1. Electrical Layout and Construction Techniques for FRC
FRC 2587 Electrical Layout and Construction Guidelines Rev. 04

2. FRC 2587 Electrical Layout and Construction Guidelines Rev. 04
Overview
Electrical System
Major Electrical Components
Layout Guidelines
Construction Techniques
FRC 2587 Electrical Layout and Construction Guidelines Rev. 04

3. FRC 2587 Electrical Layout and Construction Guidelines Rev. 04
Electrical System
Example drawing provided by FIRST
Refer to FIRST web site (see “Resources” page)
Shows basic connection scheme with only a few of each type of sensor and actuator (motor controller, solenoid, relay, etc.)
Shows only one PDP, one VRM and one PCM. Will have to wait for new rules to know if multiples will be allowed.
FRC 2587 Electrical Layout and Construction Guidelines Rev. 04

4. Major Electrical Components
RoboRio
Power Distribution Panel
Voltage Regulator Module
Pneumatic Control Module
New Motor Controllers
RoboRio integrates the functions of the previous CRio, Digital Side Car and Analog Breakout Module and eliminates the big ribbon-cable between the CRio and the DSC.
The difficult to use WAGO connectors for the CRio power connections have been replaced.
All power connections now made with large and small spring (Weidmuller) clamp connectors only.
FRC 2587 Electrical Layout and Construction Guidelines Rev. 04

5. Major Electrical Components
RoboRio
Replaces Crio.
Different footprint with lower profile.
Enclosure is self-isolating.
Integrates functions of Digital Sidecar and Analog Breakout.
One piece design with fewer connections. No need for ribbon cable between CRio and DSC or separate Analog Breakout Module.
Numbering of ports is different from CRio; starts at 0 instead of 1. There may be minor software adjustments needed.
There does not appear to be any retention mechanism for connectors plugged into the PWM, DIO, Relay and Analog In ports. Users will most likely want to tie down these cables nearby to prevent them from disengaging due to vibration and tension.
It appears that it may be possible for conductive debris to collect in the connectors ports leading to shorting out of some of the signals. It would probably be best to cover the RoboRio when drilling metal nearby.
Need to watch out for stray strands shorting adjacent wires at CAN port connector and INPUT Power connector.
FRC 2587 Electrical Layout and Construction Guidelines Rev. 04

6. Major Electrical Components
Power Distribution Panel (PDP)
Replaces Power Distribution Board.
Slightly smaller footprint.
Able to read parameters via CAN Bus interface:
Temperature
System Voltage
Output Current per channel
Some teams have found that the lugs for the 12V input cables can only lay parallel to the long axis of the PDP and cannot be turned at an angle. Allow space for the crimp lug to protrude and for the bend radius of cables.
Allow about 1 inch on all sides (possibly more on side with 12V input) for wires/cable routing channel.
A small screwdriver, or similar tool, will be required to open the 40A and the 20A/30A terminals, like before.
The 10A and 20A terminals for the RoboRio, VRM and PCM do not require a tool to operate.
These terminals are very closely spaced. Some teams have found that wires that have been inserted into such terminals several times may develop “stray strands” that may intermittently short to adjacent terminals.
Current and voltage monitoring capabilities may be exploited to prevent brown out conditions and tripping of main circuit breaker. More sophisticated prioritized load-shedding software algorithms can be implemented to prevent brown-outs and tripping of the main breaker.
Need to watch out for stray strands shorting adjacent wires at CAN port connector and PCM, VRM and Controller Power connector.
Refer to Users Manual for specific instructions for connecting Input Power cables (available at Cross The Road Electronics web site).
FRC 2587 Electrical Layout and Construction Guidelines Rev. 04

7. Major Electrical Components
Voltage Regulator Module (VRM)
Replaces Converter module.
Provides regulated 12V and 5V for:
Wi-Fi Radio/Bridge
Camera (s)
Sensors
Other custom circuits
There are a pair of 12V outputs rated for a total of 0.5 Amps. There is another pair of 12V outputs rated for a total of 2 Amps. There are a pair of 5V outputs rated for a total of 0.5 Amps. There is another pair of 5V outputs rated for a total of 2 Amps.
One Beta Test team has found that the 12V output will not survive for very long when to the maximum of 2 Amps.
Allow about 1 inch on all sides for wire routing channels.
The terminals do not require a tool to operate.
These terminals are very closely spaced. Some Beta Test teams have found that wires that have been inserted into such terminals several times may develop “stray strands” that may intermittently short to adjacent terminals.
FRC 2587 Electrical Layout and Construction Guidelines Rev. 04

8. Major Electrical Components
Pneumatic Control Module (PCM)
Replaces Solenoid Breakout.
Can have multiple PCM’s in system.
Controlled by RoboRio via CAN Bus interface.
Powers compressor directly, Spike relay not needed.
The terminals do not require a tool to operate.
These terminals are very closely spaced. Some teams have found that wires that have been inserted into such terminals several times may develop “stray strands” that may intermittently short to adjacent terminals.
FRC 2587 Electrical Layout and Construction Guidelines Rev. 04

9. Major Electrical Components
New Motor Controllers
Can be used in place of existing Jaguar, Victor and Talon controllers.
More compact.
Integral input power and signal wires.
No fan needed and sealed against debris.
Victor SP
Use like Victor and Talon Controllers.
Talon
Use like Jaguar via CAN Bus interface.
Used to control motors using a PWM waveform to simulate different applied voltages.
The new motor controllers are not particularly vulnerable to conductive debris getting into them.
The input and output wires and the control wires are all soldered to the circuit board inside. It was not legal last year to change those wires.
Be careful when cutting the wires to length so they are not too short.
FRC 2587 Electrical Layout and Construction Guidelines Rev. 04

10. FRC 2587 Electrical Layout and Construction Guidelines Rev. 04
Layout Guidelines
Layout Considerations and Recommendations
Documentation
Examples
FRC 2587 Electrical Layout and Construction Guidelines Rev. 04

11. FRC 2587 Electrical Layout and Construction Guidelines Rev. 04
Layout Guidelines
Layout Considerations and Recommendations
Mechanical Constraints
Documentation
Power Flow
Signal Flow
Avoiding Electrical Noise/Interference
Manufacturability and Serviceability
Review and iterate
Based on many years of experience working in New Product Development, which is basically what FRC is
Up front planning, taking these considerations into account, will save a lot of time in the construction phase and give a more reliable result, saving very valuable time at competitions.
Your robot will look much nicer and be much easier to work on (construction, software integration, modification and repair).
FRC 2587 Electrical Layout and Construction Guidelines Rev. 04

12. FRC 2587 Electrical Layout and Construction Guidelines Rev. 04
Layout Guidelines
Mechanical Constraints
Allow sufficient space around components for wiring
Use pre-defined “wiring channels” between major components or groups of components
Locate control components away from sources of heat such as large motors and compressor
Eliminate sharp edges that may chafe through wire insulation
Locate Wi-Fi radio/bridge away from large metal parts in a protected area, preferably in the upper structure of the robot
Ensure that components such as the radio/bridge, RoboRio, PDP, VRM, PCM etc. are easily accessible to allow wiring work, modification, repair and verification by Robot Inspectors
These constraints are often in conflict with each other. Learning to resolve these conflicts is one of the major lessons learned in FRC.
FRC 2587 Electrical Layout and Construction Guidelines Rev. 04

13. FRC 2587 Electrical Layout and Construction Guidelines Rev. 04
Layout Guidelines
Documentation
Start with the documentation; connection tables or schematic drawing
Enables easy troubleshooting
Enables easy duplication (practice robot)
The documentation methods and tools for the electrical system can easily be adapted to document the pneumatic system
Best to use Google Docs or FIRST provided tools (SolidWorks Electrical or AutoCAD Electrical) that are optimized for electrical drawings
Assign names to wires in tables or schematic drawings
Makes troubleshooting much easier.
Can use sample layout provided by FIRST as a starting point.
Mechanical design should follow connection table or schematic drawing.
Use separate connection table or schematic drawing for documenting the power distribution scheme and a separate one for documenting the signal connection scheme. They would be confusing and difficult to use otherwise.
Can make template for electrical system before build season. It is almost certain that it will have to change but it will be more/less of the same.
Wire names assigned in connection table or on schematics can be applied during construction.
Dedicated electrical/electronic CAD tools.
These are optimized better for drawing schematics than Mechanical CAD programs but these take time to learn.
May have to make symbols for various components. Do this before build season.
FRC 2587 Electrical Layout and Construction Guidelines Rev. 04

14. FRC 2587 Electrical Layout and Construction Guidelines Rev. 04
Layout Guidelines
Power Flow
Follow current paths from the source (battery) to the load (RoboRio, camera, motors, etc.)
Prioritize minimizing the length of the power wiring
Refer to Game Manual to determine wire sizes and colours to use for each connection
Connections between battery, circuit breaker and PDP should use red and black 6 AWG, or larger, wire
Other connections between PDP and loads above 20 A should use red and black 12 AWG or 10 AWG wire
Other connections between PDP and loads of 20 A, or below should use red and black 18 AWG wire
Give priority to minimizing lengths of connections carrying the highest currents
Consider location of motor controllers; longer input wiring vs. longer motor wiring. Usually closer to PDP is best
Start with power flow drawing. The power wires are the largest and the hardest to run.
Power should only flow outward from PDP and should not “loop back”.
Where possible, locate motor controllers near PDP and keep wires between motor controller and PDP short, then connect to motor through longer wires.
Indicate wire sizes and colors to be used on the schematic.
FRC 2587 Electrical Layout and Construction Guidelines Rev. 04

15. FRC 2587 Electrical Layout and Construction Guidelines Rev. 04
Layout Guidelines
Signal Flow
Run signal wires of the same type together where possible (PWM, analog, relay control)
CAN Bus interface wiring is “daisy chained” from the RoboRio to each device in turn, ending at the PDP
Avoiding Electrical Noise/Interference
Avoid grouping signal wires with power wires and running them in parallel, keep them at least 2~3 inches apart
Acceptable for signal wires and power wires to cross at 90°
Try to keep power wires for motors circuits at least 3 inches away from RoboRio and radio/router
Indicate wire sizes and colors to be used on the schematic drawing.
Consider where connectors will be used and indicate them on the schematics drawing.
Wires smaller than 18 AWG are fragile and easy to break in FRC applications.
Wires larger than 16 AWG are bulky and harder to run nicely in robot.
Electrical noise can cause intermittent problems that are difficult and can take a lot of time to diagnose
Follow these rules-of-thumb to avoid possible problems
It is acceptable to group motor controller input wires with motor wires
FRC 2587 Electrical Layout and Construction Guidelines Rev. 04

16. FRC 2587 Electrical Layout and Construction Guidelines Rev. 04
Layout Guidelines
Manufacturability and Serviceability
Determine which components or subsystems will likely need to be serviced or repaired in normal usage
Simplify the design to minimize the need for direct access to verify proper operation
Where possible, use clear panels to allow easy visual inspection of as many systems as possible. Inspectors will appreciate this
Determine how much space would be necessary and the method of access for testing, repairing or replacing a component or sub-system
Where possible, avoid the need to remove other components or subsystems to gain access
Determine what tools would be necessary to gain access to the component or subsystem. Minimize the number of tools and fasteners needed to gain access
Make construction, troubleshooting, repair and modification much easier and less time consuming (sometimes makes it possible)
Avoid the need for many different types of tools and the need for unusual tools
It is easier to borrow common types of tools at a tournament
Avoid fasteners requiring small Allen keys – easy to strip out fastener and/or Allen key
FRC 2587 Electrical Layout and Construction Guidelines Rev. 04

17. FRC 2587 Electrical Layout and Construction Guidelines Rev. 04
Layout Guidelines
Review and Iterate
Review the design with other team members and mentors, taking into account the design objectives
Typically, the best designs have gone through 3~4 major iterations, each taking different approaches
Do one design, put it aside then do another design, taking a different approach.
Compare the various designs and take the best features from each to make final design.
Evaluate each design for criteria such as manufacturability, serviceability, wire lengths, signal/power separation.
This is good engineering practice.
FRC 2587 Electrical Layout and Construction Guidelines Rev. 04

18. FRC 2587 Electrical Layout and Construction Guidelines Rev. 04
Layout Guidelines
Examples
Octanis, the Good and the Bad
Standard Practice in Industry
The Ugly was in the drive train
FRC 2587 Electrical Layout and Construction Guidelines Rev. 04

19. FRC 2587 Electrical Layout and Construction Guidelines Rev. 04
Layout Guidelines
Octanis Electronic Panel, bottom view
FRC 2587 Electrical Layout and Construction Guidelines Rev. 04

20. FRC 2587 Electrical Layout and Construction Guidelines Rev. 04
Layout Guidelines
Octanis Electronic Panel, bottom view
Motor controllers lined up on each side of PDP so that connections between them can be short and direct.
Motor controllers connect to motors on same side, preferably.
Wiring channels on either side of the PDP, between motor controllers, used mostly for signal wires (PCM).
Battery wires from PDP and PWM cables exit electronics compartment through polycarbonate panel with de-burred holes to prevent chafing on metal panels.
Power wires from PDP, motor controller and Spike relays twisted together to reduce noise emissions.
Use ring-type crimp lugs on all motor controller power connections. These are much less likely to fall off the motor controllers.
Connections to loads made with Anderson connectors for ease of swapping motor controllers, Spike relays and motors.
FRC 2587 Electrical Layout and Construction Guidelines Rev. 04

21. FRC 2587 Electrical Layout and Construction Guidelines Rev. 04
Layout Guidelines
Octanis Electronic Panel, close-up view
DIO terminals
DIO cables
Digital I/O connection points are inaccessible on Digital Side Car
Don’t do it like this. Wiring to DIO terminals given too little space. These connections are difficult to build and service.
PWM cables for DIO strapped together neatly using small cable ties.
Wires from PDP to motor controllers have been kept as short as possible.
Made custom length PWM cables to minimize the “extra slack” and keep it neat.
FRC 2587 Electrical Layout and Construction Guidelines Rev. 04

22. Construction Techniques
Standard Practice in Industry
Use the correct materials
Use the correct tools for the task at hand
Use the tools correctly
Secure wires, with sufficient slack, to resist vibration and eliminate strain on connections
Wire labels, can also be used for pneumatic circuits
Verify the work, immediately after it is done is CRITICAL to your success on the playing field
The person doing the work checks their work, immediately
A second person checks the work afterward
A few minutes checking your work is much better than your robot sitting dead on the playing field.
FRC 2587 Electrical Layout and Construction Guidelines Rev. 04

23. Construction Techniques
Check wire size and color requirements in current rules
See “Resources” section for explanation of wire gauge sizes
Can use wires of larger size if connectors allow
For simplicity and ease of stocking, use 3 wire sizes plus PWM cables
Use 10 or 12 AWG for all power wiring (PDP to motor controllers/relays to motors)
Use 16 or 18 AWG wire in colors other than red and black for signal wires
Use 22 AWG wire for low current and signal circuits
Use twisted pair or shielded cable for analog sensor connections to avoid electrical noise/interference
2015 rules had a total of 5 wire sizes for different applications. Simplify to:
10 or 12 AWG for 30A and 40A circuits to and from motor controllers, Spike relays, etc.
16 AWG or 18 AWG for 20A circuits
22 AWG for other low current and signal circuits, i.e. CAN Bus, solenoid, sensors
26 AWG PWM cables/ribbon cables, smaller is more difficult to work with and more fragile but does not save much space or weigh
Wire sizes are typically printed along the length of the wire, along with a lot of other information
Twisted pair – about 1 twist in 1 inches for 18 AWG and larger, about 1 twist in ½ inch for smaller wire sizes
FRC 2587 Electrical Layout and Construction Guidelines Rev. 04

24. Construction Techniques
Use the correct tools for the task
Use the correct size and type screwdrivers to avoid stripping screw heads
Use the correct cutters for the wire size
for 18 AWG
and smaller
for 10 AWG
for 6 AWG
Incorrectly sized screwdrivers, larger or smaller, can strip the heads of the screws and damage screwdrivers
Using small, wire cutters on large wires (say 12AWG) can cause them to break and send parts flying.
See “Working With Wire” tutorial on Sparkfun website and FRC Code Orange videos on YouTube
FRC 2587 Electrical Layout and Construction Guidelines Rev. 04

25. Construction Techniques
Avoid using “adjustable” wire strippers
Will often be set for wrong wire size
Best to use “gauged” or “automatic” wire strippers
Avoids cutting too deep and cutting some of the conductor strands
Many can be set to strip a particular length of insulation off the wire
Easier to train team members to get good results and to be more productive and efficient
The “adjustable” wire strippers must be adjusted for each wire size to be used
Some automatic wire strippers will automatically adjust for the wire size. Have a knowledgeable person set it to cut through the insulation only, without damaging the conductors, and to strip the correct length.
FRC 2587 Electrical Layout and Construction Guidelines Rev. 04

26. Construction Techniques
Use correct “slot” in jaws to avoid damaging conductors
Start with properly stripped wire. Check each one, every time
insulation cut unevenly
conductor damaged
conductors cut unevenly
wire cut at angle
Make sure to choose “slot” corresponding to wire size when using gauged or automatic wire strippers.
Automatic wire stripper will close cutting jaws to cut insulation then grab wire and pull to remove a section of the insulation as the handles are squeezed.
Do not cut wire at an angle before stripping, for best results.
Damage to conductor can show up as areas with “copper color”.
Improperly stripped wire
Best to cut it off and start over
FRC 2587 Electrical Layout and Construction Guidelines Rev. 04

27. Construction Techniques
Use the correct lugs for the application
Use the correct size crimp lug for the wire
Red – for 22 ~ 18 AWG
Blue – for 16 ~ 14 AWG
Yellow – for 12 ~ 10 AWG
Use fork-lugs for terminals that already have screws installed, i.e. older motor controller types
Fold stripped wire back on itself several times if crimping lugs onto wire smaller than 22AWG. Otherwise, it will not hold.
Do not use crimp lugs with solid wire.
Use fork lugs so do not have to totally remove screws. Faster and reduces the chance of losing the screw. Some terminals have screws that are not meant to be removed.
FRC 2587 Electrical Layout and Construction Guidelines Rev. 04

28. Construction Techniques
Use ring lugs for connections where you install the screw
Up to two lugs can be installed on one terminal
Ring lugs prevent wire from falling off if the screw loosens.
Can install lugs back-to-back.
Installing lugs the same way up but offset – watch for clearance to adjacent circuits.
FRC 2587 Electrical Layout and Construction Guidelines Rev. 04

29. Construction Techniques
Use the correct (ratcheting) crimpers!!!
It is CRUCIAL to your teams success to do a pull test immediately after each and every crimp to ensure every one is good and reliably holds up over time
A different team member should do a pull test on every crimp afterward
for PWM cable contacts
for 6AWG
lug size color
code dots
for Anderson contacts
Do not use the 4-in-1 crimpers. It is difficult not to produce loose crimps, especially in inexperienced hands. They are cheap, $5 ~ $10. Put them away if you have one.
Ratcheting crimpers produce superior results with little training and practice but don’t cost much more.
Make sure you get ones for insulated terminals. Crimper for uninsulated lugs will not crimp insulated lugs properly. Test with scrap wire and a lug.
They are not very expensive ($15 at Harbor Freight – get two at this price, $30 at Fair Radio Sales, $20~$25 on Amazon, also auto parts stores)
Jaws of ratcheting crimpers are color coded to correspond to the lugs that they are meant to work on.
Learn how to release ratchet if wrong lug (too large) is inserted and it prevents the crimper from cycling fully
Use hydraulic crimper for 6AWG wires for battery-to-breaker-to-PDP connections ($55 at Harbor Freight), install 6AWG die and put the rest away somewhere safe
In a pinch, can use a large bench mounted vise to crimp the 6 AWG wires for the battery, breaker and PDP connections. Need to ensure that it still fits in the Anderson connector and the PDP.
Pull test done immediately after every crimp is crucial to reliable connections that are reliable over time.
This is standard industrial practice.
Doing pull test reduced wiring problems to 1 in two seasons (due to crimp on old battery cable) for DiscoBots
Do not recommend soldering connection after crimping. This practice is not supported by manufacturers of crimp lugs. This can lead to:
Damage to insulation on lug, especially if done by someone inexperienced with soldering.
Damage to insulation on wire, especially if done by someone inexperienced with soldering.
May not get proper penetration of solder into joint – nothing accomplished, time wasted.
Solder may get pulled up wire, by capillary action, past crimp lug causing a stiff section that ends abruptly. This leads to failure of the wire at the end of the stiff section when it is flexed repeatedly.
Use “Deluxe Crimping Tool” from Hansen Hobbies for crimping contacts for PWM cables. Link in “Resources” page contains link to video on how to use this tool.
Don’t need all tem members to know how to crimp PWM cables so train 2-3 students with good fine motor skills to do it.
FRC 2587 Electrical Layout and Construction Guidelines Rev. 04

30. Construction Techniques
0.5 ~ 1 mm longer than lug barrel
lug, insulation removed
Crimping wires properly
Ensure stripped section of the wire is the correct length
Put the lug into the crimping tool and squeeze tool 1 ~ 2 clicks
Insert wire and start squeezing until tool stops clicking and opens
Insert wire and start squeezing until tool stops clicking and opens
Lug with insulation removed to show how long stripped section needs to be.
Aim to make stripped section about 0.5 ~ 1.0 mm longer than the barrel of the crimp lug.
Put lug into crimping tool then squeeze closed one or two clicks to hold lug in jaws of tool
Must put lug in correct jaw set (match color code on lug to color code on tool) to get proper crimp.
Putting lug into jaw set meant for bigger lug – lug will not be sufficiently crimped and wire may pull out
Putting lug into jaw set meant for smaller lug – tool may jam and will have to be released manually
Ratcheting crimping tool will automatically open once fully cycled (closed completely)
Lug may stick in one of the jaws. Gently pull it out. Do not pull out by the wire.
FRC 2587 Electrical Layout and Construction Guidelines Rev. 04

31. Construction Techniques
Example of a good crimp
Examples of bad crimps
crimped areas
crimped on wire insulation
incomplete crimp
conductor too long
strands sticking out back of lug
exposed conductor
crimp misaligned
conductor too short
FRC 2587 Electrical Layout and Construction Guidelines Rev. 04

32. Construction Techniques
Labeling
Use peel and stick wire marker booklets or label printer
Soldering
Not needed often in FRC
Soldering is a manual skill that requires a lot of practice
See tutorial in “Resources” section
If a mentor or student knows how to solder, consider just having them do all the soldering
Get booklets of just numbers and alphanumeric wire markers
Use sharp tool to peel labels from booklet
Soldering probably requires more practice than practical in one FRC season to get good enough that one does not damage the wire and components being soldered.
FRC 2587 Electrical Layout and Construction Guidelines Rev. 04

33. FRC 2587 Electrical Layout and Construction Guidelines Rev. 04
Resources
American Wire Gauge (AWG)
WPI “Wiring the 2015 FRC Control System”
Sparkfun “Working With Wire” Tutorial
FRC 3476, Code Orange, “How To Crimp Wires For FRC” video
One Tesla, “The Basics of How to Solder” tutorial
Electronics Parts Outlet
Stocks many of the tools describe and linked on next pages
Offers discount on tools and parts to FRC teams
FRC 2587 Electrical Layout and Construction Guidelines Rev. 04

34. FRC 2587 Electrical Layout and Construction Guidelines Rev. 04
Resources
Wire marker booklets
Wire cutters for smaller wires, 26~18 AWG
Wire cutters for larger wires, 26 ~ 10 AWG
Cable cutter for 6 AWG wire
Automatic wire strippers
FRC 2587 Electrical Layout and Construction Guidelines Rev. 04

35. FRC 2587 Electrical Layout and Construction Guidelines Rev. 04
Resources
Crimpers for 22 to 10 AWG wires
Crimper for 6 AWG wires
Crimper for PWM cables and CAN wire connectors
Crimper for 15 A, 30 A & 45 A Anderson Powerpole contacts
Hemostat/forceps, “third hand”
FRC 2587 Electrical Layout and Construction Guidelines Rev. 04