Welcome to Electrical

Mentors

Austin Russell

Ricardo Ortiz

James Corcoran

Austin

  • Network & Cyber Security Engineer
    • Groton Utilities
  • Student on the team for 2013 & 2014 season, now mentor for the past year
  • New England Institute for Technology, September 2017
    • Associate of Science, Network Engineering
    • Bachelor of Science, Network Engineering & Cyber Security
  • Other than just electrical, I manage the IT and computer systems for the team, as well as anything else that needs to be done

Ricardo

  • TODO

James

  • Software Engineer at Electric Boat
    • Move air, water, and metal with electrons and dinosaurs
  • Electrical/Programming mentor on FRC2168 since 2008
  • BS Computer Engineering from Rochester Institute of Technology
  • I like to learn about new & random stuff:
    • Space, 3D Printing, Computer Vision, Flat Earth Society?
    • Micro controllers, Artificial Organs, Information Security
    • CNC, Lego, Cheap stuff from China, Linux, Pyrotechnics,
    • Test Automation, Wood working, primitive technologies
    • Robotics!, Web Design, Statistics, Photo editing, ...

Course Topics

  • Motor Controllers
  • Motors
    • DC Motors
    • Servos (Rotary/Linear)
  • RoboRIO
  • VRM
  • Radio
  • Sensors
    • Encoders, Gyro, potentiometers
    • Boolean (Mechanical Switches, Hall effects, IR proximity)
    • IR rangingsensors
  • Pneumatics
    • PCM
    • Solenoids
    • Acutators

Overview

Topics to cover

  • Team role
  • Interfacing with other disciplines
  • Build season role
    • Prototype support
    • Final wiring
    • Criticality of our work
    • Aware of design decisions for seamless autos
  • Hardware overview

Team Role / Discipline Interaction

  • Electrical
    • Mechanical
      • Aid prototype development
    • Programming
      • Determine the right sensors for the job
    • CAD
      • Plan component placement
    • Drive Team
      • Custom controls & Automation

Build Season Role

  • Week 1 - 3
    • Test which sensors work for detecting game elements
    • Source components for games specific features
    • Support prototype wiring
  • Week 4 - 6
    • Plan out electrical layout for comp bot
    • Wire practice & comp bot
  • Week 6+
    • Keep the robot running at events
      • Fix broken wires, sensors, etc
    • Wire up new mechanisms & design revisions
    • Figure out what doesn't work, find solutions

Hardware Overview

Battery

The brains of the operation.

  • 12V Sealed Lead Acid Battery
  • Like what you'd find on a motorcycle or lawnmower
  • All power for robot operation must come from ONE battery.
  • Can supply 100s of Amps
    • Respect the batteries and don't get hurt!

Main Breaker

High current (120A) circuit breaker.

  • Main robot power switch
    • OFF - Depress red button
    • ON - Close black lever 
  • Open circuits when high current drawn for long duration of time
  • Prevents fires, causes tears
    • Design bot to never pop

Power Distribution Panel (PDP)

Distributes power from the battery to all components on the robot.

  • Up to 8 40A circuts
  • Up to 8 30A circuits
  • Special 10A & 20A circuits for peripherals 

Auto-Resetting Circuit Breaker

Different sizes (40A, 30A, 20A)

  • Protect hardware from blowing
  • 40A breakers for powerful motors
  • 30/20A breakers for 
  • After heating up (high current), these open circuit
  • Once cool they will automatically close and send power back to downstream componet

Pneumatics Control Module (PCM)

Allows control of pneumatics components over CAN bus

  • Control up to 8 solenoid channels
  •  Turn compressor on/off compressor

Voltage Regulator Module (VRM)

Provides regulated supply voltages

  • 12V 2A
    • 500mA section counts towards 2A limit
  • 5V 2A
    • 500mA section counts towards 2A limit

RoboRIO

The brains of the operation.

  • Runs our code
  • Controls all outputs
  • Reads all inputs
  • Talks back to driver station laptop 
  • Interfaces
    • PWM
    • Digital Inputs/Outpus
    • Relay Channels
    • Analog inputs
    • MXP expansion header

Motor Controllers

Control speed and direction of motors

  • Many different kinds
    • SPARK, Victor 888, Talon, Victor SP, Talon SRX
  • Controlled by roboRIO over
    • PWM
    • CAN
  • Don't plug in backwards
    • Expensive learning experience

Robot Radio

Standard WIFI Radio (802.11)

  • Can be configured as Access Point
    • For use at home
  • Wireless Client 
    • For use at competitions

SPIKE Relay module

Contains two relays (switches)

  • Not terribly common
  • Can be used to control anything that just needs to be turned on/off (12V).
    • Compressor
    • LEDs
    • Low power motor with no speed control
  • Contains its own 20A fuse

Cameras

Ethernet / USB

  • Used for:
    • Operator feedback
    • Object detection
  • Camera feed can be fed back to driver station or processed locally on the roboRIO

Motors

Topics to cover

  • Intro on voltage, current, resistance

  • Review FRC parts

    • Battery

    • PD board

    • Breakers

    • Motor controllers

  • DC Motors

  • Servo Motors

Voltage/Current/Resistatnce

FRC Parts - Refresher

Find them:

  • Battery
  • PD Board
  • Breakers
  • Motor Controllers
  • RoboRIO
  • Radio
  • VRM
  • PCM

 A                B                   C

                                           D

 

 

                        E

 

 

                        F

   

  G                                       H

MOTOR CONTROLLERS

Motor Controllers

  • Allow motors to be... controlled by the roboRIO
  • Varying degrees of features
    • Some are very simple just speed/direction control
    • Some are complex and can interface directly to sensors and have internal position/speed controllers

 

  • Brake/Coast setting
    • High RPM >> Use COAST!

Brushed DC MOTORS

DC MOTORS

 

  • Magnets mounted around the exterior
    • "stator"
  • Coil of wire at center
    • "rotor"
  • When current flows through the coil it creates a magnetic field that reacts against the field created by the magnets and causes rotary motion

Brushed DC Motors: the most common type of motors used on our robots.

Brushed DC Motors

Lab

Materials Needed

  • Motor tester board with PWM generator

Procedure:

  • Wire up motor tester board to DC Motor
  • Hook up multimeter across input and output of motor controller.
  • Monitor voltage output as motor speed is changed

 

How does the Brake/Coast jumper affect operation?

​What happens when the load is applied to the motor?

SERVO MOTORS

Rotary Position Servos

Command motor to specific angle

  • Can be used for controlling mechanism to specific position
  • Need to take external forces into consideration when choosing part to prevent stripped gears and backdriving

Continuous Rotation Servos

Same as position servos but, control circuitry is modified.

  • Instead of controlling position...
    input controls speed and direction (sound familiar?)
  • These aren't the solution to all out problems though, remember there's still a very small DC motor inside the servo. 

Linear Servo Motors

Command motor to extension

Similar to rotary servo, but extends and retracts

 

  • Gear boxes in some of them can provide a large toque multiplier.
  • Surprisingly strong
  • Easy to break when side loaded

Lab

Materials Needed

  • Motor tester board with PWM generator

Procedure:

  • Wire up motor tester board to servo (directly to PWM generator)
  • Monitor position of servo as the PWM generator moved.

 

What will happen when an external force is applied?

Sensors

Topics to cover

  • Discrete Sensors
    • Switches, Hall effect, 
  • Analog Sensors
    • Potentiometer, SHARP IR, Pressure Sensor
  • Position Sensors
    • Encoders, Gyros, IMUs
  • Cameras

Discrete Sensors

  • Report a Boolean status to the control system
    • On/Off, True/False
  • Examples:
    • Limit switch (Mechanical contact)
    • Hall Effect Sensor (Magnetic field)
    • Proximity Sensor (Metal presence)
    • Photo Detector/Emitter (Light)

Analog Sensors

  • Voltage varies over sensed range
  • Can be used to measure
    • distance, pressure, current, position, etc
  • Analog sensors can be turned into Boolean statuses with logic in robot code:
    • e.g. If voltage >= 2.5 true; else false;

Analog Sensors (cont)

  • Examples:
    • SHARP IR
    • Pressure Sensor
    • Potentiometer
    • Ultrasonic

Encoders

  • Incremental or absolute indication of position
  • Produce a train of pulses
  • Number of pulses can be counted to determine position or speed of component

Gyros

  • Gyro
    • A gyro can be used to measure the robots heading (which way it's facing), usually relative to a calibrated zero
    • Value reported as a rotation rate which is integrated to determine heading
    • Interface can be serial (ADXRS450) or analog (ADW22307)

IMUs

  • Inertial Measurement Unit (IMU)
  • Combine multiple sensors for multi-axis position indication
    • Typically at least a Gyro and Accelerometer
    • Can also include Magnetometers, temperature sensors, etc.
  • Typically provides roll/pitch/heading
  • Some can also provide translation/offset relative to starting position (field oriented).

Camera

  • Used for drive team situational awareness and Autonomous robot navigation
  • Connect to robot over Ethernet or USB
  • Important performance characteristics
    • Resolution (more is not nesc. better)
    • Exposure (calibratable)
    • Image latency

 

Pneumatic Systems

Topics to cover

  • Pneumatic components
  • Pneumatic controls

Air Compressor

  • Convert electric energy into compressed air
  • VIAR 90C
    • Runs off 12VDC, ~10A
    • Rated at 9% duty cycle!!!

Nason Pressure Switch

  • Used by control system to turn compressor on and off
  • Note the labels "NC" and "C"
    • Remember what those mean from our discrete sensors class?
  • Closed circuit when pressure is low

Air Tanks

  • Clippard tanks store 574ml of air ea.
  • Max 125 PSI

Pressure Regulator

  • Similar to voltage regulator but for air
  • Allows stepping high pressures down to lower pressures
    • 120 PSI -> 60 PSI
    •   60 PSI -> 30 PSI 

Pressure relief vlave

  • Releases pressure out of system when above "safe" set point

Pressure Gauge

  • Indicates the pressure accumulated within the system.
  • Can be used to indicate pressure before (high side) or after (low side) regulators

Pneumatic Actuator (Cylinder)

  • Linear actuator
    • Two "ports", one at each end
    • Rod down the middle
    • Tail end of rod seals against inner wall of cylinder
    • Pressure difference across the seal causes rod to extend/retract

Pneumatic Actuator (Cylinder)

  • Extend cylinder
    • Apply pressure to the left of the seal
    • Vent pressure from the right of the seal

 

  • Retract cylinder
    • Apply pressure to the right of the seal
    • Vent pressure from the left of the seal

Solenoid Valve

Electrically control air flow.

  • Solenoids in FRC are either 12 or 24V
  • We typically use "5/3" double solenoid valves
    • 5 physical ports (holes) on it
    • 3 positions the valve can be in
  • Called "double" solenoids because each valve has two solenoids.
  • The solenoids are coils of wire
  • When electricity flows through them it creates a magnetic field.
  • The magnetic field causes the valve to port air in different directions

Solenoid Valve

B: Spring return 

A: Solenoid

What do these symbols mean?!@#

C: Depicting how air will flow between numbered ports for different valve positions

D: Manual actuator

Solenoid Valve Positions

  • Left solenoid energized
  • ​Valve shifts
    • Pressure flows from 1 to 4
    • 2 and 3 are connected allowing 2 to vent
  • Right solenoid energized
  • ​Valve shifts
    • Pressure flows from 1 to 2
    • 4 and 5 are connected allowing 4 to vent

Pneumatics Control Module (PCM)

Allows control of pneumatics components over CAN bus

  • Turn compressor on/off compressor
  • Control up to 8 solenoid channels
    • 8 single acting solenoids
    • 4 Double solenoids

Lab

Wire & Plumb up a simple pneumatic system

  • Compressor turned on/off by Nason pressure switch (through relay for example)
  • Air tank to store pressure from pump
  • Plumb pressurized tank to regulator
    • Set regulator to ~30 PSI
  • Plumb regulator to 5/3 valve (port 1 on previous slide)
  • Plumb outputs of valve (ports 2 & 4) to cylinder

 

  • Apply power to system and verify compressor turns off at right pressure
  • Energize solenoids one at a time
    • Observe behavior of cylinder

Safety

Topics to cover

  • Personal Safety
  • Robot Safety
    • Yes, Robots have feelings too

Personal Safety

  • Safety is always a number one priority
  • We want to keep ourselves safe at all times

Tools that can hurt

  • Cutting tools 
    • Flush cutters
    • Scissors
    • Strippers

Tools that can hurt

  • Heating tools 
    • Soldering Iron
    • Heat gun

Tools that can hurt

  • Crushing/Impact tools 
    • Crimpers

Tools that can hurt

  • Common shop tools
    • Screw drivers
    • Wrenches
    • Pliers
    • etc.

Tools that can hurt

  • Machinery
    • Band Saw
    • Drill Press
    • Drills

How to be safe

  • Always have a mentor present
    • If not sure about something, ask a mentor or student lead
  • Use Personal protective equipment (PPE)
  • Use common sense
  • Think before doing

PPE

  • Safety Glasses
    • Always to be used in shop when machinery is run or mechanical is working
    • Always to be used when soldering
      • Hot liquid metal in the eye is not good
  • Gloves
    • Used when needed
      • Sometimes helpful when soldering when holding wire so you don't burn hands, but can hinder hand articulation and mobility

Robot Safety

  • Robots are expensive
  • Electrical components are almost always the most expensive parts of an FRC robot
  • We want to keep them working

Robot Safety


  • Double check all wiring before robot power is applied
  • When making changes to the electrical or control systems, be sure to have a mentor or student lead verify the changes
    • Mentors qualified to check work
      • James
      • Austin
      • Kevin H
      • Ricardo
    • Student leads qualifed to check work
      • Deidra Hall

Robot Safety

  • Don't short connections
    • A short circuit is an electrical circuit that allows a current to travel along an unintended path with no or a very low electrical impedance. This results in an excessive amount of current flowing into the circuit
  • Verify that the chassis is isolated from the battery power and ground before the main breaker is turned on

Robot Safety

  • Pay attention to what you are doing
    • What
    • Where
    • When
    • Why
    • How
  • Some of the simplest and sometimes biggest mistakes can be due to not following this structure

Robot Safety

  • Pay attention to what is going on around you and the robot
    • Listen for ENABLING
      • RSL will blink when robot is enabled
    • Ensure others are not repairing/tampering/controlling things that will effect what you are doing
    • Ensure that others are not in/around the robot when enabling the robot

Robot Safety

  • Robots can be dangerous
  • Have many different types of mechanisms that can cause injury
  • Always pay attention to whats going on when working in the robot
  • Look out for others
    • Sometimes other students may be doing something unsafe or can lead to injury
    • Let them know, and/or the Safety lead, and/or a mentor

The End

Questions?

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