First Robotics Introduction to Electrical Systems

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First RoboticsIntroduction to Electrical Systems

• Team UltravioletSouthwest High School
• MN SPLASH
• December 6, 2008

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How Do We Make Sense of This?
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Presentation Agenda

• Direct Current (DC) Basics
• Why Wiring Rules?
• First Robotics Electrical System Overview
• Electrical Safety
• Questions

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Direct Current (DC) Basics
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Bottom LineWhat Does the Robot Electrical System
Do?

• Stores Energy (Battery)
• Uses Stored Energy to Do Work (Motors, Solenoids,
  Etc.)
• Makes Decisions (Robot Controller)

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Whats Up With Voltage?

• Battery Stores Energy
• Volts Measures Pressure of the Stored Energy
• Volts Electrical Potential Energy

Water Pressure Height Electricity Pressure
Volts
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Whats Up With Current?

• Current Is Flow of Electrical Charges (Electrons)
• Current Flows Due to the Pressure of Voltage
• Current Flow Transports Electrical Energy

Water Flow Gallons Per Minute Current Flow
Amps (Amount of Electrical Charge Per Second)
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Whats Up With Resistance?

• Resistance is Restriction to Current Flow
• Volts, Resistance and Current have a Linear
  Relationship
• Ohms Law V I x R

Valve Closed Less Flow Valve Open More
Flow High Resistance Less Current Low
Resistance More Current
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What Happens to the Energy?
Moving Electrons Through Resistance Converts
Electrical Energy To Heat Energy Power is the
Amount of Energy Used Per Second
I
_
Electrical Power P V x I
V
R
V Voltage 12V I Current 0.5A R
Resistance 24 Ohms P Power 6 Watts
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Electric Energy Conversions

• Electric Energy to Mechanical Energy (The Robot)
• Electric Energy to Heat Energy
• Electric Energy to Light Energy

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Why Wiring Rules?
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Wiring Rules Provide For Electrical Safety

• Wire Size Rules
• Circuit Breaker Rules
• The Robot Must Pass Electrical Inspection

Wiring Rules Are The Electrical Codes for First
Robots
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Rules Designed to Protect Wires From Overheating
Wire Resistance

• All Wires Have Some Resistance
• Bigger Wire Less Resistance
• Smaller Wire More Resistance
• Current Through a Resistance Generates Heat
• So, High Current Melts Insulation, Causes Fires

12V -
I
Wire Resistance
Load Resistance
If Current is Too High The Wire Overheats
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Main Power Wires Carry More Current So They Are
Bigger
12V -
IT

• Battery Wire Current is the Sum of All Load
  Currents
• IT I1 I2 I3
• Use 6 AWG For Main Power Distribution Wires

IT
I1
I2
I3
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Battery With Big Wires
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Load Failures and Short Circuits Cause Excessive
Current
12V -
12V -
High Current
High Current
Load Failure
Short Circuit
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Circuit Breakers Open The Circuit On High Current
12V -

• 120 A Circuit Breaker - 6 AWG or Larger
• 40 A Circuit Breaker - 12 AWG or Larger
• 30 A Circuit Breaker - 14 AWG or Larger
• 20 A Circuit Breaker - 18 AWG or Larger

40 A
Circuit Breaker Opens If Current gt 40 Amps
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First Robotics Electrical System Overview
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First Robotics Uses a 12 VDC Electrical System

• Powered By 12V Battery
• Robotics Controller
• Robot Drive Motors Variable Speed, Reversible
• Robot Arms and Lifts Single Speed. Reversible
  if Needed
• Pneumatic Valves Solenoids
• Sensors

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First Battery and Battery Connector No
Substitutions
Battery
12V -
6 AWG
Battery Connector
6 AWG
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Main Circuit Breaker Ahead of All Loads
12V -
120 A
6 AWG
6 AWG
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Main Circuit Breaker Close-UP
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All Loads Fed From Main Power Distribution
Assembly
12V -
6 AWG
6 AWG
120 A

-
24V (For Controller)
Internal Electronics
12V (For WIFI)
5V (For Camera)

8 x 40A Breakers and Terminals
12 x 20-30A Breakers and Terminals
40 A
-
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Power Distribution Assembly Side View
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First Robotics Controller is the Robot Brain
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Robot Controller Connection ToPower Distribution
Assembly
12V -
6 AWG
6 AWG
120 A

-
24V
Internal Electronics
Controller Module
12V (For WIFI)
5V (For Camera)
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Robot Drive Uses Motor Speed Controller and Motor
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One Motor Per Circuit Breaker Circuit Breaker
Size Depends on Motor Load


PMW Cable To Robot Controller
40 A
-
-
Speed Controller
Output -
M
Power Distribution Assembly

-
Load
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Motor Controller Close-UP
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New Motor Controller Close Up
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Use a Spike Relay to Control Other Motors and
Miscellaneous Devices
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Spike Relay Close-Up
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Spike Relay Protected By 20 A Circuit Breaker (2
Non-Motor Loads)


PMW Cable To Robot Controller
20 A
-
-
M
Load
M-
Load
Spike Relay
Power Distribution Assembly
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Pneumatic Solenoid Close-Up
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Only One Motor Per Spike Relay


PMW Cable To Robot Controller
20 A
-
-
M
M-
M
Spike Relay
Power Distribution Assembly

-
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Electrical Safety
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Electrical Hazards

• Electric Shock
• Burns
• Stop Breathing
• Heart Fibrillation
• Fire, Explosion
• Burns
• Hazardous Fumes
• Tools
• Soldering Iron (Burns)
• Pliers and Wire Cutters (Pinches and Cuts)

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Precautions Against Electrical Hazards

• Never Work on the Robot With The Electrical
  System Powered
• Disconnect Battery (Best)
• Turn Off Main Circuit Breaker
• Avert Face and Body When Turning On Electrical
  System
• Wear Protective Equipment
• Eye Protection (Possibly Face Shield)
• Cotton Long-Sleeve, Long-Pants
• Leather Gloves (Possibly Insulating Gloves)
• Avoid Loose Clothing
• Remove Watches, Rings, Necklaces, Ear Rings and
  Other Jewelry

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Questions?