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Soldering and
Building a
Battery Tester
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Build Your Skills
OBJECTIVES:
Learn to Solder
Learn how the circuit components
work in a simple circuit used to test a
battery.
Gain exposure to the fundamental
law of circuit design – Ohm’s Law.
Build the circuit in lab.
Take it with you!
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Light Emitting Diodes
(or LEDs)
A
diode is a semiconductor electronic
device.
A
semiconductor is a material with a variable
ability to conduct electrical current.
Reference: http://electronics.howstuffworks.com/led1.htm
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Light Emitting Diode
A
Diode is a common component in
many electronic applications.
 A Diode is a P-N junction that allows
current to pass in only 1 direction,
under the right conditions.
 Light-emitting diodes, or LED’s emit
light when current is flowing through
the diode.
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Battery Tester
 Use
a LED to build a circuit that will
indicate a good battery.
+ DIODE -
 Connected
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Correctly, A Good Battery
will Light up the LED!
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Designing the Circuit
 OHM’s
LAW will help guide how we
design the battery tester circuit.
Voltage = Current X Resistance
V=IxR
 Here,
V = Voltage has units Volts
I = Current has units Amps
R = Resistance has units Ohms
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Designing the Circuit

The conceptual design
of the battery tester
circuit (shown at right)
will allow a very high
(almost infinite) current
to flow through the
diode.

To prevent exceeding
the current spec of the
diode, we will use
Ohm’s Law to limit the
current.
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+
DIODE -
V = IR
Designing the Circuit
 Rearranging
V=IR, we see I = V/R.
 Choose
a resistance R to achieve a
current, I = V/R, that will be at a safe
level for the diode, given the set
value of V (e.g. 9 volt battery).
V = IR
 Solve
the equation.
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Battery Tester Circuit
Thus using Ohm’s Law, we arrive at the final Battery Tester
Circuit design shown in this schematic:
+
+
-
-
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Building the Battery Tester Circuit
 Soldering
is a fundamental skill
needed to assemble electronic
projects.
 The idea: Join electrical parts together
to form an electrical connection.
 Use a molten mixture of lead and tin
(solder), together with a soldering
iron.
For more information, see: http://www.epemag.wimborne.co.uk/solderfaq.htm
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Soldering Electronic Circuits
 Get
components for
battery tester
circuit:
 LED
 Resistor
 Battery Leads
 Insert
the
component.
 Splay the leads to
hold the component
in place.
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Photographs © 1996-2006 Alan Winstanley WORLD COPYRIGHT RESERVED
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Building the Battery Tester Circuit

Apply a clean
soldering iron tip to
the copper solder pad
and the component
lead, in order to heat
both items at the
same time.
 Continue heating and
apply a few mm. of
solder.
 Remove the iron and
allow the solder joint
to cool naturally.
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Photographs © 1996-2006 Alan Winstanley WORLD COPYRIGHT RESERVED
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Building the Battery Tester Circuit

The joint should be
nice and shiny.
A
bad joint: the
solder failed to flow,
and instead beaded
to form globules
around the wire.
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Photographs © 1996-2006 Alan Winstanley WORLD COPYRIGHT RESERVED
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Soldering Summary


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






All parts must be clean and free from dirt and grease.
Try to secure the work firmly.
"Tin" the iron tip with a small amount of solder. Do this
immediately, with new tips being used for the first time.
Clean the tip of the hot soldering iron on a damp sponge.
Many people then add a tiny amount of fresh solder to the
cleansed tip.
Heat all parts of the joint with the iron for under a second or
so.
Continue heating, then apply sufficient solder only, to form
an adequate joint.
Remove and return the iron safely to its stand.
It only takes two or three seconds at most, to solder the
average p.c.b. joint.
Do not move parts until the solder has cooled.
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References

Information & Photo Source

Copyright Notice
 How Stuff Works: http://electronics.howstuffworks.com/led1.htm
Everyday Practical Electronics Soldering Guide:
http://www.epemag.wimborne.co.uk/solderfaq.htm
 Text © 1996-2006 Wimborne Publishing Limited, Wimborne, Dorset, England.
Everyday Practical Electronics Magazine has provided this document as a
free web resource to help constructors, trainees and students. You are
welcome to download it, print it and distribute it for personal or educational
use. It may not be used in any commercial publication, mirrored on any
commercial site nor may it be appended to or amended, or used or distributed
for any commercial reason, without the prior permission of the Publishers.
 Photographs © 1996-2006 Alan Winstanley WORLD COPYRIGHT
RESERVED

Presentation Created by: Alisa N. Gilmore, P.E. Department of
Computer and Electronics Engineering, University of NebraskaLincoln, July 2006; updated July 2007; modified June 2009 by H. D.
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