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Day 1
Summary of This Lesson
In this lesson, we will continue on with the last lesson by going over how to power more components. Since the last lesson went over basic hand work, this lesson won't go over those. If you haven't learned about basic hand work like wire stripping, crimping, etc., you can go to the last lesson in week 10, day 2. You will need to know those skills in order to progress with making any electrical connections. This lesson will specifically cover powering the roboRIo, radio, VRM, PCM, and the power converter. The lesson will also explain the purpose of each component within the larger robot circuit.
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.
Components in this Lesson
You will be working with the roboRio, VRM, PCM, radio, and the power converter. We will only focus on powering these in this lesson. The roboRIo is meant to control the robots actions through code and human input. The VRM regulates voltage for different components that require voltages that are not the same as the battery's voltage. The PCM controls pneumatic components which was discussed last week. The radio is meant to communicate between the drivers' hardware like a laptop, and the robot. The power converter is meant to provide additional cameras with the appropriate voltage. So, if the robot requires more than one camera, a power converter is needed to provide the additional cameras with the right voltage so that it can work well. All of these components need to be connected to the battery in one way or another. All of these components, except the radio, will be connected to the battery via the PDP. Technically, the radio connects to the VRM, which connects to the PDP, so the radio indirectly connects to the PDP.
Making the Electrical Connections
Powering the roboRio
Powering the roboRio is a simple job. This requires much smaller wire, around 16 - 24 gauge AWG wire. This powered connection uses Weidmuller connectors, which take in smaller wires, and require you to press down on a button when you want to insert or take out a wire. Many of the components in this lesson will use Weidmuller connections.
For the roboRio, take two 18 gauge AWG wire and strip both ends of the black and red wire so that 5/16ths of an inch of copper is showing. This length is to ensure that it isn't too long where the copper shows, but not too short where it won't make an electrical connection.
Next, insert one end of the red stripped wire into the PDP hole in the section "Vbat CONTROLLER PWR" by pressing down on the white button above to open the clamp, and letting go once it's in. The "Vbat CONTROLLER PWR" section provides power to the roboRio via the PDP. Do the same for the stripped black wire to allow the charge to return to ground/the negative side of the battery.
Unscrew the screws next to the power port on the roboRio to open up the clamps.
Take the other ends of the two wires, insert the red wire into the "V" section of the power port of the roboRio, and the black wire into the "C" section. "V" stands for the positive voltage, which is the positive side of the battery, and "C" stands for cathode, which returns the electricity to ground, or 0 volts.
After the two wires are inserted, take a small screwdriver and tighten the screws next to the power port.
There is an alternative way to connect wires to the PDP, and that's by using ferrules to reinforce the stripped wires.
Also, check that there is a red 10 amp fuse next to the "Vbat CONTROLLER PWR" section so that one, there is an electrical connection, and two, that there is a safety measure to prevent too much current. If there isn't one, search for a red 10 amp fuse used by the PDP and insert it into the empty slot.
That should be it for powering the roboRio.
Wires inserted into the "Vbat CONTROLLER PWR" slot (top image)
Wires inserted into the power port of the roboRio (bottom image).
Powering the VRM/PCM
The VRM and PCM both use the same section on for power on the PDP, which is the "Vbat VRM PCM PWR", which stands for voltage from the battery, used to power the VRM and/or PCM.
These steps to power the VRM or the PCM from the PDP are similar to powering the roboRio from the PDP.
Strip both ends of a red and black wire, generally 18 AWG gauge wire, to have 5/16ths of an inch of copper showing. Make sure the wire is long enough to reach between the PDP and the VRM/PCM
Have one red and one black wire be inserted into the "Vbat VRM PCM PWR" section into the correlating color, and since it's a Weidmuller connector, you need to press down on the white buttons above to open the clamps, insert the wire, and release the button to have the clamps latch on.
You should have a red wire go into a red port, and a black wire go into a black port.
On the other ends of the two wires, insert them into the "Vin" ports, which are also Weidmuller connectors, so you will need to press down on the white buttons to open the clamps, insert the wire, and release the button to have the clamps latch on.
Red wires should go to the red port, and black wires should go to the black port on either the VRM or PCM.
Make sure that the "Vbat VRM PCM PWR" section has a green 20 amp fuse next to it. If not, find one and place it in the empty slot.
That should be it. The process described above applies to both powering the VRM and PCM.
Connection between VRM and PDP
Connection between PCM and PDP
Powering the Radio
The radio can be powered in different ways. The first is through a power jack, though we don't normally use a power jack due to it's unreliability since it can get jostled loose. A better solution would be to use a POE (Power over Ethernet) Injector. This combines the power component and ethernet communication element into 1 wire that connects through an ethernet style port on the radio, hence the name, "Power over Ethernet Injector".
Take a Rev Robotics POE injector found here: POE Injector Cable - REV Robotics, and insert the male ethernet end of it into the 18-24v POE port on the radio.
Take the red and black power wires of the POE injector and insert it into the 12v/2A section of the VRM, red to red, black to black to have the right polarity. If it isn't stripped already, strip the wire so that there is around 5/16ths of an inch of copper showing. Optionally, you can crimp of ferrules to reinforce the exposed copper.
Take a normal ethernet cable, and make a connection to the female end of the POE injector. Take the unconnected side of the normal ethernet cable and make a connection with the roboRio's ethernet port.
Diagram of connections to power the radio.
Power wires of the POE injector cable connected to the 12V/2A section of the VRM. The male ethernet side of the cable goes into the 18-24v POE port on the radio.
The female ethernet side of the cable connects to an additional ethernet cable. That additional ethernet cable then connects to the ethernet port on the roboRio.
Powering the Power Converter
The power converter takes in 12 or 24v and outputs 5V with a maximum current of 5 amps. If you need to use additional cameras, so for example, two cameras instead of 1, you would use a power converter to power the additional camera.
Take the red and black wires and strip them if they are not stripped already. Have about 3/8 of an inch of exposed copper.
Insert the stripped red and black wires into a Wago connector on the PDP with a 20 A fuse.
The yellow wire and black wire next to the yellow wire is used to power the additional camera.
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.
Day 2
Summary of This Lesson
This lesson will cover how to make connections between components that deal with communication. Things like the CAN bus connections, DIO pins, and analog pins will be discussed. There is also discussion on how to wire encoders for use in measuring motor position and rotating direction.
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.
Wiring CAN bus connections
CAN (Controller Area Network) is used to control many different electronic components without needing to use too many wires. Instead of having a separate wire for each component going back to the roboRio, we can have components connect to other components, which would eventually go back to the roboRio. This means that the components are connected one after the other (so in series) with one end being the roboRio. The other end would be the PDP.
Devices that use CAN would be motor controllers like the Talon SRX, Pneumatics Control Module (PCM), roboRio for control, and PDP for ending the chain.
The order of the connections doesn't matter EXCEPT for the roboRio and the PDP. The roboRio and the PDP has to be at the ends of the chain, meaning you can have numerous orders of connection in the middle of the chain, but at the ends should be the roboRio and the PDP.
Now that you know the general "order" that the components should be connected in, we can get into basic handwork to make those connections, which is pretty simple.
The goal is just to be able to take a set of CAN wires from one component with CAN capability, and make an electrical connection with another component with the same capability.
There are different ways of doing this, but the team uses power poles and power pole shells which provides a reliable connection, but at the same time, is able to be disconnected easily when needed. This is similar to the Anderson Power Pole connections we make to power the components.
Strip the green and yellow CAN wires with the appropriate gauge option on the wire stripper (should be a small gauge wire, so around 20 gauge AWG).
Crimp on a molex microfit connector to the stripped copper. Then insert it into the shell that is for that connector. It should have an audible click when it is locked in place.
Once you have both the yellow and green wires inside the shell, you can use that to connect it to another set of wires with the matching shell.
Matching shell means that there is a male shell that connects to a female shell.
Make sure that green wires go to green wires, and yellow wires go to yellow wires.
Some CAN bus compatible components use weidmuller connectors to make connections. To connect the CAN bus chain to a component with that type of connector, you would either insert the stripped copper wires directly into the weidmuller connection hole or you can crimp on a ferrule to reinforce the stripped copper, and then insert it.
This is the process that you will use to connect CAN wires of any CAN bus compatible component to another CAN bus compatible component.
CAN connections between Talon SRXs and the PDP shown with yellow and green wires.
Molex crimper
Wiring Sensors
Each sensor has its own specifications that require it to be connected in various ways. Sensors can be digital or analog, like the ones we've worked with, which will require us to use the right port on the roboRio. Similar to the Arduino, we would connect a digital sensor to the digital port, and an analog sensor to the analog port. Another thing about sensors is that it can use a varying amount of pins. If a sensor has 3 pins for output and input, you would need to use three digital input/output pins on the roboRio.
The sensors will need a long enough wires to reach the pins on the roboRio. One way we can do that is through jumper wires; however, those wires can come loose easily.
A second way is to use small gauge wires that have the molex power poles and shells, similar to making CAN bus connections.
We will strip, crimp, and insert the wires into those molex power pole shells similar to how we would with CAN connections, and powered connections with the Anderson power pole connectors.
If we use what we've been using for things like powered connections and CAN bus connections, we will need to be mindful of how many holes our power pole shells would need to have.
We can use a molex power pole shell that has three holes. Notice how there are three columns of pins on the roboRio. This is why we will use molex power pole shells with three holes, since it will match up nicely.
The thing is, you don't need to use all the holes in the molex shell. You can just insert wires into the holes that the wires need to be in, and leave the extra holes alone.
On the roboRio, there are three columns, one for power, one for ground, and the last one for signal. Sensors that will require power would use 1 ground and 1 power pin.
As for the signal pins, if a sensor has two pins for signal, one for input and the other for output, you can use signal pins in different rows. Just use a molex power pole shell for the row that you want the other signal wire to be in and connect it so that the wire will connect with that signal pin, then leave the other holes alone.
Wiring Encoders
There are many different encoders that use different techniques in measuring rotation of motors. For these, there are specific instructions on the part documentation online that give you steps on how to wire different encoders.
Some encoders have wires that are soldered onto the breakout boards that connect the encoder to the pins on the Talon SRX motor controllers.
The breakout board has pins of it's own, which connects to the pins on the Talon SRX through a data cable.
Some encoders use 3.3v voltage, and others use 5v voltage. Look at the encoder's documentation to see what voltage it requires, then solder the voltage wire of the encoder to the corresponding pad for either 3.3 volts or 5 volts on the breakout board.
Solder the ground wire of the encoder to the ground pad on the breakout board.
The encoder then uses two wires that are used to transmit data about the rotation of the shaft of the motor. These wires are soldered onto the pads named A and B on the breakout board. If the wires have names that are A and B, then solder it to the same named pads. If not, then solder the wires in any order.
Talon SRX breakout board
Ribbon cable, a type of cable used to connect the pins on the breakout board to the pins on the Talon SRX.
Cautions
Smaller wires are more fragile as expected. However, people sometimes forget about that and so they remove a wire by pulling on the wire and not the wire housing itself (where the wires come in to). The result is this:
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