Transcript Battery Tester Lab Introduction - CEENBoT / TekBot Site

NSF SPIRIT Workshop
2007
Day 1:
1st Electronics Engineering
Project
Build Your Own Battery Tester
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!
Light Emitting Diodes
(or LEDs)
• A diode is a semiconductor electronic device.
–
–
–
–
Form numbers on digital clocks,
Transmit information from remote controls,
Tell you when appliances are turned on
Form images on a jumbo television screen or illuminate a traffic
light.
• A semiconductor is a material with varying ability
to conduct electrical current
Reference: http://electronics.howstuffworks.com/led1.htm
Semiconductor Basics
• Semiconductors are
made from a poor
conductor that has had
impurities (atoms of another
material) added to it. This
process is called doping.
• When these two materials
are joined, a P-N
Junction is formed.
• A semiconductor with
extra electrons is called
N-type material, since it
has extra negativelycharged particles.
• A semiconductor with
extra holes is called
P-type material, since it
has extra positivelycharged particles.
At a P-N Junction, electrons can jump from hole to hole, moving
from a negatively-charged area to a positively-charged area. The
holes appear to move in the opposite direction. This Flow of
Charge is called Current!
The Diode:
a tiny “P-N Junction”!
A diode comprises a section of N-type material bonded to a section of P-type
material, with electrodes on each end. This arrangement conducts electricity in
only one direction.
When no voltage is applied, to the diode, electrons from the N-type material
fill holes from the P-type material along the junction between the layers,
forming a depletion zone. In a depletion zone, the semiconductor material is
returned to its original insulating state -- all of the holes are filled, so there are
no free electrons or empty spaces for electrons, and charge can't flow.
Ah-hah! Let’s put a Battery to it!
To get rid of the depletion zone, you have to get electrons moving
from the N-type area to the P-type area and holes moving in the
reverse direction.
To do this, you connect the N-type side of the diode to the negative
end of a circuit and the P-type side to the positive end.
The free electrons in the N-type material are repelled by the
negative electrode and drawn to the positive electrode. The holes in
the P-type material move the other way. When the voltage
difference between the electrodes is high enough, the
electrons in the depletion zone are boosted out of their holes
and begin moving freely again. The depletion zone disappears,
and charge moves across the diode.
What happens if we Reverse it?
If you try to run current the other way, with the P-type side
connected to the negative end of the circuit and the N-type side
connected to the positive end, current will not flow. The negative
electrons in the N-type material are attracted to the positive electrode.
The positive holes in the P-type material are attracted to the negative
electrode. No current flows across the junction because the holes and
the electrons are each moving in the wrong direction. The depletion
zone increases.
LED, You Light Up My Life!
The interaction between electrons and
holes in this setup has an interesting
side effect -- it generates light!
HOW Does a Diode produce light?
Summary
• 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 across the
diode.
Battery Tester
• Use a LED to build a circuit that will show a
good battery from a bad battery.
+
DIODE -
• Connected Correctly, A Good Battery will
Light up the LED!
Let’s Design the Circuit
• OHM’s LAW will help guide how we design
the battery tester circuit.
• OHM’s LAW states:
• Voltage = Current X Resistance
V=IxR
• Here,
• V = Voltage has units Volts
• I = Current has units Amps
• R = Resistance has units Ohms
Let’s Design the Circuit
• The conceptual design
of the battery tester
circuit (shown at right)
will allow a very high
(almost infinite) current
to flow across the diode.
• To prevent exceeding
the current spec of the
diode, we will use Ohm’s
Law to limit the current.
+
DIODE -
V=IR
Let’s Design 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
• Simply put, solve the equation!
• (The components have been selected for
you and will be provided in the lab.)
Battery Tester Circuit
Thus using Ohm’s Law, we arrive at the final Battery Tester Circuit design
shown in this schematic:
+
+
BATTERY
-
-
RESISTOR
Used to limit
current.
How?
V=IxR
Build Battery Tester Circuit
• A fundamental skill needed to assemble
electronic projects is that of soldering.
• The idea is simple: 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
Build Battery Tester Circuit
in Lab
• Get components for
battery tester circuit:
– LED
– Resistor
– Battery Leads
• Attach these
components on a
circuit board & solder
connections between
them.
Photographs © 1996-2006 Alan Winstanley WORLD
COPYRIGHT RESERVED
Build Battery Tester Circuit
in Lab
• RESOURCES:
• Online Soldering
Guide
• Engineering Staff
• Equipment in Rooms
305 & 311
Photographs © 1996-2006 Alan Winstanley WORLD
COPYRIGHT RESERVED
References
•
Information & Photo Source – Slides 3 through 10
– How Stuff Works: http://electronics.howstuffworks.com/led1.htm
•
Copyright Notice – Information on Slide 13 & Photos Slide 14
– 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 Nebraska-Lincoln, July 2006;
updated July 2007