Download Electrical Safety Basic Electrical Practices and Tips for Passing

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George Mellors
Teacher Engineering former Industrial
Electrical Safety (Hazards)
Electrical Components
System Design/Planning
Battery Acid
Electron Flow Current
Short Circuit
 High current hazard
 Sparks
Electrical Fire(s)
 In competition, Moon rocks, a robot in the
Hartford competition was burned badly by an
electrical fire.
Note on right, it only takes 0.1 AMP
to 0.2 AMP for potential Death.
Batteries used in FIRST FRC
competition are sealed
Lead-Acid batteries. They can
produce a 50 AMP current.
Batteries used in FIRST Competition contain
Sulfuric Acid
 While handling, working, cleaning up from
accidental situations with a battery
 Wear Personal Protective Devices (PPD)
Safety Eyewear
Protective gloves, rated for battery acid
Apron, again rated for protection against battery acid
No jewelry which could conduct electricity
 Handling Upright and away from cloths and body
 Do you have a Battery Spill Kit?
▪ WWW example
 Do you have an emergency eye wash kit?
▪ WWW example
Commonly Called Short Circuits
 A short circuit occurs when the resistance in the
circuit is very low or zero.
 Using Ohm’s Law this results in very high current.
 It will be as high as the source allows.
▪ In San Francisco in 2001, a electrical repair crew on a sub
station North of the city energized the sub station
without removing the grounding strap. Put the entire
city in darkness until the issue was resolved.
Commonly Called Short Circuits
 How long is a short circuit?
Possible dangerous outcomes
 Sparks
 Current contact with, through, human body
 Overheat wires and electrical component(s)
Electrical Fire
 Class C fire extinguisher
Battery Handling
 Gloves, Safety Glasses, clear path for
Battery Spill Response
 Using FIRST connectors and proper wire gauge
Tape, Tape, and more Tape… NO copper
Robo RIO
 Powerful computer Control System
 Interfaces with control computer and robot system
 Programming
▪ Java, C++, Labview
 Module Order and placement matters
▪ Camera (x-over) = Port 1
▪ Radio = Port 2
Speed Controllers
 PWM Signal is sent to control motor speeds
 One controller per motor
 Two types exist:
▪ Victor 884 Jaguars (black new for 2010)
 Advantages
▪ In the program for a long time
▪ Easy to program
 Disadvantages
▪ Manual break/coast jumper
▪ Hard to calibrate
Black Jaguar
 Newer Technology
▪ Better low end control
 More features
▪ Read rules
 Unknown reliability
 Larger footprint
Victor 884
 Older technology
▪ Well tested
 Very reliable
 May be phased out in the
next couple of years
 CAN support
 Internal limit sensors
 Break/Coast Button
 Calibrate Button
 Connection/Application of 10 pin
 Wires are short.
Challenge – Programming CAN
 PWM control
 Break/Coast Button
 Calibrate Button
 No external input controls
 Wires are short.
Would be used on simple
control high amperage control.
Relay module
 Advantages
▪ Programmed easily
▪ On or Off only
▪ Outputs can be easily reversed
▪ Can control
▪ Compressor
▪ Solenoids for cylinders
▪ Small PM Motors
 Disadvantages
▪ Limited Amperage (fused)
Output from
 What does it control and how
 Special Considerations
▪ Servos (6V)
▪ Speed
 Diagram if possible
 What kind of control?
▪ On-Off
▪ Feedback ? If so from were
▪ Build in software ?
▪ Labels
Step 1
 Read the ENTIRE rulebook
 Think about the robot design
▪ How many motors?
▪ Which speed controllers?
▪ How many sensors?
▪ Safe wiring paths?
▪ How much space should be put aside?
▪ One board or multiple locations?
Step 2
 Discover how much space is allocated for the
electronics once the robot is designed
▪ Consider preparing an early schematic
 Electronics should be protected, but easily
▪ Velcro panel, zip tied cover
 Radio should not be enclosed, keep from noise
Step 3
 Get all components laid out nicely
▪ Non-conductive platform (wood/fiberglass/lexan)
▪ Think about wire paths (bend radius and #)
▪ Leave room in case you need to add something
 Try to group related components to shorten wires
▪ Use proper wiring color conventions
▪ Red/white/brown = Positive : Black/blue = Negative
 Labels!
▪ Assist troubleshooting and inspection
Step 4
 Bench top test the electronics if possible
▪ Basic control system & programming testing
 Mount into the robot when it is ready to move
 Secure wires from motors/sensors to frame
▪ Chassis must be isolated, no ground return
 Design a secure battery holder with quick access
▪ Remember, Battery position matters! Help your CoG
Do inspections regularly during build
 Know the rules!
Don’t crowd the inspector
 1-2 people interacting makes things easier
Neat wiring and accessibility
 Make sure all components are secured
Have charged battery ready + no air pressure
Signal light proper operation + visibility
Battery Terminal Lugs need electrical tape
Voltage monitoring improperly wired
Easily accessible 120A breaker/Dump Valve
Plan for sensor expandability
Keep a log of parts used
 Nice for keeping the budget for inspection
 Also keep a spec sheet of components for reference
With your log as reference you can form your own
schematic to assist in inspection/judging
 Schematics are great for debugging especially when those
who wired it aren’t around (off-seasons, future years)
Batteries, put someone in control of charging
Zip Tie/Velcro Anderson Battery connectors
during the matches
Assign someone to preventative maintenance
 Make sure zip-ties aren’t breaking, battery holder
loosening, etc
Check that your radio is plugged into the Robo
 Get the Inspection Checklist and FRC Suggestions
 Great forums for asking anything
 Purchase electronics/gearboxes/chassis/misc
 Purchase Victors/Spikes/Wheels