Today’s Agenda
So you want to build some crazy Ubicomp stuff....
Week Three:
Circuits and Soldering
Ubicomp Projects: Informatics 190
Gillian Hayes
February 6, 2008
Guest Speakers
• Questions/Comments from Gloria’s lecture
last week
• Upcoming:
• Tico Ballagas, 2/27
• Trevor Pering, 3/5
Voltage and Current
• Voltage is like Volume
• Current is like Flow
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Guest Speakers
Your homework projects
Basics of Circuit Design
Soldering
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What is it?
How to do it?
Some simple soldering projects
Homework
• Awesome Job! Very creative low-fi
prototypes
• If you haven’t done so already, please turn
in your team assessments of yourself and
your team-members
Resistors
Symbol for American
Resistor
• Two-terminal electronic component
• Opposes an electric current by producing a
Symbol for American
Variable Resistor
voltage drop between its terminals
• Ohm’s Law: R = V/I
(electrical resistance is equal to the voltage drop across the
resistor divided by the current through the resistor)
Capacitors
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(c) Howstuffworks 2007
stores electrons
like a battery that can dump all its electricity in a few seconds
and can’t create new electron
Transistors
• semi-conductor device
• used to amplify or switch electronic signals
Capacitive Touch Screens (like the iPhone)
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glass screens that have a very thin, transparent metallic coating
built-in electrode pattern charges the screen
when touched, current is drawn to the finger, creating voltage drop
exact location picked up by a controller and transmitted to a
computer
Series and Parallel Circuits
Want to Know More
about Circuit Design?
Series
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Two or more components connected end to end
Same current flows through them all
Parallel
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Two or more components connected
like the rungs of a ladder
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Components split the current
Soldering
"the joining of metals by a
fusion of alloys which have
relatively low melting
points"
in other words... soldering
is like gluing two pieces of
metal together with molten
Take an EE class... I only know enough to
build what I want for people to interact with
ubicomp stuff
What do you
need to solder?
Choosing solder
Be careful
• Rosin core solder releases fumes
• Don’t lean too close
• Work in well-ventilated area
• Hot solder is very dangerous
• Don’t splash it around
• Mind your hands
• NEVER use acid core solder
• Best is thin rosin core solder
• Don’t get anything too thick for electronics
work
Preparing the Surface
Applying the Solder
• Clean surface is important for a low
resistance joint
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• Steel Wool
• Sand paper
Solvent
Clean-up
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Apply a very small amount of solder to the tip
of the iron
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Heat up the lead and the component to be hot
enough for the solder
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Touch the tip of the solder to the component
lead and solder pad, but NOT the tip of the iron
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Don’t move the joint, let it cool
Helpful tips
• Solvent and steel wool can help get rid of
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Use heatsinks. Heatsinks are a must for the leads of sensitive components such as
ICs and transistors. If you don't have a clip on heatsink, then a pair of pliers is a good
substitute.
• You can coat the bottom of the board with
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Keep the iron tip clean. A clean iron tip means better heat conduction and a
better joint. Use a wet sponge to clean the tip between joints.
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Double check joints. It is a good idea to check all solder joints with an ohm
meter after they are cooled. If the joint measures any more than a few tenths of an
ohm, then it may be a good idea to resolder it.
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Use the proper iron. Remember that bigger joints will take longer to heat up
with an 30W iron than with a 150W iron. While 30W is good for printed circuit
boards and the like, higher wattages are great when soldering to a heavy metal
chassis.
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Solder small parts first. Solder resistors, jumper leads, diodes and any other
small parts before you solder larger parts like capacitors and transistors. This makes
assembly much easier.
leftover rosin
laquer to prevent oxidation
Front-side of
a completed
circuit
Back-side of
a completed
circuit
But what if I don’t want
to solder?
• Use a breadboard!
• Reusable solderless device
• Used to build a prototype of an electronic
circuit for experimenting with circuit designs
Good Links for More Help
http://www.instructables.com/id/How-to-solder/
Ubicomp Development: http://www.comp.lancs.ac.uk/
~albrecht/ubidev/devtools.htm
Soldering electric guitar components: http://
www.kingbass.com/soldering101.html
http://www.elexp.com/t_solder.htm
some fun projects: http://www.kpsec.freeuk.com/proj.htm
Today: Simple LED Flashlight
The
basics
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Connect the positive
to the positive
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These LEDs are 3V
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If your battery is
more, you need a
resistor
If your battery is less,
you need multiple
batteries