FIRST Electrical Subsystems

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FIRST Electrical Subsystems
Scott McLaughlin Kevin Taberski Team
1619 Up-A-Creek Robotics Longmont, Colorado

• Thanks to
• Michael Dessingue (Team 250)
• for the beginnings of this presentation.

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Overview

• Supplied Electronics Kit
• Innovation FIRST, Inc. (IFI) Hardware
• Layout and Planning
• Resistance and Ohms Law
• Electrical Tools
• Other Notes
• Questions

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Electronics Kit

• Batteries
• Charger
• Wires, Cables connectors
• Cooling fans
• Motors
• Sensors and Camera (?)
• IFI Robot Controller Items
• Joystick

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Electronics Kit
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(No Transcript)
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General Wiring Diagram
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Battery Notes

• Can work mounted on side
• Should last the entire match
• Mounting should be captive
• If 1st year, buy one extra
• Connectors will wear out, so use wire ties during
  a match
• Use extra connectors for charger
• Safety Can deliver tremendous amounts of
  instantaneous current, so all connections must be
  protectedup to switch and circuit panel

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Main Power Connections
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Battery Connectors
Be careful, as this previously supplied drawing
is misleading. The wire does not go under the
screw, it goes between the collar and the tab.
You may need extra smaller heat shrink and
electrical tape to make it all tight, neat and
safe
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IFI Hardwarehttp//www.ifirobotics.com/frc-robot-
control-system-overview.shtml
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Planning Your Electrical System

• Plan and get electronics running early
• Build test bed, and if possible make it the
  final-layout bread board so you have cabling
  ready for install
• Can also create mechanical drawings and
  schematics
• Think hard about the battery/cable placement
• Think about radio modem placement
• Use test bed to teach about system and test all
  subsystems before integrating
• Communicate effectively with the mechanical
  sub-teams early and often about wire runs,
  battery, interference from moving parts, cooling,
  etc.
• Label all wires, PWM controllers, sensors etc.

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CentralizedElectronics

• Pros
• Easy to layout
• Easy to work on
• Looks neat
• Easy to remove
• Cons
• Needs big open space on robot
• Might be harder to protect electronics
• Cosmetics?

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Final Electronics Testing
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Wire Labeling
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General Layout Tips

• Label and/or color code everything
• Secure wires (with some slack) so a hit from
  another robot doesn't stretch or break a wire or
  a connector
• If in doubt, insulate
• Be careful running wiring through frame so that
  someone doesnt drill into it, or the insulation
  wears

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Ohms Law
_
Ohms Law V I R 12 V I 24 W I 0.5 A
12 VBattery
24 W
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Example FIRST Circuit
120 A Circuit Breaker
Victor 884 Speed Controller
_
40 A Circuit Breaker
VoutMeasured
12 VBattery
Circuit consists of 8 of 6, 4 of 10, and 2
of 10. 14 Connections in the circuit
Ideal Value 12 V
Actual Value 0V to 11.63 V
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Crimp Connections

• Buy a good crimper for about 20
• Home Depot, Lowes, auto parts stores, Radio Shack
• Look for crimper with good handles and can used
  with wire gauges 10 to 24
• Consider double-action for more leverage (easier
  to us, but more expensive)

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Multifunction Crimper
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Wire Crimping Notes

• Use correct size wire and crimp connectors (check
  manual) 4 could be used for long runs but will
  be heavy
• Auto shops have finer strand wire than say Home
  Deport (much easier to work with) can also get
  very fine strand wire, but this may only make it
  harder to strip
• Have class on wire stripping crimpingbe
  prepared to use a lot of connectors and wires
  (but this will pay big dividends for the
  competition)
• Can solder connections, but a good solid crimp
  should sufficeif you need the extra assurance go
  ahead and solder, but will require extra tools,
  classes, time and skill to do it right

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Electrical Tools

• Multimeter (DMM)
• Voltage
• Resistance
• Continuity
• Hand Tools
• Wire Strippers
• Crimpers
• Side-cutters
• Needle-nose
• Screwdrivers
• Oscilloscope
• For some demonstration and testing of items such
  as sensors

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More Battery Notes

• Backup battery can discharge if RC link is
  established
• If your battery is not lasting long, note that
  tank-drive and 4-wheel drive can use lots of
  current also check for high loss connections
• Check battery connections throughout season. A
  short can quickly heat up and start a fire or
  burn somebody. The battery voltage is not really
  dangerous, but the current is!!!
• Dont drop the battery!, and if the internal
  connections are loose, stop using the battery
• Label batteries for reference

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Motor Notes

• Motors can get hotbut usually only during long
  practice sessions. Allow them to cool down if you
  can not put your hand on them for a few seconds.
• Supplied wires on CIMs seem too small, but since
  they are short, is not really a problem. You will
  use larger gauge up to these..
• Consider using quick disconnects (spade lugs) for
  motor leads
• Not all identical motors are the same, and
  there is also directional biaskeep this in mind
  for autonomous modes
• Internal sparks are normal and increase as the
  brushes wear out

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Controller Notes

• Most problems are
• Low battery voltage
• Poor connections
• Not knowing how to setup the controller properly
• Radio Frequency Interference
• Understand simultaneous operation of multiple
  robots (i.e., Team Number Switches)
• Robot-mounted radio modem should be reasonable
  clear of metal, wires, and stuff.
• Mount robot controller for easy accessibility for
  serial cable and view of LEDs
• Of course main breaker should have easy access

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Sensor Notes

• We have not used that many, yet
• Most used have been limit switches
• Plan for and test early, both for electrical
  installation and for controller programming
• Very important for autonomous mode
• Harder to teach, implement and debug (be careful
  not to make things too complicated)
• Can be mechanically tricky to mount properly

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Remember

• They have not given you enough time
• They have given you too much to too
• They have given you too much stuff
• Fast, cheap, good (pick one!)
• All team members are responsible for safety
• Have fun, and remember it is for the kids-)
• Good Luck..

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Thanks
Team 1619, 2006 Season