Electronics Knowledge Compendium
From Team 449 Wiki
Though the Electronics subteam has only one major task to complete in order to have a working robot- building the electronics board- that job and the associated knowledge is very complex. This sort of knowledge cannot be learned in a day, but rather must come over time. In spite of this, a how-to guide and resource for the entirety of the electronics work of Team 449 will be immensely useful for quickly reviewing concepts and skills, as well as having a complete record of all of our general knowledge.
- 1 Planning the Board
- 2 Components
- 3 Crimping
- 4 Wires and Cables
- 5 Soldering
- 6 Batteries
- 7 Communication with Other Subteams
- 8 Competition Duties
Planning the Board
Before a board can be assembled, it must be planned carefully. Factors such as component accessibility, wire length and straining, and the surrounding parts of the robot are limitations that alter how the board can exist. Remember, the board has to be designed to accommodate the other parts of the robot, not the other way around.
Some elements of the electronics board have highly important roles such that, as will be detailed later, they must be easily accessible on the board. They cannot be covered, even by a piece that can be easily disconnected- they must be accessible at any time for any reason. These include the circuit breaker and certain parts of the roboRIO.
Main Article: Electronics board
The Electronics board is very much defined by the different parts that comprise it. Some parts are required, while others are situational. All of the major ones will be listed here.
Power Distribution Panel
Main Article: Power Distribution Panel
The Power Distribution Panel, or PDP, is akin to the heart of the electronics board. Many major components such as the roboRIO, Voltage Regulator Module, and Pneumatics Control Module are wired directly to this component, whose overall purpose is to supply power throughout the board.
Main Article: NI roboRIO
The roboRIO is the apparatus by which instructions programmed for the robot are transmitted electronically throughout.
Main Article: Circuit breaker
The circuit breaker is a precautionary device to stop the flow of current in case of danger. Unlike a fuse, which melts, a circuit breaker is a switch that can be reset after use. It is also used manually as a safe way of powering off the robot prior to disconnecting the battery. Due to its high importance with respect to safety, it is imperative
Main Article: Motor controller
These components control the speed of the associated motor by regulating the voltage it receives. Each motor controller has wires connecting it to the PDP and to motor it controls. There are two types of motor controllers we currently use- the Victor SP and the Talon SRX.
The Victor is a motor controller that transmits signals Pulse Width Modulation (PWM) wires, each connected directly to the roboRIO.
The Talon is a motor controller that transmits signals via Controller Area Network cables (which are green and yellow), allowing several Talons- that is, more than we would ever need to use- to be chained together. One Talon is connected to the CAN port on the PDP, and the Talon on the opposite end of the chain is connected to the CAN port on the roboRIO, while any other Talons are chained to 2 others.
Voltage Regulator Module
Main Article: Voltage Regulator Module
The voltage regulator module, or VRM, is a component that provides specially regulated power to components that take different levels of voltage and/or current, such as encoders and routers.
The VRM is powered by specially labeled ports on the PDP, taking up 2 out of the 6.
Pneumatics Control Module
Main Article: Pneumatics Control Module
The Pneumatics Control Module, or PCM, is a device that controls the electromechanical solenoids of our robot's pneumatics system, if applicable.
Robot Signal Light
Main Article: Robot Signal Light
The Robot Signal Light (RSL) is a simple yet crucial component that is wired directly to the roboRIO port labled "RSL". It blinks with varying intensity to indicate the current condition and competition mode of the robot. This information is absolutely imperative, and thus a robot must have a working RSL or it will not be permitted to participate.
Main Article: Radio
Crimping is, put simply, the act of joining pieces of metal by deforming both of them. We crimp wires to form a stable connection between them, the connection being called a crimp. Depending on the type of wires, different wire crimpers will be used.
Powerpole crimps are used for standard wires, and they have recently replaced the plastic crimps we formerly used due to their improved reliability.
PWM stands for Pulse Width Modulation, and is used to convert digital signals into analog ones by varying the frequency of pulses released to simulate varying voltage.
Wires and Cables
Main Article: Wires
Main Article: Wire Stripper
Stripping is the process of making a wire usable by removing a portion of the insulation. Knowing the wire's thickness, expressed in the AWG (American Wire Gauge) system is important to stripping it, as the wire should be placed in the correct sized hole of whichever stripper is used.
Wiring, the process of connecting wires, is the core of electronics work. Wiring occurs both within the electronics board and into the rest of the robot, such as the motors and pneumatics system. Wiring is a simple concept, but remembering what goes to where in every instance can be daunting, so there are a few tips for doing so that should be mentioned.
One of the easiest ways to wire correctly is to read. Because ports are usually labeled based on what is connected to them, it is difficult to make mistakes when reading. Additionally, because wires are color-coded based on what they do (power is red, ground is black, etc.), it can be easily understood that a red wire will always go into a port labeled with red (or a +). The electronics of the FRC is vast, but this is something that always holds true.
Main Article: Battery
The battery is the power supply for the entire robot, so maintaining functioning, stable, and properly charged batteries is an important responsibility carried by the electronics subteam.
When a battery is not in use and is below its maximum charge, it should be plugged in to charge.
In order to ensure that our robot remains powered before each match, we select the battery with the most remaining "life". Assuming nothing unexpected happens that requires maintenance, electronics only really has to worry about changing out the batteries between matches.
Main Article: Battery Beak
In order to ensure the proper battery selection, we use the battery beak, a device used for measuring the resistance and life of a battery. It is plugged into the battery in the same way that suicide cables would. "State of charge" is the name for the percentage of battery life there is, and so that is the main way to tell which battery should be used. This percentage can actually exceed 100, which, of course, is better. The internal resistance (RINT) is expressed both as a number and a representative word- Good, Fair, or Bad. If a battery is observed to be "Bad" and does not recover from this upon being charged, that battery should probably be put out of use.
Operating the battery beak is quite simple due to it only having one button. Pressing the button quickly moves the cursor while holding it longer makes a selection, allowing one to navigate to the appropriate menu. Evaluating the battery is the very first selection, so press for that.
Communication with Other Subteams
One major shortcoming in constructing the robot effectively is improper communication between the various subteams. Due to the role of electronics, there are many situations in which telling another subteam about what has been done- or what needs to be done- is very important.
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