikhak and Brian Silverman
                Media Laboratory, Massachusetts Institute of Technology

                                     Robbie Berg
                        Department of Physics, Wellesley College



Eventually the art went out of radio tinkering. Children forgot the pleasures of opening
and eviscerating their parents’ old Kadettes and Clubs. Solid electronic blocks replaced
the radio set’s messy innards—so where once you could learn by tugging at soldered
wires and staring into the orange glow of the vacuum tubes, eventually nothing remained
but featureless ready-made chips, the old circuits compressed a thousandfold or more.
The transistor, a microscopic quirk of silicon, supplanted the reliably breakable tube,
and so the world lost a well-used path into science.

                               — James Gleick,
                               Genius: The Life and Science of Richard Feynman [1992]


Electronics for Everyone
A child growing up today is surrounded by ever more powerful and, in many ways, ever
more complicated and mysterious electronic gizmos and gadgets. In spite of the central
role that these devices often play in our lives, the inner workings of these ―black boxes‖
are almost completely hidden from view and are often poorly understood by their users.
Electronics is typically viewed as a formidable subject that is best tackled by expert
practitioners.2

Why is it that most people view the subject of electronics as inaccessible and esoteric?
Well, for starters, the electronic world is inherently a more abstract and less familiar one

1
  This document is intended an ―internal memo‖ whose purpose is to generate discussion
and feedback and help give focus to the LogoChip project. (Certain sections, such as the
one called ―How does this fit into our overall research program?‖ are explicitly intended
for an internal audience only.) But we hope that this memo will also serve as a starting
point for a book proposal, a grant proposal and / or a research journal article.
2
  Even among the ―technically minded‖, one finds a surprising amount of discomfort
with even relatively ―simple‖ electronics. For example it is striking how often in casual
conversation working scientists will volunteer that they feel under prepared in their
knowledge of electronics.


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than, say, the mechanical world. We interact with the mechanical world directly with our
senses, which has lead to a multitude of ways in everyday life for us to play with
mechanical ideas, building with blocks or taking apart a car engine for example. There
have never been many good opportunities for novices to play with electronics, but in
recent times the situation has gotten noticeably worse. The ever increasing complexity of
our electronic devices has served over time to diminish the depth of our experience with
the inner workings of the electronic world. In the days before the coming of solid state
electronics and integrated circuits, one could more easily look at a circuit and see how the
electron stream flowed. Over the decades the capabilities of our electronic technologies
may have progressed at incredibly rapid rates, but our access to good ways to for non-
experts to creatively play with electronic circuits and ideas has lagged far behind. For a
young Richard Feynman, the process of tinkering with a broken radio could serve as an
ideal playground for exploring electronics (and also act as a launching pad for making
connections to other scientific ideas). But for the present age of digital electronics, few
comparable experiences beckon.

The standard treatments of electronics in books or the curriculum are often too formal
and theoretical. Or they adopt the style of a cookbook, providing recipes for constructing
interesting electronic gadgets, but not aiming to provide a deep understanding of the
underlying principles. By only constructing circuits that have been designed by others,
readers miss an important opportunity to learn the art of debugging a flawed design. In
either case these approaches fail students along a critical dimension; they typically do not
bring most to the point where they are able or even want to design their own electronic
circuits or build their own electronic inventions.

In most of the standard introductory electronics experiences the devices being
constructed often do not have a particularly compelling use. Typical are ―bulbs and
batteries‖ exercises, in which students use a kit consisting of a few batteries, flashlight
bulbs and wires to build and explore simple dc circuits. While the underlying ideas that
are in play here (e.g. series vs. parallel circuits, Ohm’s Law, short circuits, etc.) may be
accessible at a fairly early age, it is hard to see how someone would be inspired to extend
this kind of activity into a long term project. The remarkable electronic gadgets that
surround us in the world today raise expectations to a very high level. Kids are bound to
be somewhat disappointed with an exercise that results simply in turning on a flashlight
bulb.

Introductory electronics books and kits usually adopt a bland style that appeals to a
narrow segment of geeky hobbyists. To see what the client base for these books and kits
looks like, just walk into your neighborhood Radio Shack and check out the customers,
particularly the group hovering in the electronic components section: The group tends to
be overwhelmingly male and the projects that are highlighted represent only a small
range of the possibilities. (One telltale symptom: Few if any craft materials appear in the
books.)

But this need not be so. With a more eclectic set of sample projects and a more
imaginative exposition there are many more people who would become fluent designers
and creators of electronic inventions. For example, there are many ways to make


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connections to the arts community by using electronics to create interactive art.

If the important and powerful ideas of electronics are to be more widely accessible, new
tools and new methods are needed. We envision an approach that is playful in spirit while
still seeking to engage learners in the deep underlying principles of electronics and the
broad connections of these ideas to other areas of engineering and science.


LogoChip: A new electronic construction kit
Paradoxically, the same microelectronic technologies that have contributed to the black-
boxing of modern electronic circuits can also be used as the basis for a new kind of
construction kit that will help reintroduce a vigorously creative and playful dimension
into the design of electronic inventions. The basic building block that we have developed
for this kit is an easily programmable and inexpensive embedded microcontroller called
the LogoChip. Users can develop programs using a special version of the Logo
programming language on a desktop or laptop computer and then download these
programs to the LogoChip. LogoChip Logo combines all the power and elegance of the
Logo programming language with the ability to directly configure and control the
individual pins on the LogoChip.

A schematic for the LogoChip hardware is shown in the figure below.




  Figure 1 – LogoChip Hardware. Pins shown in black can be configured by users as
     digital inputs or outputs. (―Port A‖ can also be configured as an analog inputs.)

The LogoChip is based on an inexpensive ($3) PIC microcontroller that has been



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programmed with a virtual machine implementation of Logo. A user would typically
construct the LogoChip hardware on an electronic breadboard by connecting the PIC to a
small number of external parts: a resonator that acts as a system clock, a button to start
and stop program execution, and a bi-color LED which serves as an indicator of the
machine’s current state. A cable connected between the LogoChip and the serial port of a
personal computer allows Logo programs composed on the PC to be downloaded onto
the LogoChip. Sixteen LogoChip pins (shown in black in figure 1) can be configured by
users as either digital inputs or outputs. Five of these pins can also be configured as
analog inputs.

The idea of providing a high level language interface to a microcontroller is certainly not
new. The popular Basic Stamp, for example, does exactly this. But there are important
syntactic and stylistic differences between the LogoChip environment and existing
environments like the Basic Stamp. Logo programs have a structure more like natural
language. Programs written in Basic tend to be less structured and hence less readable
and harder to follow than Logo programs. Another difference, admittedly more subjective
and harder to quantify, is that Logo programs have a style that tends to be ―softer‖ and
more playful than Basic programs. The LogoChip environment also features a command
line user interface, so that users can immediately test out the effects of modifications to
the program. The LogoChip hardware will also be significantly lower in cost (by a factor
of 5 or more) and therefore potentially accessible to a much wider audience than the
Basic Stamp. (See the section entitled Fast, Cheap, and Out of Control: Self-Replicating
Hardware, Decentralized Distribution below.)

But more important than differences in the style of the LogoChip technology are
differences in the style of the LogoChip projects that we plan to develop and encourage.
A LogoChip based construction kit provides a low threshold for novices to get started on
interesting projects. In these starter projects the emphasis is on small, simple and
understandable additions to the LogoChip; not on adding lots of specialized components
that hide a lot of their internal goings-on. For example one might start by plugging a
LogoChip directly into an electronic breadboard and connecting a light emitting diode
(LED) to pin B0 as shown:




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When current flows through a LED it lights up. (A diode is like a one way street; the
circuit must be arranged so that the current flows in the direction of the arrow.) Here is
what the Logo code that would make the LED flash once might look like:

       to light-on
       setbit 0 portb                                 ;makes pin 0 of portb
                                              +5V
       end

       to light-off
       clearbit 0 portb                       ;makes pin 0 of portb 0V
       end

       to flash
       light-on
       wait 1
       light-off
       end
Suppose we now connect a ―red/green‖ LED, between pins B0 and B1 of the LogoChip.
(The red/green LED is simply a red LED and a green LED located in close proximity in a
common housing and oriented in opposite directions,)




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We can make the LED turn red:

       to red
       setbit 0 portb
       clearbit 1 portb
       end

or green:

        to green
        clearbit 0 portb
        setbit 1 portb
        end
or, by rapidly switching between red and green states, we can make it appear yellow:


       loop [
                                                     red mwait 1
                                                     green mwait 1]
       end


       Sample Project: A LogoChip Bike Speedometer
It is easy to extend these simple elements into a variety of projects. For example by
wiring a collection of LEDs one could build programmable jewelry such as a mood ring,
or a novel kind of display to mount on a spinning bike wheel.

We envision that much of the circuit-building in these projects would be on electronic
breadboards of the type shown in the picture of the bike speedometer shown below.
There is a nice tactile, almost ―craft-like‖ element to this art. We are also thinking of
simple and inexpensive ways that would allow people to build more permanent circuits,
short of sending the boards out to a professional fabricator.


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The LogoChip shown in the figure is connected to seven tiny red LEDs, arranged in a
single column oriented parallel to the spokes of the wheel. The LogoChip can control
exactly when a particular light turns on or off. Also connected to the LogoChip is a
―magnet sensor‖, a magnetic switch that closes whenever it is near a magnet. This
enables the LogoChip to sense exactly when the sensor passes by a magnet that is
mounted on the inside of the bike frame.




A simple computer Logo program is running on the LogoChip. The program determines
the period for one revolution of the wheel by measuring the amount of time between
successive passes of the magnet sensor. Since the circumference of the bike wheel is
known, the speed of the wheel can easily be calculated.

The ―font‖ used in the speedometer is implemented on a grid that is seven rows high by 5


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columns wide. For example the pattern of lights used to display the numeral ―eight‖ is
shown below. To display this numeral using a single column of seven lights, the
LogoChip flashes five different combinations of the lights in rapid succession, each
combination corresponding to one of the five different columns that make up the desired
character. Each combination is lit for the same short time (corresponding to about 1% of
the period for one revolution of the wheel). Since the wheel is moving, the column of
lights has moved to a slightly different place each time a new combination flashes.
Because of the relatively long ―persistence‖ of human vision‖, a viewer will perceive a
two dimensional image of the character.




In order to give a sense of the LogoChip language, the Logo code used for the bike
speedometer is shown below.

       to speedometer
       loop [
          wait-for-magnet                   ; wait for the magnet sensor
                                            to pass by the magnet
           setT timer                       ; T is the time elapsed (in
                                            milliseconds) for one full
                                            revolution of the wheel
           resett                           ; resett the LogoChip’s
                                            internal timer to start
                                            timing the next revolution




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             setcolumn-time T / 100             ; column-time, the
                                           amount of time the column of
                                           LEDS remains lit, is set to
                                           1% of the time required for a
                                           full revolution. Note this
                                           simple method results in
                                           characters whose width does
                                           not vary as the speed of the
                                           wheel changes.
             display speed T               ; display the speed (in
                                           km/hr) that is calculated
                                           using the period T
             alloff                        ; turn of all the LEDs
             ]
       end

       to speed :n                         ; report the speed in units
                                           of km/hr
             output 8043 / :n              ; the speed is proportional
                                           to 1/T. Given that the wheel
                                           has a diameter on 27 inches,
                                           the speed in km/hr is 8043/T
       end

       to display :n                       ; display the desired numeral
       if :n = 0 [zero]
       if :n = 1 [one]
       ….
       if :n = 9 [nine]
       end

       ; the “font” must input, one numeral at a time

       to eight                            ; here, for example, is the
                                           pattern used for the numeral
                                           eight
       light-column      $6c
       light-column      $92
       light-column      $92
       light-column      $92
       light-column      $6c
       end

       …
       to light-column :n                  ; light up the desired
                                           pattern for the column of


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                                              LEDs and wait for the proper
                                              number of milliseconds.
       put portb :n
       mwait column-time
       end

       to alloff                              ; turn all the LEDs off
       put portb 0
       end

This bike speedometer has a whimsical yet practical nature. It strikes us as an example of
a project that leads very naturally o contact with a lot of important ideas. It also stands a
good chance of making a personal connection, at least to someone interested in bicycles.
And it suggests a wide number of ways it can be extended. For example it could be used
to make dynamic patterns. Or it could be incorporated into a ―build your own scientific
instrument‖ activity of the Brian’s Bike project type as well as other ―build your own
display (representation)‖ activities, such a ―build your own programmable jewelry‖.

The inspiration for the LogoChip bike speedometer came from a popular new kind of
clock that you may have seen in a store like Sharper Image or sitting on someone’s office
desk. The display for this clock consists of a column of LEDs that flick rapidly back and
forth on the end of a metronome-like mechanism. Like the LogoChip bike speedometer,
this gizmo can display two dimensional text and is often programmed to show the current
date and time. This is a gadget that immediately strikes many people as being cool and
intriguing (an obvious prerequisite for something that is offered for sale at a place like
Sharper Image). It might even inspire some viewers to reflect on how it works. But
viewers are not likely to think of it as the sort of thing that they could ever invent
themselves. Our goal is to change this perception.



See the appendix 20 Things To Do With a LogoChip for brief descriptions of more ideas
for LogoChip projects.


How does this fit into our overall research program?
A starting premise of the LogoChip project is of a type that is common to many of our
research projects: we think that electronics is an example of an ―advanced‖ domain that
can be made more accessible (and learned at an earlier age) with the appropriate tools.
The new tools we plan to develop are the LogoChip hardware and software and an
accompanying ―project book‖, whose working title is The Gizmology Project Book: A
Playful Introduction to Electronics. Some project ideas that would be appropriate this
book have their origins in projects and materials that were first developed as part other
projects such PIE and Beyond Black Boxes. Thus this book could serve as a means for
broadening the audience for these projects.

It is an open question as to exactly what the age range we would end up targeting with


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this book. Our feeling at this point is that The Gizmology Project Book would be aimed
mainly at high school and college ages. But we should, in the longer run, work on
developing LogoChip projects for kids as young as middle school age. (This would be in
the spirit of our earlier programmable brick work, which mostly started with older
students (e.g. 6.270) and ―filtered down‖ to younger kids over time.)

               Playing with circuits
Consider the popular example of the Play-Doh MIDI instrument. This provides a
wonderful opportunity way to play (both figuratively and also quite literally) with some
of the most important ideas in electronics. But when implemented with Crickets we fail
to take advantage of this opportunity.




The basic circuit, shown above, is an example of a voltage divider. The Cricket supplies 5
volt to a pair of resistors arranged in series. The first of this resistors is a fixed 33,000
ohm resistor that is on the Cricket circuit board. The second resistor consists the Play-
Doh that is pressed between two electrodes that are connected to the Cricket’s sensor
port. The sensor port of the Cricket is connected to an internal analog to digital converter
that measures the voltage across the Play-Doh and converts it to a number between 0 and
255. The key electronics idea here is that the 5 volts supplied by the Cricket is ―divided‖
between these two resistors. The value of the Play-Doh’s resistance, relative to the fixed
33,000 ohm resistance determines what fraction of the 5 volt change will occur across the
Play-Doh and hence what number the analog to digital converter will return. Since the
resistance of the Play-Doh turns out to depend on its shape, squeezing and stretching the
Play-Doh results in different sensor readings, which can be mapped by a Logo program
into different musical sounds.




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The voltage divider circuit is probably the most important circuit in all of electronics. (It
turns out that by making use of the so-called Thevenin theorem just about every circuit
can be thought of as a collection of connected voltage dividers.) It is striking how little
intuition most people (even college physics majors!) bring to this topic. And building a
Play-Doh MIDI instrument constructed with a Cricket and a MIDI bus device probably
doesn’t help much. It is hard to see (or even be aware of) the voltage divider circuit when
this project is built using a Cricket. On the other hand if this project were implemented
with a LogoChip the existence of the voltage divider circuit would be explicit, providing
a good opportunity to develop important intuitions.

               Going down a level
Here’s a caricature of the thoughts someone working on a Cricket-based Beyond Black
Boxes project might have:

       First Reaction: Aha! Now that I’ve built my own instrument I am beginning to get
       a sense of what’s going on inside all these other black boxes that surround me.

       Second Reaction: Uh-Oh. Wait a second. The Cricket is another black box that I
       don’t understand.

But if this person also has access to LogoChips a third reaction becomes possible:

       Aha! I can use a LogoChip to build my own custom Cricket.

What’s inside the black box? Like those nested Russian ―Matryoshka dolls‖ one always
finds a collection of other black boxes. But now one can begin to understand the
relationships and connections that exist amongst them. There is a great value in allowing



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users to ―go down at least one level below Crickets‖. Doing so demonstrates a kind of
―proof by induction‖ that, over time, progressively deeper understandings of how
something works are possible.


       More Playful Invention
Access to a versatile electronics construction kit (and an understanding of the underlying
principles of electronics that grows as a result of playing with such a kit) broadens the
range of possible inventions. We should see if any PIE participants would be interested in
trying to do LogoChip-based projects in a museum setting.


       System, System, System
LogoChip-based projects are a natural way to follow up, customize and extend other
programmable brick projects. There will often be a natural progression from Cricket-
based to LogoChip-based projects. We can think of Crickets and LogoChips as members
of a ―system‖ of programmable bricks, in much the way that the various LEGO products
form a system. Typically LEGO users progress from DUPLO to Basic to Technic. While
successive products become more ―advanced‖, they share a common vocabulary.
Expertise and comfort developed at one level become foundations for work at the next
level. Similarly The Cricket and LogoChip environments share a nearly identical
language, and, just as important, a common spirit.

With a LogoChip you can build their own ―custom Cricket‖. Customization allows you to
build devices which, like the classic Cricket, are cheap and small, with the additional
benefit that now you can include only those specialized features that are needed for a
particular project. Once you are willing to do a bit of electronics, this approach has some
distinct advantages compared to the alternative approach of using bus devices to provide
for specialized capabilities: The cost is lower and users are not dependent on a
specialized source of bus devices. Also, there are potentially fewer black boxes
encountered.

We don’t want to push too hard on this claim. The fact is that Crickets are not (yet) in
widespread use and the book that we plan to write will not assume that readers have
access to Crickets. Still it is valuable to demonstrate in a research setting the value having
an internally consistent system that appeals to a wide range of ages. And as the Playful
Invention Company comes on line, Crickets will become available to a wider audience.


       LogoChips in the Developing World
The low cost and decentralized distribution model for the LogoChip makes it a natural
candidate for projects in the developing world. The LogoChip is already playing an
important role in the project in Costa Rica. (More to be added here…)




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       Center for Arts and Invention Proposal
Interactive art projects based embedded microcontrollers such as the Basic Stamp have
been embraced by the arts community, who have used it to build some wonderfully
innovative interactive art. This embrace has, in our opinion, been in spite of the ―techy‖
feel of the Basic Stamp technology. The supporting written materials for the Basic Stamp
tend to read more like an instruction manual than a text aimed at conveying a deep
understanding of electronics or engineering principles.

There is an opportunity here to do much better. It is worth thinking about how the
LogoChip project might fit in with a proposal to form an NSF center focusing on
"learning through arts, design, and expression".


Getting it out into the world

       The Gizmology Project Book
The main way that we plan to disseminate this work is through publication of a relatively
short book, whose working title is:

       The Gizmology Project Book: A Playful Introduction to Electronics

As implied by this title, this will be a project centered book, written in an informal style.
But we would like to make it mostly ―self-contained‖ providing enough background
theory and explanation so that a novice could read the book and work on projects without
needing to extensively consult other references.


       How is this different from other things it will be compared to?
Here’s one way of framing for ourselves (no one else would understand all the
references):

       The Gizmology Project Book is to Horowitz and Hill’s The Art of Electronics as
       Wellesley’s Robotic Design Studio is to MIT’s 6.270 Robot Competition.

Robot contests from MIT’s 6.270 to cable television’s BattleBots have gained high
visibility and inspired many to become involved in creative engineering experiences.
While inspired by 6.270, Wellesley’s Robotic Design Studio represents an alternative
vision of how robot design can be used to teach engineering in a way that is more
inclusive and provides more room for artistic expression than contest-centered formats.

Similarly, the publication of Horowitz and Hill’s The Art of Electronics a generation ago
can be seen as an important milestone in the ―democratization‖ of the learning of
electronics. Whereas previously the design of electronic circuits was mainly the province
of the calculator-bound electrical engineer, the less formal, more intuitive style of The Art
of Electronics opened up the design of electronic circuits to a large new audience
consisting of a wide range of science students and professionals. With The Gizmology


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Project Book we aim to take this democratization a step further, aiming at an even
broader audience: For example, we will take the term ―art‖ more literally than Horowitz
and Hill. We want to enable our readers to use electronics as a means of expression.

     The Basic Stamp, by Parallax – As discussed above, it is not just a matter of Logo
    being better than BASIC (which it is). The difference here is more stylistic than
    technical.

     Robotic Explorations, by Fred Martin – His book is much more ―robot-centric‖
    than what we envision for The Gizmology Project Book. Also the electronics tends be
    remain mostly hidden.

     Mobile Robots, by Jones and Flynn – For all its merits this is often a catalogue of
    available materials and very specific ―how to‖ suggestions. We want to aim more at the
    underlying principles of electronics and the related big ideas of math, science, and
    engineering.


          Instructive Examples
Here are some existing books that contain some inspirational elements which can serve as
models for our book::

     Klutz Books - Perhaps we should think of The Gizmology Project Book as a Klutz
    Book for electronics. It could come with a packet of starter stuff; including a LogoChip.

      The Way Things Work. - While The Way Things Work playfully deconstructs
    inventions that were made by others, The Gizmology Project Book would serve as a
    guide to help readers playfully construct inventions that they make themselves. The
    illustrations in The Way Things Work are a great way to set a playful and informal tone.

     Radio Shack Project Books by Forrest Mims These are often good at emphasizing
    simple ―transparent‖ sensors and circuits. (e.g. touch sensors like the one in Katy’s bird
    feeder, a ―shadow detector,‖ moisture meter, water level detector, etc.) But these books
    are much more in the mode of a set of building plans rather than the intellectual
    exploration of important ideas that we would be aiming for.

    Other “projects books” such as The Starlogo Projects Book, the various
    Microworlds Projects Books

     The Student Manual for the Art of Electronics by Horowitz and Hayes. There’s
    much to like here, but it is more technical and less playful that what we will aim for.
    There is little opportunity for readers to design their own circuits. The book is also more
    than a decade old, which is an eternity in the world of electronics.




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       Fast, Cheap, and Out of Control: Self-Replicating Hardware and
       Decentralized Distribution
When you want to build something for your home you might go to a hardware store like
True Value or Home Depot and buy building materials and tools. It doesn’t much matter
which store you pick. Most building supplies are fairly generic in nature.

This is the kind of distribution model we will adopt for the LogoChip hardware. Unlike
the various programmable brick technologies (e.g. Crickets, Mindstorms RCX, Handy
Board, the Basic Stamp), which rely on a single centralized distributor, the LogoChip can
be obtained by ordering a garden variety PIC microcontroller from a catalog based
electronics parts vendor like Digi-Key and then transforming it into a LogoChip by
downloading through a serial connection the LogoChip firmware, which will be available
for free online. With this model, users should feel like they are working with a ―raw‖
building material, as opposed to a finished product that has already been constructed by
someone else.

Actually, if you started off with just a raw PIC microcontroller you would need to use a
$100 external ―PIC programmer‖ to load the LogoChip firmware. This sounds like a
costly complication. But once you have a single LogoChip in your possession it turns out
it is quite simple to use this LogoChip to build your own PIC programmer. Thus a
LogoChip becomes self-replicating. Friends can make LogoChips for friends. The one
LogoChip that will come with The Gizmology Project Book is plenty.

In a similar vein, an early LogoChip project might be to ―build your own electronic test
instruments‖. For example, suppose you build a new LogoChip and turn it for the first
time and find it doesn’t seem to work at all. One of the first things to check is to see if the
external ―clock‖ (oscillator) is running? You would typically do this by connecting an
oscilloscope directly to the clock pins on the LogoChip and looking to see the
oscillations. But oscilloscopes are expensive and you might not have one. Also, they. are
somewhat tricky for novices to learn to use. In some circumstances it might make more
sense to build your own specialized LogoChip-based device designed to tell if the clock
is running.

There are some big advantages of this kind of approach. The low cost and decentralized
distribution makes it much easier to provide access to LogoChip projects to people all
over the world. Moreover ,this approach fosters a sense of independence, self-reliance
and group ownership in the spirit of the free / open-source software movements.


Beyond “Beyond Black Boxes”
The LogoChip project is in many ways a natural follow on to the Beyond Black Boxes
project. In the BBB project, as in most of our programmable brick work to date, almost
all of the electronics has remained hidden inside the black boxes pre-built Crickets, bus
devices and sensors. While this is probably the right decision for the youngest learners, it
is worthwhile to ask whether we have been overly quick to hide the electrical circuits
from users. Is plugging wires into a breadboard and digital electronic or understanding


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and applying Ohm’s Law really more complicated or than building Mindstorms
creations? Perhaps we are biased because none of us grew up playing with LogoChips.




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Appendix: 20 Things to Do With a LogoChip
1. LogoLights – Connect LEDs to a LogoChip to make novel displays.

       Arrange LEDs in a column along the spokes of a bicycle wheel and use a magnet
       to sense the wheels rotation. Us the spinning LEDs to display the bike’s speed or
       to make a dynamic pattern, perhaps a one dimensional cellular automata.

       Make interactive jewelry that features dynamic patterns of light.

       Arrange the LEDs a circle and display information by varying the ―speed of
       rotation‖ around the circle or the size of a ―sector‖.

2. Smart Alarms (refrigerator, diary, burglar, bird feeder)

3. Clocks – Starter project make a stopwatch that uses a unique way to display the time.

4. Make Your Own Music – Start with a simple beep + square waves (perhaps making
use of the PIC’s built in pulse width modulation feature.) Improve the sound quality by
making your own sinusoidal wave tables. Improve sound further by modifying wave
tables to correspond to different instruments. Make your own MIDI instrument by
connecting a LogoChip to a commercial MIDI sound source. (It’s quite easy to do this.)
Make a Play-Doh synthesizer or an Ice Theramin.

5. Automatic pet feeders or a plant waterer

6. Braitenberg Creatures (hacking an existing toy such as bubble gun, LEGO Duplo
car)

7. Kinetic Sculpture / Interactive Art -

8. Make Your Own Meter

9. Make Your Own Strobe (edgerton.doc) – This can be made using the transistor
driven high brightness LEDs used in the bike speedometer. Use the strobe to look at a
vibrating guitar string. Use a microphone and a bit of computation to determine the sound
frequency and use this frequency to drive the strobe. Use the strobe to take high speed
photo of a bat hitting a ball.

10. Directional Sound - as in the Joe Paradiso Ping Pong Demo.

11. Make Your Own Bitball

12. Marble Machines – Make your own programmable Fridge-Its, marble mazes, chain
reactions, mini-golf (micro-golf), or pinball.

13. Following Eyes – Use a sonar or infra-red position sensor and servo motors to make
a pair of eyes that follow you around the room..


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14. Make Your Own Sensor – Build a shadow sensor, or another simple sensor in the
spirit of the Radio Shack / Forest Mims books. Pinwheel and reflectance sensor to sense
wind speed; use it to blow out electronic birthday candles…

15. Make Your Own Electronic Test Equipment – What do if you can’t afford an
oscilloscope. Build something that can tell if the ―clock‖ on a newly constructed
LogoChip is running. Make a high speed logic analyzer, a digital voltmeter, or a simple
logic probe.

16. Make Your Own Scientific Instrument – Data collection as in Brian’s Bike Project
or the Chocolate Walk.

17. Make Your Own Things – Connect a LogoChip to stepper motors and use the
controlled motion to make things. You could make art, as Bruce Shapiro’s at the Science
Museum of Minnesota has done.

         Or, if you want to make some of your LogoChip projects more permanent and
         robust than what you get by building on a breadboard, you might want to make
         your own printed circuit boards. Imagine starting with a stock printed circuit
         board that has a 0.1" grid of standard plated-through holes. Thin traces connect
         each pad to each of its 4 nearest neighbor pads. Use the LogoChip, stepper motors
         and a suitable mechanical rig to build a computer controlled ―engraver‖ that had
         sufficient resolution to cut any desired trace. Then one could end up with any
         desired set of connections between holes simply by cutting all the appropriate
         traces and leaving only the ones you wanted. Electronic parts could then be
         soldered in place. The machine requirements to implement this seem very loose
         by CNC standards (you could get away with something like +/- 0.02" accuracy
         over a bed of 3" x 3" or so in the x-y directions and minimal motion in the z-
         direction). The mechanical rig could therefore make use of something that is both
         cheap and available. Perhaps it could be constructed using LEGO Technic or the
         Fischer-Technik plotter. (A commercial computer controlled engraver like the
         Roland EGX-20 (list price $2495) could easily do this job, but that wouldn’t be as
         much fun.) Obviously this invention could also be used as a more general purpose
         personal fabricator.

18. Communicating Crickets – Communicate between two LogoChips by exchanging
beeps, infra-red signals, water drops or smoke signals. Meme cycles: exchange messages
between bikes equipped with spoke speedometers.

19. Smart Coffee Cup – Keeps your coffee at the perfect temperature.

20. Think of 20 More Things To Do With A LogoChip

Other LogoChip Projects:

     AM radio – set PWM to 600 kHz square wave and toggle it on and off at audio
    frequencies to send notes to an AM radio in the next room. Burglar alarm



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   Instrument a potato cannon with a LogoChip equiped with an accelerometer

   Build Your Own Reflectance sensor; (including Build Your Own Lock in:


       to lockin
       setamount 0
       repeat 32 [
       led-on mwait 1
       setamount amount + sensor-reading
       led-off mwait 1
       setamount amount - sensor-reading]
       output amount
       end




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Appendix: An Outline for The Gizmology Project Book
Obviously this section needs a lot of work…

One organizational framework would be the group the projects thematically along the
following lines

1. Visualization and Measurement (e.g. LogoLights, bike speedometer, Make Your
Own Strobe)

2. Control and Feedback (e.g. Braitenberg Creatures, Smart Coffee Cup, Make Your
Own Things)

3. Signals and Systems (e.g. Make Your Own Music, Communicating LogoChips)

What’s the Big Idea? - This could be the title of one of the concluding chapters of the
book. It could provide a list of the ―big ideas‖ and look back to see the various ways in
which the ideas come up in the context of the different projects.



            soft vs. hard; supports tinkering iteration and
           debugging.




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