Basic Terminology

• Terminology
• Must-Knows
• Tips
• Topology

Terminology

Basic Electrical Terminology

Volts (Power), V:

• The potential difference in charge between two points
• The size of the force that sends the electrons through a circuit

Amperes (Current), Amp, I

• The unit used to measure electric current
• The number of electrons flowing through a circuit. 
  

Watts, W

• A measure of the rate of energy transfer of an appliance
• The rate of energy generated or consumed
  

Ohms (Resistance), 𝝮

• A measure of the opposition to current flow in an electrical circuit

Circuit:

•  A closed loop of conductive material.
• Continuous flow of electric current. Positive to negative or ground. (+, -)

Series: 

• Components are chained together from positive to negative to positive, etc.

Parallel: 

• Negative to Negative and Positive to Positive

CANchain:

• The chain of CAN devices and their connections gives information to each other. Also referred to as CAN bus, there may be multiple for different parts of a robot.
• Electrically, the FRC CAN network is a two-wire bus, designed to allow dozens of devices to talk to each other with a single network. 
• Needs two 120-ohm resistors to terminate the ends of the bus.
  

Bandwidth:

• The ability to measure a signal

Multimeter: 

• Electronic measurement tool
• Used to measure various electrical values
• Analog vs Digital 

Must-Knows

FRC Electrical Must-Knows:

COMMON TERMS
TERM	DEFINITION
CAN	"CONTROL AREA NETWORK" A COMMUNICATION PROTOCOL USED BY DEVICES FOR BIDIRECTIONAL COMMUNICATION ON A CHAIN. COMMONLY FOUND AS A 22AWG GREEN AND YELLOW TWISTED PAIR. MUST BE TERMINATED USING 1200 RESISTOR BETWEEN HIGH AND LOW (YELLOW AND GREEN RESPECTIVELY)
PDH	"POWER DISTRIBUTION HUB" WHICH CONNECTS DIRECTLY TO BREAKER AND BATTERY AND DISTRIBUTES POWER. BREAKERS AND FUSES FOR OVERCURRENT PROTECTION. CONNECTS TO CAN FOR DIAGNOSTIC INFORMATION
ROBORIO	MAIN ROBOT COMPUTER
RSL	"ROBOT SIGNAL LIGHT" USED TO INDICATE STATUS OF ROBOT
VRM	VOLTAGE REGULATOR MODULE" USED TO SUPPLY SENSORS AND DEVICES WITH REGULATED 12V OR 5V POWER RATHER THAN RAW BATTERY VOLTAGE
PWM	"PULSE-WIDTH MODULATION" SIMPLE UNIDIRECTIONAL SIGNALING USED TO TRANSMIT A VALUE BETWEEN 0-100%
AWG	"AMERICAN WIRE GAUGE" AMERICAN STANDARD FOR WIRE DIAMETER. PRONOUNCED GAUGE. SMALLER NUMBER MEANS LARGER DIAMETER, DOUBLING WIRE DECREASES AWG BY 3
FUSE	OVERCURRENT PROTECTION DEVICE WITH COLORFUL PLASTIC HOUSING. PERMANANTLY DAMAGED WHEN TRIPPED
BREAKER	OVERCURRENT PROTECTION DEVICE WITH COLORFUL METAL HOUsING. AUTOMATiCALLY RESETS AFTER COOLING WHEN TRIPPED, TRIP INDICATED BY BLINKING LIGHT ON PDH
FALCON 500	BRUSHLESS MOTOR WITH BUILT IN MOTOR CONTROLLER. CONTROLLED OVER CAN
KRAKEN X60	NEWER BRUSHLESS MOTOR WITH BUILT IN MOTOR CONTROLLER. CONTROLLED OVER CAN, REPLACABLE LEADS
SPARK MAX	STANDALONE MOTOR CONTROLLER, COMPATIBLE WITH WIDE RANGE OF BRUSHED AND BRUSHLESS MOTORS

 

Tips

Tips:

• Generally, follow your subsystem leader before acting on anything.

• Have someone pull test your connections after you’ve done them, as it will save lots of times later.

• Work closely with the programming and mechanical subteams to make sure that what you’re doing aligns with team goals and mechanisms.

• Follow the safety guidelines mentioned in the section "What is Electrical?"

• Always sanity check.

• Always cross-check with leaders, resources, or mentors if you are stuck or unsure about anything.

• Have a system for batteries whilst in the pits to maximize organization, time, and battery output.
  

• Try and keep wire connections outside of hidden locations and easy to access if needed in a situation.

• Always make sure you have enough crimps, wire, and whatever you need before and/or during the season to prevent a shortage of what can be done.

• Be sure to mount your devices with actual mounts and not zipties if you can. Using zipties can be helpful if used properly.

Topology

Topology is a system of wire arrangement in which electrical components are connected together. There are different types that we can use in FRC.

The Daisy chain is when we use CAN wires to connect components one by one. They can either go linearly or in a ring, and remember CAN chains they MUST end in a terminating resister 

Benefits: Some of the benefits that come with using Daisy chains are that they have more organization and make it easier to make any fixes if needed. Wire management is also easily done with daisy chains. It is much to save space and avoid cluttering on the robots, which allows room for other important components.

Drawbacks: If one wire that may be closer to the beginning or middle ends of failing, the rest of the chain will fail causing many components to lose connections from each other. This can drastically cause our robot to fail in competitions, therefore it's crucial to pull test wires before installing them onto the robots.

Star topology is when there is a central point that all wires emerge from and connect to the rest of the electrical components. This method isn’t usually recommended. 

Benefits: If one motor loses connection, only that single motor will fail. The rest of the robot keeps running. Troubleshooting is much easier. If a device is throwing errors, you know exactly which port it belongs to. All CAN wires route back to one localized electronics belly pan. 

Cons/Drawbacks: CAN bus relies on high-speed signals. The electrical signals bounce back from the unterminated ends of the wires (called stubs), causing signal reflections and ringing. In FRC, the stubs must be kept under 12 inches long. A star topology will most likely fail because CAN runs at high frequencies and is highly sensitive to data reflections. If the PDH itself gets damaged, the whole thing shuts down. It requires more wire length, adding weight to the robot.

 

Think of the middle device as a PDH, many CANwires would go from the PDH and go out directly to separate components.