Mini-Lecture Series - Team 3176 Purple Precision

Mini-Lecture Series - Team 3176 Purple Precision
Mini-Lecture Series
Team 3176 Off-Season
Engineering Orientation
Electricity & Electronics
Previous Lectures…
Electricity & Electronics
• The primary source of power for the robot is
the electrical battery. It is key to understand
the efficient use of this power and how to
control it safely.
• In this mini-lecture, we’ll cover
– Some basic electrical concepts
– Review robot components
– Design considerations
Electricity Basics
• All matter is made up of atoms
– Protons, Neutrons, & Electrons
– Applying external force we can move electrons
• Movement through a magnetic field, heat, friction, or a
chemical reaction
Characteristics of Electricity
• Voltage (E or V) – difference in charge in circuit
– Measured in Volts (V)
• Current (I) – flow rate in the circuit
– Measured in Amperes (A)
• Resistance (R) – tendency to resist the flow
– Measured in Ohms ()
– Conductors vs. Insulators
Ohm’s Law
• These three characteristics (V, I, R) are related
in a simple equation:
– V=IxR
–
–
•
•
or I = V / R
or R = V / I
Electrical designers use Ohm’s Law to determine how much
voltage is required for a certain load, like a motor, a computer,
or even a house full of appliances.
Remember, Power is related to Voltage and Current
– P = I x V = I2 x R
Battery
•
•
The power supply for an FRC robot is a single 12V 18Ah
battery.
The batteries used for FRC are sealed lead acid batteries
capable of meeting high current demands of an FRC robot.
Breakers / Fuses
•
The 120A Main Circuit Breaker serves two roles:
–
–
•
•
Main robot power switch
Protection device for downstream robot wiring and components
The 120A circuit breaker is wired between of the battery and
Power Distribution Panel.
The circuit breakers are also used on the Power Distribution
Panel to limit current to branch circuits.
Power Distribution Panel
Voltage Regulator Module
•
•
The Power Distribution Panel (PDP) distributes power from a
12VDC battery to various robot components through autoresetting circuit breakers and a small number of special function
fused connections.
VRM provides regulated power for the robot radio, custom
circuits, and IP vision cameras.
roboRIO
•
•
The NI-roboRIO is the main robot controller (the “brains”).
Integrated controller I/O includes a variety of communication
protocols (Ethernet, USB, CAN, SPI, I2C, and serial) as well as
PWM, servo, digital I/O, and analog I/O channels used to connect
to robot peripherals for sensing and control.
Wireless Bridge
•
•
Motor Controller
The wireless radio is used as the robot radio to provide wireless
communication functionality to the robot. The device can be
configured as an Access Point for direct “tethered” connection to
a laptop.
The Talon SRX motor controller varies power to the motors as
controlled by the roboRIO signals.
Design Considerations
• Wire Gauge
– Current capacity and resistance
• Higher Gauge = Smaller Wire (e.g., 14 AWG)
– Wire routings – excessive lengths leads to losses
• Number of Motors / Controllers / Sensors
• Battery access
– We need a fresh battery for every round
– Ease of access vs. stable placement (low center)
• Safety
– Keep wires insulated and free from moving
components
– Loose wires and metal components don’t mix!
Questions?
Sources:
http://www.electronicstheory.com/
http://www.eaton.com/flash/electrical/101series/Fundamentalsof_Electricity/story.html
https://learn.sparkfun.com/tutorials/voltage-current-resistance-and-ohms-law
http://wpilib.screenstepslive.com/s/4485/m/13503/l/599672-2016-frc-control-systemhardware-overview
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