Transcript PPT

Maintain VEX Rechargeable
Power Packs
Available at: www.etcurr.com
Lesson 1.1 – maintain VEX rechargeable power pack
Maintain VEX Rechargeable
Power Packs
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Performance Objective: Given a VEX robotics system, maintain
VEX rechargeable power packs so the system functions as
required.
Enabling Objectives:
define the following terms: ohms, volts, milliamps, amp hours,
electricity, alternating current, direct current
identify 7.2V and 9.6V power packs
test power pack voltage using a multimeter
explain how to charge the 7.2V power pack versus the 9.6V power pack
set-up the battery charger
identify the charging sequence when charging two power packs
describe the relationship between the status lights on the charger and
the condition of the power pack(s) being charged
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Lesson 1.1 – maintain VEX rechargeable power pack
Battery Packs
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7.2 volt robot battery
Capacity: 1000-2000 mAh
Charging time: 1.4 – 2.8 hrs
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9.6 volt transmitter battery
Capacity: 700 – 1000 mAh
Charging time: 1.4 – 2.0 hrs
NOTE: the batteries used to power VEX
systems are also known as power packs
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Lesson 1.1 – maintain VEX rechargeable power pack
Electricity
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Electricity is the movement of electrons;
particles with a negative charge.
Electrical systems utilize either
alternating current (AC) or direct current
(DC).
VEX robotic systems utilize batteries that
supply DC.
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Lesson 1.1 – maintain VEX rechargeable power pack
Electrical units of
measurement
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There are three units of measure that
are important when looking at an
electrical circuit:
 Amps
 Volts
 Ohms
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Lesson 1.1 – maintain VEX rechargeable power pack
Amps (A)
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Amps is the measure of electrical
current.
Current is the amount of electrons
flowing through a conductor in a given
period of time.
Amps can be measured using a
multimeter.
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Lesson 1.1 – maintain VEX rechargeable power pack
Volts (V)
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Volts is the measure of force or pressure
moving electrons.
Volts can also be measured using a
multimeter.
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Lesson 1.1 – maintain VEX rechargeable power pack
Ohms (Ω)
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Ohms is the measure of resistance to the
flow of electrons.
Multimeter can be used to measure
ohms.
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Lesson 1.1 – maintain VEX rechargeable power pack
Digital Multimeter
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A multimeter can
be used to
measure both AC
and DC voltage,
amperage, ohms,
and continuity.
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Lesson 1.1 – maintain VEX rechargeable power pack
Digital Multimeter
Ohms
AC Volts
DC Volts
DC Amps
DC millivolts
AC Amps
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Continuity
Lesson 1.1 – maintain VEX rechargeable power pack
Measuring DC Voltage
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Step 1: Set
multimeter on DC
voltage
Step 2: Plug red
probe in volts, ohms,
and continuity socket
Step 3: Be sure black
probe is in the com
socket
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Lesson 1.1 – maintain VEX rechargeable power pack
Measuring DC Voltage
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Step 4: Place probes in
socket of battery pack,
red to red (+), black to
black (-)
Step 5: Note voltage
value from the
multimeter
If reading is negative,
you can either ignore the
minus sign or reverse the
probes
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Lesson 1.1 – maintain VEX rechargeable power pack
Normal battery readings
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A freshly charged 7.2 V (nominal value)
battery will read approximately 8.2 volts
A freshly charged 9.6 V(nominal value)
battery will read approximately 10.4
volts
When a battery reaches its nominal
value, it will need to be recharged
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Lesson 1.1 – maintain VEX rechargeable power pack
CAUTION using multimeter
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DO NOT test the
batteries using any
other set-up on
the multimeter or
you may risk
damaging the
multimeter.
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Lesson 1.1 – maintain VEX rechargeable power pack
Milliamp-hours (mAh)
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An amp-hour is the amount of amps a battery
can deliver for one hour
The prefix milli is used to indicate one
thousandth (1/1000) of a unit in the SI
measurement system
For example: a millimeter (mm) is one
thousandth (1/1000 or 0.001) of a meter; a
milliamp-hour (mAh) is 0.001 of an amp-hour.
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Lesson 1.1 – maintain VEX rechargeable power pack
Milliamp-Hours (mAh)
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2000 mAh
The battery can produce a
steady charge of 2 amps for
one hour
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1000 mAh
The battery can produce a
steady charge of 1 amp for
one hour
Lesson 1.1 – maintain VEX rechargeable power pack
Battery Charger
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Battery charger
and battery
packs
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Transformer and
chord
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Lesson 1.1 – maintain VEX rechargeable power pack
Setting up the battery
charger
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Plug transformer ‘s
120VAC cord into
wall outlet
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Plug transformer’s
16VDC cord into the
battery charger
Lesson 1.1 – maintain VEX rechargeable power pack
Battery charger default
setting
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Battery packs
properly installed
in charger
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Default override switches:
These switches will be
engaged when the 7.2
Volt battery is properly
installed
Lesson 1.1 – maintain VEX rechargeable power pack
Properly inserting batteries
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When charging 7.2 volt
batteries it is very
important the default
override switches are
pressed down. If these
switches are not pressed
down, the 7.2 battery pack
will be charged to the
higher default setting,
ruining it.
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Switch is pressed
Lesson 1.1 – maintain VEX rechargeable power pack
Charging order of batteries
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Whichever battery is
plugged in first is the
first one to charge.
The second battery
will be charged when
the first is completely
charged.
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Lesson 1.1 – maintain VEX rechargeable power pack
LED Status lights
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Whichever LED is on indicates which battery is
charging
If the LED is flashing it indicates there is a
problem
If the LED is off it means the battery is fully
charged or waiting for the other battery to
charge
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Lesson 1.1 – maintain VEX rechargeable power pack
Flashing LED
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If LED flashes, try a different battery
pack
If the LED still flashes, try another
charger
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Lesson 1.1 – maintain VEX rechargeable power pack
The End
Have fun and be safe
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Lesson 1.1 – maintain VEX rechargeable power pack