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Day 1
Summary of This Lesson
This lesson will go over how the pneumatics system works, which the electrical sub-team is responsible for. The lesson will go over what the different pneumatics components do, how they work with each other, and how to make pneumatics connections between those components. This page will essentially be for documentation, since Tinkercad does not feature pneumatics on their site. You would still need to read this to get a general understanding of how the pneumatics system works in FRC.
Lessons for Electrical Training on the website requires a Tinkercad account at www.Tinkercad.com, so if you haven't already, make an account on that website. Also, you can press the "Try Circuits" button in the circuits tab of Tinkercad to get an introduction of how to use Tinkercad's circuit simulation feature.
The Pneumatics Components
The last lesson went over these components:
Compressor: When activated through an electronic signal, the compressor pushes air into a reservoir.
Reservoir: Holds air.
Pneumatic solenoid: Uses magnetic fields generated by solenoids to move a metal rod forwards or backwards to block air from moving, or not block air from moving. Pneumatic solenoids are used with pneumatic cylinders.
Pneumatic cylinders: Uses air to extend or retract it's arm, called a shaft. Pneumatic cylinders extend or retract depending on where air enters into and exits from the cylinders
Pneumatic pressure switches: Used to tell the PCM (pneumatics control module) to turn off the compressor to stop pushing air into the reservoir when there is enough pressure.
We have a few more to introduce, which are the:
Pressure relief valve: Slows down the buildup of pressure (you don't want pressure to build up too fast).
Normal valves: Can be opened or closed to let air through or to block it. Can be used to quickly release the air from the system if one end is open to the air.
Pressure regulator: Takes in an unregulated pressure and outputs a regulated pressure (similar to a voltage regulator with voltage).
Pressure gauges: Used to measure the pressure where the gauge is at.
Compressor
Pneumatic reservoir
Pneumatic solenoid
Pneumatic piston
Pneumatic valve
Pneumatic pressure switch
Pneumatic pressure regulator
Pressure relief valve
Pneumatic pressure gauge
Parts for Connections
Having these components are nice, but we will also need to have a way to connect these components together. We have pneumatics tubing for that, but it is not as simple as pushing tubes into the components and having it stay like that. You might need a quick connect or hard fitting connector to connect components like a compressor to a reservoir. Anyways, here are the components used to make the connections between the components mentioned above.
Pneumatic tubing: Used to carry air to and from components. When cutting these, make sure the edges are 90 degrees! Jagged cuts are bad. This means that the end of the tubing is straight.
Quick connect connectors: Used to easily bridge pneumatics tubing together. For example, if a single pneumatics tubing path needs to split into to paths, you can use a push to connect connector to do that. You can also use that to simply connect two pieces of pneumatic tubing together.
Hard fittings: These are sort of like quick connect connectors, except you don't push to connect, you twist to connect. Hard fittings have threads on them, like a screw or bolt would. However, it is not as simple as just twisting components together and having them be connected. There are gaps in between the threads, so you need to go through one step before twirling your hard fitting. Simply take Teflon tape and wind it around the threads. Be sure to leave a little bit of space at the end of the thread (the space where the threads would first go into the other component) so that the threads can actually catch onto the other component's threads when you first start twisting. The Teflon tape is there to prevent air from leaking.
Pneumatic tubing
Hard fittings are the golden cylinders with threads. Quick connect connectors are the ones on the bottom right without a gold coloration
How it all comes Together
Storing air
In order to use air on our robot, we need to store it. We can use a pneumatics storage device to do that. One example is this: 574 ml Air Reservoir with Push Connect Fittings - AndyMark, Inc
Getting air into the reservoir
Now that we have some place to put the air, we need to get the air into the reservoir. We use a compressor to push air into the reservoir when it is powered. We can use a hard fitting (for the relief valve later) and a quick connect fitting after that. Then, we can use a pneumatic tube to connect the quick connect fitting to the reservoir. Be sure to wire the compressor to the PCM to power it.
Preventing a large increase in pressure
To prevent too much pressure increase, we will use a pressure relief valve, which we can connect to the hard fitting that was used right after the compressor.
Turning off the pressure when it's right
We can use a pressure switch to detect when the pressure is around 120 PSI, which is the right amount allowed by FRC. Be sure to wire this component to the PCM.
Knowing stored and working pressure
It is good, and also required, to know the pressure in the system. There are two different areas of pressure in a FRC pneumatic system. The first, being stored pressure. This is the pressure that the reservoir has. The other is working pressure. This is the pressure found "down stream", or after, the pressure regulator. This pressure is what is used by things like pneumatic solenoids or pneumatic cylinders. You would use a hard fitting paired with a quick connect to add it to the system. One gauge should be put after the regulator, and the other should be put before the regulator, and after the reservoir, since the pressure drops and becomes working pressure after the regulator.
Regulating pressure
Too much pressure can damage pneumatic solenoids or cylinders, so use a pressure regulator to lower the pressure. Place the solenoids and cylinders anywhere after the regulator. The regulator should be set to output a maximum of 60 PSI to comply with FRC regulations.
Having a way to purge air
When we want to get rid of the air stored, we can open up a valve to open the system up. This valve will need to be connected to a hard fitting, which can then be connected to a quick connect to connect to the system. Place this valve after the reservoir. Placing it after the regulator would mean air would purge slower. Generally, air would be purged after every match, since moisture in the air would stay in the system if the air is not purged for a while, which can create problems.
This picture is a good depiction of what the pneumatic connections would look like. This picture doesn't show the pneumatic solenoids or cylinders however.
Here is a pneumatics manual for FRC that can be useful throughout the build season: pneumatics-manual.pdf (windows.net).
It goes into detail of how to do things like calibrating a relief valve.
That's Pretty much it
The in-person people will get to put the pneumatics components together, power the compressor, and use the stored air to control solenoids to make cylinders extend and retract (and perhaps punch some wood with it).
Day 2
Summary of This Lesson
This lesson will cover how to power some FRC electrical components. Things like crimping and stripping wires and making connections with wago connectors will be included, as they are needed to make the connections in the first place. This will also go over the reasoning/how it works within the circuit. This lesson, and the next lesson, will only go over how components are powered and how to make connections that deliver the power to the components. These lessons are best taught in-person since members can do the wire stripping and crimping themselves to learn how to do those things.
Lessons for Electrical Training on the website requires a Tinkercad account at www.Tinkercad.com, so if you haven't already, make an account on that website. Also, you can press the "Try Circuits" button in the circuits tab of Tinkercad to get an introduction of how to use Tinkercad's circuit simulation feature.
Basic Handwork
To start off, we will go over basic hand work like stripping and crimping wires.
Stripping wires
Stripping wires is pretty simple. You take a wire stripper, like the one to the right, and you place the wire you want stripped in the slot with the same gauge number as the wires gauge. This is to make sure that the wire stripper won't cut too deep or too shallow into the wire. It should look similar to the picture below. How do you know how much wire you should strip off? It depends on the application. Usually, smaller diameter wires need less of the insulation stripped, while bigger diameter wires need more. This is because we use things called power poles that are meant to clamp onto the exposed copper part of the wire. Generally, if the wire is wider, the power pole's socket where the exposed copper goes into will also be wider, as well as longer. You want to fill that socket with the copper part of the wire to make a good connection.
Stripped wire
Power pole shell (left) and power pole (right).
Wire stripper
Crimping
Once you have a stripped wire, you can crimp power poles to the copper part. To do this, you take a crimper like the one on the right and you place the power pole into the correct slot on the crimper that corresponds to the gauge of the wire. Then, you place the exposed copper into the power pole and then you press the handles together. This makes the power pole latch onto the exposed copper, making a mechanical and electrical connection.
Using the crimped Power Pole
The power pole won't be left alone like that. It would be put inside a shell in order to link separate wires together. Simply put the crimped power pole end of the wire into the shell. Once you hear a click, it the power pole and the shell have latched onto each other. Now, you can take a wire with another power pole shell and power pole and push the power pole shell ends together to connect the two wires. This connection is not permanent, but at the same time, it is a reliable connection. This temporary yet reliable connection can be used for electrical connections that need to be connected and disconnected easily, perhaps for repairs, or changing components like changing the battery.
Additional note on Crimping
There is another thing that you can crimp to an exposed copper part of the wire, and that is a ferrule. A ferrule, like the one seen at the end of the wire on the right, is used to reinforce the copper end of the wire by wrapping a metal layer around the copper part. Crimping a ferrule onto a wire is similar to crimping a power pole. You take a ferrule crimper, like the one in the picture to the bottom right, then place the ferrule into the hole. Then, you can insert the copper end of the wire into that ferrule, then press the handles together. That will crimp the ferrule onto the copper end. You can use this in connectors called weidmuller connectors, which use a very tight clamping mechanism to hold onto wires. This very tight connection can occasionally cut the bare copper of a stripped wire, so we can use a ferrule to protect it, though it is fine to not use a ferrule as well.
Soldering
The last of the basic handwork involves soldering. Simply put, it is melting metal, called solder to make an electrical connection. Once the solder turns into a solid, it joins the two things you are trying to connect. Before you start soldering, you need to have the two things you want to connect together through soldering to actually touching each other. After that, you can have the solder in one hand, and the soldering iron in the other. Then, you press the soldering iron on the connection and slowly push the solder into that heated connection. Careful, as soldering irons are hot since it is made to melt solder. Take away the solder When the size and shape of the solder on the connection is right and leave the soldering iron for 1 more second then take it away. How do you know what size and shape the solder should be? It depends on what you are soldering. For soldering wires to other wires, it doesn't matter too much. As long as the wires won't come loose and that there is an electrical connection, it should be fine. For components with leads going into a PCB connection, it needs to form a smooth oval or cone like shape that isn't too big, like the one in the picture to the right. The left image in the picture shows how too big of a solder joint can bridge two electrical points together, which is bad, since it can cause a short or disrupt signals or current.
The Electrical Components for this Lesson
Here are the components that we'll be using for this lesson with their names, pictures, and short descriptions
12V Lead Acid Battery
This will be what powers all the electrical components on the robot, from powerful motors, to the roboRio.
120A Breaker
The 120A breaker is meant to disconnect the entire circuit from the battery if there is 120A of current coming from the battery. This is for safety reasons, as too much current can create too much heat, which can cause a fire. The 120A breaker has a black lever that extends out when the robot is off, and if you press it, it turns the circuit of the robot on. To turn the circuit, and in effect, the robot, off, you press the red button.
Power Distribution Panel (PDP)
This will be what distributes all the power to the electrical components on the robot. It has multiple ports for different purposes, like the large wago connectors for motor controllers, the smaller connectors at the end of the PDP to provide power to the roboRio, VRM, and PCM, and the CAN connectors to terminate CAN signals.
Motor Controllers
These are meant to be used to control the motors on the robot. There are various motor controllers that can be used with different motors, but they all have a the same purpose, to control motors.
Talon SRX Motor controller
Sparkmax motor controller
Motors
Motors are what make things move, specifically, rotate. These can be used in applications ranging from moving the entire robot, to moving a small arm. There are different motors like brushless and brushed motors, servo motors, and stepper motors. Each type has their own purpose, advantages, and disadvantages.
"CIM" motor, a brushed motor
Neo motor, a brushless motor
A typical servo motor
How the components are powered
As far as the components in this lesson go, it is not too hard to understand. We have the battery, 120A breaker, PDP, motors, and motor controllers. Below is a diagram of all the essential electrical connections on the robot which you can use to follow along.
The battery connects to the PDP, with a 120A breaker in-between in order for the power to be cut if there is too much current. Then, the motor controllers connect to the PDP side ports to receive the distributed power. Then, the motors connect to the other end of the motor controllers to receive the controlled power (which includes the current and direction) from the motor controllers. Essentially, the motor controllers take in the right amount of current and changes the direction of it to control the motor it is connected to in the way we want it to move.
How to make the Connections
Wire connections to the Battery
A battery doesn't come with it's own wires attached, so we will need to add our own. Typically we reuse previous year's battery which already have
wires, but we will still go over how to get a new battery ready for use. When working with batteries, BE AWARE OF THE TERMINALS! Safety first! Do not make any direct connections between the battery terminals, as the batteries can release a lot of current, resulting in a lot of heat. Work with one terminal at a time and be mindful of where wires are.
To do that, let's start with the wires that go to the battery themselves. The gauge of the wire should be 6 AWG or smaller (smaller number that is, meaning bigger wire diameter).
Have two wires, a black and a red 6 gauge AWG wire. Strip the ends of both of them so that the copper end is the same length as the depth of the hold of the power pole that is meant for 6 gauge AWG, as shown in the picture below.
Crimp those power poles onto the copper end using the crimper tool in the picture below, which can also be seen here: PRO-CRIMP Crimp Tool - AndyMark, Inc , and insert the red wire, for positive, into the positive side of the Anderson SB50 connector, which you can purchase here: SB50 APP Connector with Contacts - AndyMark, Inc, and do the same for the black negative wire.
Now that you have two wires, black a red, connected to the Anderson SB50 connector, we can focus on the other side. The other ends of the red and black wires should have lug connectors, which can be purchased here: 6 Gauge Compression Lug Connector 1/4 Stud Hole BURNDY #: YAZV6CTC14FX - AndyMark, Inc. Lug connectors are meant to make contact with the battery terminals.
Strip the unstripped ends of the red and black wires so that the copper ends are as long as the depth of the hole for the lug connections. Use the same crimping tool you used before, and crimp those lug connectors onto the wire.
Both the battery terminals and the lug connector have holes in them. Once you line the holes of the lug connector of the red wire to the red terminal of the battery and have them tightly touching, you can insert a screw that comes with the battery through both the holes.
The battery can also come with a nut and/or a split ring washer (used to make the connection tighter), you can put the split ring washer through the screw if you have it, and then the nut after. Tighten the nut so that the two terminals are very tightly secured.
Do the same for the lug connector of the black wire and the black terminal of the battery.
The connections between the lug nuts (which essentially is the rest of the circuit) and the battery terminals NEED to be very tight. Any movement of the lug connectors during a match can cause momentary "power outages" for the robot, which can last for a couple of seconds.
This is very important. Insulate the two terminal connections by having shrink tubing, which are hollow cylindrical pieces of rubber which can shrink when heated with a heat gun. If there is still metal showing near the battery terminal connections, top it off with electrical tape.
Anderson SB50 connector (right), and ~6 gauge AWG rated power pole.
PRO-CRIMP crimp tool made to crimp wide diameter wires like 6 gauge AWG wires.
Lug connector for 6 AWG gauge wire, used to make connections between the battery terminals and the wires attached to it.
Lug connector connected to a battery terminal. The black object to the right is an allen wrench.
Insulated battery terminal (no electrical tape needed as there isn't exposed metal).
Battery to PDP
Now that we have wires on the battery, we can start getting connections started. First off, we will make a connection to the PDP.
Since we don't want to have to constantly screw and unscrew the wires that we just connected to the battery to the PDP after every match in order to replace the battery, we will need to make another set of wires, red and black, that are connected to the SB50 connectors. So you would make a "mirror image" of the set of wires that are directly connected to the battery.
Once you have the other set of wires connected to an SB50 connector, we can work with it. DO NOT connect the other set of wires to the battery when working on the robot, like what we will be doing for the PDP.
Crimp the lug connectors, the same ones for the battery, to the new set of red and black 6 gauge AWG wires. Remember to strip the wire before doing that.
Using a 1/16” Allen wrench, remove the two screws securing the PDP terminal cover.
Using a 5 mm Allen wrench (3/16”), remove the negative (-) bolt and washer from the PDP and fasten the negative terminal of the battery connector.
Using a 7/16” (11 mm) box end wrench, remove the nut on the “Batt” side of the main breaker and secure the positive terminal of the battery connector
4. Secure one terminal lug to the end of the 6 AWG (16 mm^2) red wire. Using the 7/16” (11 mm) box end, remove the nut from the “AUX” side of the 120A main breaker and place the terminal over the stud. Loosely secure the nut (you may wish to remove it shortly to cut, strip, and crimp the other end of the wire). Measure out the length of wire required to reach the positive terminal of the PDP.
5. Cut, strip, and crimp the terminal to the 2nd end of the red 6 AWG (16 mm^2) wire.
6. Using the 7/16” (11 mm) box end, secure the wire to the “AUX” side of the 120A main breaker.
7. Using the 5 mm Allen wrench, secure the other end to the PDP positive terminal.
8. Using electrical tape, insulate the two connections to the 120A breaker. Also insulate any part of the PDP terminals which will be exposed when the cover is replaced. One method for insulating the main breaker connections is to wrap the stud and nut first, then use the tape wrapped around the terminal and wire to secure the tape.
9. Using the 1/16” Allen wrench, replace the PDP terminal cover
10. That was quite a bit, but thankfully, that is the last part of the lesson. These instructions were mainly for the in-person people, but having this on the website is still good for documentation.
PDP to Motor Controllers
The wire gauge you will use between the PDP and a motor controller depends on what motor the motor controller is controlling. For example, if the motor controller in question needs to power a motor that uses a lot of current to, for example, move the robot, you would want a thicker wire, or a lower gauge.
Thicker wires require larger holes. On the PDP, there are two sizes of holes, called wago connectors, for motor controllers. There are larger wago connectors that can take in 6-12 gauge AWG wire, and smaller wago connectors which can take in 10-24 gauge AWG wire.
Pick the wire gauge and wago size needed, then we can get to making the connections.
The motor controllers don't come with anderson power pole shells on them, so add those first like we did with the other wires.
Take the appropriately sized set of red and black wires and strip one end of each, which should expose 1/2 an inch of copper.
Attach anderson power pole shells onto them by first crimping on the power poles.
Strip the unstripped side of the wires to also have 1/2 inch of copper exposed.
Insert the copper ends of the wires into the wago connectors by inserting a screwdriver into the slot above the connector, lowering the handle end of the screwdriver, inserting the copper end of the wire into the hole (which got opened by lowering the handle end of the screwdriver), and releasing the screwdriver to have the internal clamp of the wago connector clamp onto the copper end of the wire. The red wire should go into the red hole, and the black wire should go into the black hole.
Take the anderson power pole shells from the wires you just worked with, and snap on the other anderson power pole shells from the motor controllers. Red goes to red, and black goes to black. This connects the motor controller to the PDP.
Top left is a Spark Max motor controller without anderson power pole shells at the ends of it's wire.
Motor Controllers to Motors
The process to connect the motor controller to the motor is similar to connecting the wago connectors from the PDP to the motor controller.
Strip the ends of the wires of the motor controller and crimp on the anderson power poles and put on anderson power pole shells on those.
Do the same for the wires on the motor.
The power pole shells should have the same color to the wire it is attached to for convention.
Connect the power hole shells together. Black goes to black, red goes to red. If there is a third color, connect the same color to the same color. This is to not mix up connecting a positive voltage to something that won't need that positive voltage for example.
That's basically it!
This meeting only went over how to make connections for the battery, 120 A breaker, PDP, motor controllers, and motors. The next lesson will go over how to make connections for the radio, roboRio, VRM, voltage converter, and the PCM.
For Referencing
You can reference this site: https://docs.wpilib.org/en/stable/docs/zero-to-robot/step-1/how-to-wire-a-robot.html to see how most of the electrical connections are made. This has a lot more detail such as how long the exposed copper should be for specific situations.
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