Title: Electrical Subsystem
1Electrical Subsystem
- Scot MarshallLead Manufacturing Test Engineer
Constellation Project / Orion CEV - Lockheed Martin Space Systems
- Michoud Operations
- Team 1913, Covington High School
- Covington, LA
- scot_at_LaFRC.org
- www.LaFRC.org
22006 IFI Hardware
3
6
5
9
9
4
5
2
8
1
7
32007 Version
4Power Distribution
This Schematic is available at http//www.ifirobot
ics.com/rc.shtml
5IFI Hardware
- Robot Controller
- Wireless RS-422 40-Channel Receiver
- Back-up 7.2 VDC Battery
- CM2 Camera
- Operator Interface
- Wireless RS-422 40-Channel Transmitter
- Power Supply
- Tether
- Power Distribution Panel
- Resettable Circuit Breaker (20A, 30A, 40A)
- Robot Controller Interface
- Cabling
- Serial Computer Interface
61. Operator Interface
- Inputs
- 12 VDC Power
- (4) Joystick
- Competition Port
- Team Number
- Radio Modem
- Outputs
- Radio Modem
- Dashboard (PC)
- Tether
- Special Instructions
- No external power needed when Robot is tethered
- Diagnostic Indictors for Robot and Operator
Interface
7Operator Interface
Competition
Tether
To PC Serial Port
Radio
Joystick
Joystick
Joystick
Joystick
Disable Channel
Robot Reset
Display Select
OI Reset
Team Number
This information is available at http//www.ifirob
otics.com/docs/oi-ref-guide-11-21-2005.pdf
82. Robot Controller
- Inputs
- Digital Signal
- Analog Signal
- Radio Modem
- Tether
- Serial
- Programming
- Outputs
- Relay
- PWM
- Radio Modem
- Special Instructions
- Use Breaker
- Wire ON when Robot is powered
- Use Backup battery also
9Robot Controller
Team Color
PWM Outputs
7.2 VDC Backup Battery
12 VDC Battery
12 VDC Battery
16 Analog Inputs
Program
Black Red Wh/Yel
Ground 5 VDC In/Out
Tether
Tether
18 Digital In/Out
Radio
Relay Outputs
Serial Input
Pgm
Reset
This information is available at http//www.ifirob
otics.com/docs/rc-ref-guide-01-31-2005.pdf
103. Breaker Panel
- Inputs
- 12 VDC from Battery
- Outputs
- Power Distribution
- Ground Plane
- Serial to Robot Controller
- Special Instructions
- Wire through Main Breaker
- Terminals Numbered
- G is Ground
- 40 is for 40A
- Wire straight into 40A (Drive Motors)
- Use Spade lugs for 30A 20A
11Breaker Panel
40A and 30A Breakers Installed
(6) 40A Breakers
40A wires attach under screw plate Power Ground
30A or 20A Circuits24 places
MainBattery12 VDC
Red/Green/OrangeStatus Indicator
PWM Cable
MainBatteryGround
Terminals use spade lugs
Reset
Serial to Robot Controller
124. Circuit Breakers and Fuses
40A
- Circuit Breakers
- 20A, 30A, 40A
- Push/Pull Installation
- Overcurrent (thermal) cutoff
- Resets as soon as condition is resolved
- Fuses
- 20A for Spike Relay
- One-time use
- Look for broken loop
- Same as for Automobile
30A
20A
Fuse Element
135. Wireless Modem (Transmitter)
- Inputs
- 9600 Baud RS-422 Data
- Outputs
- 902-928 MHz Band - 40 Channels
- Special Instructions
- 100-300 ft Range
- 35 Competition Channels
- Default (Practice) Channel 40
- 2 robots on Default will interfere
- 01, 04, 13, 22, 31 User Settable Channels
- Requires Robot Master Code Ver. 13
146. Victor 884 Speed Controller
- Inputs
- Digital PWM
- 12 VDC, Ground
- Outputs
- Variable Current
- Special Instructions
- Use 40A Breaker
- Use for CIM Drive Motor
- Wire fan ON when robot is powered
15Victor 884 Speed Controller
Fan GND Battery GND Battery 12 VDCFan 12
VDC
Motor GND Motor Power
PWM Cable Wh Rd Bk (Fits Poorly)
Red/Green/OrangeFwd/Rev/ActiveIndicator
Brake/CoastJumper
Cal
167. Spike Relay
Fuse
- Inputs
- Digital PWM
- 12 VDC, Ground
- Outputs
- Full Fwd
- Full Reverse
- Brake
- Special Instructions
- Use 20A Breaker
- Use for Motor Drive
Red/Green/Orange Fwd/Rev/ActiveIndicator
PWM Cable
178. CMUcam2 Camera Rev. A
- Inputs
- PWM Power from RC
- Outputs
- RS-232 DB9 to Computer
- RS-232 3-pin Serial to RC
- Servo Control
- Special Instructions
- Use PWM 7.2 VDC Supply
- Use for Motor Drive
- Connect Only 1 RS-232 at a time
18CMUcam2 Camera Rev. A
Servo Outputs Deleted
RS-232 to PC for GUI
RS-232 to Robot for Auto
PWM Cable Connector
Focus by Rotating
Red/GreenLED Indicators
RC Board Connector
On/Off
RC Power
This information is available at http//www.ifirob
otics.com/camera.shtmlCMUcam2_fe manual
199. Cables
- PWM Cable
- Digital Signal
- DB9
- Joysticks
- Serial Communications
- RS-232
- RS-422
- Tether
- Digital Signal Power
20Wires
- Wire Gage
- Main Power 6 AWG or larger (4 AWG)
- 40A 10 AWG
- 30A 12 AWG
- 20A 14 AWG
- Color Code
- Red/Blue - 12 VDC Power
- Black/Yellow Signal Return
- Green - Chassis Ground
- Safety
- Insulate all connections
21Documentation
- FIRST Robotics Website
- 2006 Manual The Robot
- IFIRobotics
- Robot Controller
- Operator Interface
- Breaker Panel
- RS-422 Modems
- Victor 884 Motor Controller
- Spike Relay
- Camera
22Robot Controller
- FRC Control System Overview(pdf) , Used for 2004
-2007 Robot ControllersInstallation Info (pdf)
Size and mounting infoFRC System Quick Start,
Used for 2004 -2007 Robot Controllers2005 -07
Reference Guide (pdf) 6-13-06, Used for 2005
-2007 Robot ControllerAnalog and Digital Input
(pdf) 2-17-05 schematicProgram Port Pin-out
(pdf) 4-7-05 schematic
23Operator Interface
- SpecificationsDescription2005 Reference Guide
(pdf) 11-21-05Installation Info (pdf)2004 FRC
System Quick Start (pdf)2004 FRC Control System
Overview (pdf)Competition Port Pinout Guide
(pdf) RevA 1-12-05Frequently Asked Questions
(FAQ)Legacy Docs
This information is available at http//www.ifirob
otics.com/oi.shtml
24Backup Charts
25Connectors
26Motors
27Compressor
- Inputs
- Digital Signal
- Outputs
- Air Pressure
- Special Instructions
- Use Breaker
- Wire ON when Robot is powered
- Need Pressure Relief
28Sensors
29Switches
30Chargers
- 7.2 VDC
- 1
- Main Battery
- 456
31Websites
- 7.2 VDC
- 1
- Main Battery
- 456
32Adapted from a 2004 Presentation
- Michael Dessingue
- College Mentor - Hudson Valley Community College
- mdessingue_at_nycap.rr.com
- Team 250
- Steve Shade
- Controls and Simulation Engineer Rolls-Royce
- steven.shade_at_rolls-royce.com
- Teams 1111 7
- Al Skierkiewicz
- Broadcast Engineer - WTTW-TV
- Askierkiewicz_at_networkchicago.com
- Team 111
33Overview
- Electrical kit and IFI Hardware
- Layout and Planning
- Resistance and Ohms Law
- Electrical Tools
- Myth-Busting
- Questions
34Documentation Example
35General Layout Tips
- Label and/or Color Code Everything
- Secure wire so a hit from another robot doesn't
stretch the wiring to a breaking point or pull a
terminal out of a breaker, victor or spike - When in doubt, insulate
- Secure the battery so it doesn't fall out
- Leave some slack in wire to allow for swapping of
parts - Be careful when running wiring through frame
members so that mech heads don't drill into it at
some point down the road
36FIRST Electrical Problem
- How much voltage is lost in a typical FIRST
circuit?
37Ohms Law
By Ohms Law V I R 12 V I 24 W I 0.5 A
_
12 VBattery
24 W
38Typical FIRST Circuit
120 A Circuit Breaker
Victor 884 Speed Controller
_
40 A Circuit Breaker
VoutMeasured
12 VBattery
Assuming the Victor 884 Speed Controller is given
an input signal of 254 from the Robot Controller,
how much voltage is output to the device?
39Typical 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
40More Wire Adds More Resistance
- Standard Wire Foot - A 10 gauge wire will drop
about 0.1 volt per foot at the stall current of
any of the drive motors. - There is resistance in every wire
- .001 ohm/ft 10 wire
- .0004 ohm/ft 6 wire
41Typical FIRST Circuit
- Resistances 8 6 0.0032 W 6 10
0.0060 W Rtotal 0.0092 W - Steady State Current 40 A
- Voltage Drop IR 40 A 0.0092 W 0.368
V - Max Voltage at Device 12V - 0.368V 11.632
V
42Typical FIRST Circuit
- Resistances 8 6 0.0032 W 6 10
0.0060 W Rtotal 0.0092 W - CIM Motor Stall Current 114 A
- Voltage Drop IR 114 A 0.0092 W 1.05
V - Max Voltage at Device 12V - 1.05V 10.95 V
- At Stall Current of CIM, Max Voltage at the CIM
motor for the same current path is 10.95V!
43Reducing Resistance
- Check every crimp to make sure the wires do not
move or turn when pulled - Use the correct tool for the job
- Solder all critical joints
- Shorten the length of your wires (also helps in
keeping things neat and traceable)
44Crimp Connections
- Buy a good crimper for about 20
- Home Depot, Lowes Electrical Sections
- Many Auto Parts Stores also stock crimpers
- Look for crimper with good handles and can used
with wire gauges 10 to 24
45Soldering
- Good Practice to solder all connections where
high currents exist - Use Appropriate Size iron for the job
- Use a Rosin Core Solder for all electronics
46Other Required Tools
- Multimeter (DMM)
- Voltage
- Resistance
- Continuity
- Wire Strippers
- Re-strip any wires where copper strands are lost
47Myth-Busting
48The RC, OI, Victors and Spikes need external
components to run (i.e. capacitors, voltage
regulators, etc.)
- IFI has done a good job of designing the power
and internal circuitry of all the kit electronic
components. There is no additional circuitry
required for reliable operation. The fan that is
mounted on the speed controller is required
though and most teams will wire this fan to the
controller power input. The fan then becomes an
indication of good input power to the controller.
49The controllers cant go from forward to reverse
quickly.
- The speed controllers do exactly what you tell
them to do. Your robot cannot make the sudden
changes you are demanding for other reasons
related to mechanical design and physics. You
cannot hope that the control system will overcome
all other losses. It does not have the power
resources to overcome the momentum of a charging
130 lb. robot and change its direction.
50The controllers and motors are not matched, the
switching is all wrong.
- This may seem to be the case, but the components
work very well together. All teams use the same
motors and drive components so there is no
disadvantage to any team using the supplied
parts.
51The OI says my battery voltage is 10.5 but my
voltmeter reads 12 at the battery. It must be
broken.
- Your RC voltage monitor accurately reads the
voltage that is present at its input. If your
RC reads 10.5 volts, there is considerable loss
in the wiring and connections. Check that you
have connected the RC to the 1 or 2 positions
on the breaker panel and check that your
connectors are well crimped and are tight and
fully engaged on the push on connections.
52(No Transcript)
53The battery is too small.
- The battery is actually very powerful. Most
teams have no problem driving a 130 pound robot
for more than two matches with the kit battery.
If your robot drains a charged battery by the end
of a match, the mechanical design is inefficient
or you are using some form of tank drive. (treads
or four or more non-steering drive wheels)
54TYPE ES18-12 CAPACITY 5HR 3.06A 15.3 AH 1HR
10.80A 10.8 AH 1C 18.0A 9.0 AH INTERNAL
RESISTANCE APPROX. 15m MAX. DISCHARGE CURRENT 230
A (5 SEC.) MAX. CHARGE CURRENT 5.34
55The main battery cannot be used lying down.
- The main battery can be used in any orientation,
including upside down. It can be charged in any
direction except upside down. Battery terminals
must be protected at all times and the battery
must be secured in the robot. You cant play
when your battery is lying on the field.
56A sparking motor is defective
- Sparks are normal in DC brush type motors. The
magnetic fields in a motor generate high voltages
that spark across gaps in the brush assembly.
Motors that are working hard or have worn brushes
produce more sparking.
57I can only get 11 volts at my motor running. The
breaker panel is defective.
- This actually is an effect of the some of the
principles discussed earlier. High currents in
the wires we use result in some voltage drop.
Measuring at the motor, is in effect,
compensating for this loss. Remember the wire
foot, every foot of 10 at stall drops 0.1 volts.
A one volt drop is an indication you have 10
wire feet of loss on the robot between the
battery and the motor. This could be two 10
gauge wires, five feet long, or four feet and a
speed controller or three feet, a speed
controller and a breaker and some connectors.
58The backup battery is disconnected when you power
off.
- According to the RC manual, Team LEDs (and the
backup circuit in the RC) will go out after four
seconds if the RC has not established contact
with an OI connected to the arena controller. If
an arena controller is connected and a link has
been established, the RC will shut down about
four minutes after main power has been removed.
The backup battery supplies current to the RC,
modem, servos and team LEDs when the main battery
has fallen below about 7.2 volts. You must hit
reset to save the backup.
59My Chalupa is only running a light load but it
keeps tripping the breaker, the breaker must be
defective.
- A current monitor would verify what the motor
current actually is. Many manufacturers make
clamp on probes that will monitor current for use
with you multimeter. If the motor current is high
check that there isnt a problem in the drive
system by running the robot with the wheels off
the ground. If motor current is normal, suspect
bearing side loads, misaligned wheels, etc. If
it is high, remove the motor from the
transmission and try again, if it is high suspect
a defective motor, if low, suspect a problem in
the transmission.
60I dont need to insulate the black wire
- The black wire carries the same current as the
red wire it is paired with. By insulating both
wires, you are backing up the backup. If the
insulation on a wire fails, the insulation on the
other wire keeps the electrical system safe.
(backup the backup is a common method used by
NASA and others to insure safety, reliability.)
The black wire on the motors are not connected to
battery negative all the time.
61Main circuit breaker is vibration sensitive it
needs to be shock mounted.
- This was true of the old panel type breaker, but
it is not true if the breaker supplied in your
kit this year or last. These breakers were
designed to be used in vehicles and boats. A few
have turned up this season that were sensitive to
light tapping on the red disconnect button.
These are defective breakers and should be
replaced.
62Protect the radio by putting it down inside the
robot.
- It is important to protect the radio modem and
the rubber antenna that sticks out the top. To
mount it down inside all of the metallic parts,
motors and transmissions, is reducing is ability
to communicate with the OI modem. The robot
modem needs to be mounted in a protected area
with the antenna vertical and as far from
metallic structures as possible.
63The antenna on the robot can be anywhere in any
orientation, same with the OI.
- Antenna coupling is greatest when the antennas
are mounted in the same orientation. Coupling is
minimum when the antennas are mounted 90 degrees
apart. The radios still appear to work but the
margin of good signal is vastly reduced.
64The IFI control system is awful, my robot keeps
cutting out.
- A robot that cuts out on the field is most often
a result of input power to the RC falling below 7
volts. A high current draw when running will
take the battery voltage down temporarily. The
RC will go to backup and shut down while the
input voltage is low. When it returns, the RC
will act normally. Occasionally a modem problem
may occur on the field, the IFI reps are
monitoring every robot and can tell most problems
from their monitoring station.
654 wire is way better than 6.
- This is partly true. If you are running a long
distance with the primary wiring and you can
stand the extra weight, then 4 gauge may be a
good choice. Mating 4 gauge to the Anderson
connector is a problem for most teams. For short
runs and the best weight savings, 6 gauge is
perfectly fine.
66Soldering is better than crimping.
- Manufacturers crimp contacts all the time and
the military requires crimping only. The big
difference is the crimp is made with a very
expensive crimp tool or by machine. For our
purposes, a soldered connection adds a little
insurance to the connection. A good soldered
joint is one that is mechanically sound to start
with. Crimp first, then solder, then insulate.
67A motor will run at free speed if you connect it
to a battery.
- The motor specifications are recorded under very
strict testing guidelines and using equipment
that takes away any variables in testing. The
motor may get you close to tested specifications
but dont expect to duplicate results in your
shop with a battery.
68The electrical rules dont meet electrical
practice. (NEC)
- The electrical rules attempt to follow NEC
guidelines if you check the open air tables.
This allows a 12 wire to be used in open air
where a 10 for the same current must be used in
conduit. I personally prefer to use 10 for all
high current wiring on the robot, and 18 for the
lower current valves and RC.
697. Battery connectors are too small, underrated.
- Although rated at 50 amps, the overall heat
generated in the connector during a two minute
match is low enough that teams do not need to
worry. If the connector is improperly crimped,
damaged or misaligned, or the robot design is
significantly inefficient, some heating of the
connector is possible and damage could be the
result. I have seen little evidence of connector
damage. Using alligator clips on the charger to
connect to the Anderson battery connector will
damage the surface.
706. The main battery cannot be used lying down.
- The main battery can be used in any orientation,
including upside down. It can be charged in any
direction except upside down. Battery terminals
must be protected at all times and the battery
must be secured in the robot. You cant play
when your battery is lying on the field. Also
dont pick up the battery by the wires, as
internal damage will result.
715. My four wheel drive robot eats batteries,
there is something wrong with control system.
- Four wheel or tank drive systems use incredible
amounts of current when turning using high
friction drive surfaces like belting or knobby
tires. When a robot turns it must drag the
wheels or treads sideways across the carpet. In
a tight or fast turn, this high friction
translates into near stall conditions for all the
drive motors. The result is temporary current
draw above 200 amps in a four motor drive. That
may be enough to draw the voltage in the battery
below RC minimum.
724. The backup battery is not used when the main
power is shut off.
- According to the RC manual, Team LEDs (and the
backup circuit in the RC) will shut down after
four seconds if the RC has not established
contact with an OI connected to the arena
controller. If an arena controller is connected
and a link has been established, the backup
battery will still be connected to everything on
the robot for up to four minutes after main power
has been removed. With servos and LEDs, a lot of
power is watsted. Press reset after every power
off.
733. The battery has memory and needs to be
discharged to zero.
- This is one of the most common myths. It arises
from a particular type of NiCad battery behavior.
Gel cell batteries do not have a memory that
needs any special handling. Charge them normally
with the supplied chargers and never at more than
6 amps.
742. The battery is too small.
- The battery is actually very powerful. Most
teams have no problem driving a 130 pound robot
for more than two matches with the kit battery.
If your robot drains a charged battery by the end
of a match, the mechanical design is inefficient
or you are using some form of tank drive. (treads
or four or more non-steering drive wheels). In a
hard match or a restart, you may not have enough
battery reserve to last two minutes.
751. You dont need to calibrate speed
controllers.
- The biggest myth of all. Do not believe this
one. The speed controller has the ability to
adapt to each joystick you use. Since each speed
controller is not matched to the joystick you
were shipped, they must be calibrated.
Calibration gives the controller the ability to
match the maximum travel on the joystick to the
maximum output on the controller.
76Planning Your Electrical System
- Plan, create drawings just like mechanical
systems - Create a test bed early
- Use test bed to test all systems before
integrating - Communicate effectively with the mechanical
sub-teams early and often - Document everything