View
219
Download
1
Category
Preview:
Citation preview
Vex 1.0 © 2005 Carnegie Mellon Robotics Academy Inc.
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 ModuleAntenna 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.
• 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
Main 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.
The most common types of circuit protection are fuses and circuit breakers.
Circuit Protection
Vex 1.0 © 2005 Carnegie Mellon Robotics Academy Inc.
Parts of a blade type fuse
Why doesn’t it work?
Fuses
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, H-Bridge 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 opto-isolated 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 ControlsPWM 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 electro-mechanical 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 ControlsPWM 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.
• 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).
Electrical Wiring
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
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.
SAFETY
Recommended