Transcript Fasteners (Background)

Test Bed Assembly
Vex 1.0 © 2005 Carnegie Mellon Robotics Academy Inc.
How do we teach the concepts?
Vex 1.0 © 2005 Carnegie Mellon Robotics Academy Inc.
What purpose does this TEST
BED serve?
• Teaches or refreshes
electrical concepts
• Applies theoretical
concepts
• Prepares the student
for the future
• Competition –
Motivates Students
Vex 1.0 © 2005 Carnegie Mellon Robotics Academy Inc.
Concepts Covered?
• Build a teaching tool
capable of showing
multiple theoretical
principles.
• Experience working with
electrical and electronic
controls
• Help the instructor and
students build a safe,
uncluttered teaching tool.
Vex 1.0 © 2005 Carnegie Mellon Robotics Academy Inc.
Board Construction
Vex 1.0 © 2005 Carnegie Mellon Robotics Academy Inc.
Vex Controller
Vex 1.0 © 2005 Carnegie Mellon Robotics Academy Inc.
Vex Limit Switch
Vex 1.0 © 2005 Carnegie Mellon Robotics Academy Inc.
Vex Bump Switch
Vex 1.0 © 2005 Carnegie Mellon Robotics Academy Inc.
Vex RF Receiver Module
Antenna and Holder
Vex 1.0 © 2005 Carnegie Mellon Robotics Academy Inc.
Vex Crystal and Cable
Vex 1.0 © 2005 Carnegie Mellon Robotics Academy Inc.
Main Switch
Vex 1.0 © 2005 Carnegie Mellon Robotics Academy Inc.
Main Switch
• Controls flow of
current from battery
• Mounted before the
fuse panel
• Provides an
“Emergency Stop”
control in the system
• Schematic Symbol for
“Single Pole, Single
Throw” switch
Vex 1.0 © 2005 Carnegie Mellon Robotics Academy Inc.
Terminal Block
Vex 1.0 © 2005 Carnegie Mellon Robotics Academy Inc.
Terminal Block
• Allows multiple
connection access.
• Allows use of smaller
wire to feed multiple
accessories.
Vex 1.0 © 2005 Carnegie Mellon Robotics Academy Inc.
Fuse Panel
Vex 1.0 © 2005 Carnegie Mellon Robotics Academy Inc.
Fuse Panel
NEGATIVE (-) = BLACK
POSITIVE (+) = RED
Vex 1.0 © 2005 Carnegie Mellon Robotics Academy Inc.
Circuit Protection
Vex 1.0 © 2005 Carnegie Mellon Robotics Academy Inc.
Circuit Protection
The most common types of circuit protection are fuses and
circuit breakers.
Vex 1.0 © 2005 Carnegie Mellon Robotics Academy Inc.
Fuses
Parts of a blade type fuse
Why doesn’t it work?
Vex 1.0 © 2005 Carnegie Mellon Robotics Academy Inc.
Relay 1
Vex 1.0 © 2005 Carnegie Mellon Robotics Academy Inc.
Solid-State / Electro-Mechanical Relay
• Spike is a 20 Amp, HBridge Relay Module that
is small enough to be
remotely mounted almost
anywhere on your robot.
Spike is designed for
driving small motors in
forward, reverse, or stop
(brake). Spike is optoisolated at the signal
input to protect the Robot
Controller against motor
noise and return currents.
Vex 1.0 © 2005 Carnegie Mellon Robotics Academy Inc.
Solid-State / Electro-Mechanical Relay
How it Works
Vex 1.0 © 2005 Carnegie Mellon Robotics Academy Inc.
Relay 2
Vex 1.0 © 2005 Carnegie Mellon Robotics Academy Inc.
Pulse Width Modulation Controls
PWM 1
Vex 1.0 © 2005 Carnegie Mellon Robotics Academy Inc.
PWM
• What is pulse width
modulation?
• What type of wave is
produced?
• What makes the
PWM different from a
Solid State electromechanical relay?
Vex 1.0 © 2005 Carnegie Mellon Robotics Academy Inc.
PWM
• PWM’s work on the
principle of square
waves
• Longer duty cycles
increase the amount
of time the motor runs
• Result : more speed
or braking power
Vex 1.0 © 2005 Carnegie Mellon Robotics Academy Inc.
PWM
Vex 1.0 © 2005 Carnegie Mellon Robotics Academy Inc.
Pulse Width Modulation Controls
PWM 2
Vex 1.0 © 2005 Carnegie Mellon Robotics Academy Inc.
Electron Flow
For our purposes, we will use the conventional
theory stating that current flows from negative (-)
to positive (+).
Vex 1.0 © 2005 Carnegie Mellon Robotics Academy Inc.
Electrical Wiring
• Wires or conductors, carry the current
throughout the circuit
• Proper wire size (gauge) is important and may
be determined a couple of ways
– Mathematical Formula
– Charts
• Size and capacity is rated by professional
organizations like AWG (American Wire Gauge).
Vex 1.0 © 2005 Carnegie Mellon Robotics Academy Inc.
How Do I Know What Wire to Use?
•
Wires come in different sizes. The maximum current each size can
conduct safely is shown.
• Make sure the wire is capable of carrying the current load.
• Check what the supply Voltage be.
NOTE: When it is critical that voltage reduction is minimal, use a larger
diameter wire.
Vex 1.0 © 2005 Carnegie Mellon Robotics Academy Inc.
Main Switch
Vex 1.0 © 2005 Carnegie Mellon Robotics Academy Inc.
Terminal Block
Vex 1.0 © 2005 Carnegie Mellon Robotics Academy Inc.
Relay 1
Vex 1.0 © 2005 Carnegie Mellon Robotics Academy Inc.
Relay 2
Vex 1.0 © 2005 Carnegie Mellon Robotics Academy Inc.
PWM 1
Vex 1.0 © 2005 Carnegie Mellon Robotics Academy Inc.
PWM 2
Vex 1.0 © 2005 Carnegie Mellon Robotics Academy Inc.
PWM Control Cables
Vex 1.0 © 2005 Carnegie Mellon Robotics Academy Inc.
Relay Control Cable
Vex 1.0 © 2005 Carnegie Mellon Robotics Academy Inc.
Test Motors
Vex 1.0 © 2005 Carnegie Mellon Robotics Academy Inc.
Batteries
SAFETY
Always make sure the
battery is disconnected
before working on any part
of the circuit or
components. Always make
sure the battery is
disconnected and removed
from the testbed when it is
not in use. Always store the
battery in a secure, dry
place.
Vex 1.0 © 2005 Carnegie Mellon Robotics Academy Inc.