Electrical Safety Basic Electrical Practices and Tips for

Electrical Safety Basic Electrical Practices and Tips for Passing Inspection George Mellors Teacher Engineering former Industrial Engineer

Agenda Electrical Safety (Hazards) Electrical Components System Design/Planning Resources Questions

Electrical Hazards 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.

Amps. vs. Injury in electricution 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.

Battery Safety 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

Battery Safety(continued) Do you have a Battery Spill Kit? ▪ WWW example ▪ http: //www. uline. com/Product/Detail/S-19486/Sorbents-and-Spill. Control/Battery-Acid-Spill. Kit? pricode=WY 233&utm_source=Bing&utm_medium=pla&utm_term=S 19486 Q&utm_campaign=Janitorial%2 BSupplies Do you have an emergency eye wash kit? ▪ WWW example ▪ http: //www. wayfairsupply. com/Sperian-Safety-Wear-Saline-Personal. Eyewash-Bottle-FND 320004520000 -L 2389 K~ZHK 1030. html? refid=MX 2649490155 ZHK 1030&device=c&ptid=1104000081468

Battery Current Overloads 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.

What happens with a Current Overloads (continued) 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 Safety Electrical Fire Class C fire extinguisher Battery Handling Gloves, Safety Glasses, clear path for transportation Battery Spill Response Connection Using FIRST connectors and proper wire gauge Tape, and more Tape… NO copper showing

Electrical Control System & Components

Robot (PLC) Rio, Robo Rio

Robo Rio (continued) 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

Victor 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

Motor Control Workhorses 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

Talon SRX Advantages CAN support Internal limit sensors Break/Coast Button Calibrate Button Disadvantages Connection/Application of 10 pin connector Wires are short. Challenge – Programming CAN

New Victor SP Advantages PWM control Break/Coast Button Calibrate Button Disadvantages No external input controls Wires are short. Would be used on simple control high amperage control.

Spike 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)

Control Table for Software Engineering Output from What does it control and how Special Considerations ▪ Servos (6 V) ▪ Speed Diagram if possible

What kind of control? ▪ CAN ▪ PWM ▪ On-Off ▪ Feedback ? If so from were ▪ Build in software ? ▪ Labels

Electrical System Design 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?

Electrical System Design 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 accessible ▪ Velcro panel, zip tied cover Radio should not be enclosed, keep from noise

Electrical System Design 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

Electrical System Design 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 Co. G

Inspection Tips 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

Acceptable Wire Gages

Common Inspection Failures Signal light properation + visibility Battery Terminal Lugs need electrical tape Voltage monitoring improperly wired Easily accessible 120 A breaker/Dump Valve

Other hints 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)

General Things 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 RIO!

Resources Usfirst. org Get the Inspection Checklist and FRC Suggestions Chiefdelphi. com Great forums for asking anything Andymark. biz Purchase electronics/gearboxes/chassis/misc Ifirobotics. com Purchase Victors/Spikes/Wheels

Thanks for attending! Questions?