Embedded Files
Day 1
Summary of This Lesson
This lesson will go over how radios work, how they can send signals through electromagnetic waves, the radio used by the team, and how to power the radio. This lesson would generally only work for in-person people since there is no Tinkercad equivalent of the demonstration that is done in-person, but this page will still describe the demonstration.
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.
What is a Radio?
A radio is used to transmit and receive electromagnetic waves, specifically radio waves as you might've guessed. I won't go into depth between the different waves, but essentially, different waves have different energy levels, which can be indicated by the wavelength, or length between the top or bottom of a wave. The shorter the wavelength, the larger the energy. You don't really need to know this, but it is a good fact to know. Now how does it do this you might ask? Looking at the name of what it uses to transmit signals, electromagnetic waves, implies that it uses waves that comprises of electrical and magnetic components. You know that when you pass a current through a wire or inductor it creates a magnetic field. However, magnetic fields can also create electric currents by generating voltage.
Mini experiment
The in-person people will get to play around with some wires to simulate what a radio essentially does to transmit information using electromagnetic waves. What they will do is make a coil out of copper wire, then pass a current through it. They will put a straight wire next to it and measure the voltage across the ends, and they should see small voltages being created whenever current passes through the coil of wire. They will be asked what they think is causing the voltage, which would be the magnetic field from the coil. They will also get to experiment with putting more or less current (meaning there is more or less voltage supplied) through the coil and will get to see how the voltage increases or decreases across the straight wire as the current through the coil increases and decreases respectively.
How real radios create magnetic fields
After seeing how voltage in an unpowered wire can be created through current running through a coiled wire, they will get to know how a radios work in more detail. Essentially, radios have gradually changing current (and voltage) which creates a sine wave, like the picture to the right. The positive y values would represent positive voltage and current, while negative y values represent negative voltage and current. This creates a situation where the current is always changing, and radios need that to use different ways of communication and identification.
Different ways to communicate
Turning it on and off (pulse modulation): Having current run through the coil at one time and off at another (turning it on and off) is a simple way to communicate information. It can for example be used to communicate Morse code through the ons or offs.
Changing the amplitude: Changing the amplitude means to increase or decrease the difference between the peak to peak voltage, which means the distance between the highest and lowest voltage in the wave is changing. This can be used to transmit information like visuals in a TV or radio information like sound.
Changing the frequency: Changing the frequency involves making the cycles of the waves finish faster. A cycle of a wave means that the voltage goes to its peak positive voltage, to 0V, to its peak negative voltage, to 0V again. The picture on the right shows one cycle of a sine wave.
How radios identify different signals
The way that radios identify which signal is which is by looking for a specific frequency in a radio signal. So if a radio is looking for a radio signal with a frequency of 500 kHz, or 500,000 hertz, if it encounters a signal that completes around 500,000 cycles in one second, then it will pick it up and receive information that that signal has.
Here is a site that explains more about radios: How Radio Works | HowStuffWorks
Here is also a video that can explain how radios work:
Radio that the Team uses
The picture to the left is a radio that the team and other robotics teams use. Specifically, this radio is the Open Mesh OM5P-AC radio, which you can find here: FIRST Robotics Competition Radio Open-Mesh OM5P-AC - AndyMark, Inc . There are two options that you can use to power this radio. The first one is an older option, which involves plugging in the power and ethernet through separate cords. This can cause some issues since the power would go through a power jack, which in the past has caused unreliable connection since the robot jostles around, which can cause the power jack to also jostle around. The second method is by using a POE (Power over ethernet) injector cord.
POE Injector cord
A POE injector cord, like one that you can find here: POE Injector Cable - REV Robotics, is used to prevent the unreliable powering caused by the power jack by replacing it with a more secure connection. A POE injector cord essentially combines an ethernet connection and a power connection into one connection. To the left in the picture, you will see the part of the POE injector that goes into the "POE" port of the radio. The two wires, red and black, in the middle of the picture connect to the 12V 2A section of the VRM (voltage regulator module), which you may have worked with in a previous lesson. The part on the right of the picture is where a separate ethernet cable connects to, which the other end goes into the roboRio, making an ethernet connection between the roboRio and the radio.
The picture to the right depicts how a POE injector cable from REV robotics would be used with the VRM, radio, roboRio, and separate ethernet cord.
That's basically it
Sorry that this lesson on this page is bland, but unfortunately, there isn't a way to show how radios work using inductors and normal wire on Tinkercad. The in-person people will continue on to practice making a POE connection with the radio and playing around with inductors and wires to simulate radios transmitting and receiving signals.
Day 2
Summary of This Lesson
This lesson will overview what the PCM is, how it works with other pneumatic components, and how to wire it. This lesson won't go into too much detail of how pneumatics works, since that will be overview in the next lesson.
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.
Quick Overview of the Use of Pneumatics
Pneumatics on a robot means that the robot uses air to do things, like lifting itself up, or used in a clever way to rotate something heavy. This air is usually stored in a container, called a reservoir, which the air is gathered by the compressor. Different pneumatics devices like pneumatic cylinders are the ones that are pushing things, or retracting things depending on how the air flows inside of it. There are other components that help the air flow smoothly and correctly, which we will cover.
Some Quick Facts
In this lesson, there are some new components that will be mentioned. These components are pneumatic components, so you will need to get a quick introduction to those 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.
Compressor
Pneumatic reservoir
Pneumatic solenoid
Pneumatic piston
Pneumatic pressure switch
The PCM
The Pneumatics Control Module (PCM) logically would be used to control pneumatic components. The PCM has 4 different sections where you can make electrical connections. The first being the power section, which takes in 12V from the PCM section on the Power Distribution Panel (PDP). The PDP was covered in week 3. The pressure switch section has two connections that are able to be made, which doesn't care which wire connects to which connection. The compressor output section is meant to power the compressor (which is used to push air into something called a reservoir which holds air). The solenoid sections, called channels, are meant to trigger solenoids to allow air to move into or out of a pneumatic cylinder, which uses air to extend and retract it's arm, called a shaft. The CAN section is meant for a CAN bus connection to allow the roboRio to send commands to the PCM to do things like control solenoids or activate a compressor. Any colored markings, like the red and black for the power section or the solenoid channels, and the yellow and green markings for the CAN bus section means that the same colored wire connects to the same colored marking.
How it Works
The PCM is powered through its 12V connection, which connects to the PCM power section on the PDP. This power is used for both the compressor and the solenoids. When the PCM allows electricity to flow from the compressor output connection into the compressor itself, the compressor starts to force air into the reservoir. However, the compressor won't know when to stop, and if it continues to do that, the reservoir will have too much air inside it and will explode. The pressure switch, which connects to the pressure switch input connections, prevents the compressor from forcing too much air into the reservoir. The pressure switch is part of the pneumatic hosing network, and if it detects enough pounds per square inch (PSI) of pressure, it will tell the PCM to turn the compressor off. The solenoid channels are used to tell solenoids when and where air should flow to. These solenoids are connected to the reservoir on one side, and a pneumatic cylinder on the other. In order for the PCM to know what to do, like turn on the compressor, or when to activate a specific solenoid, it needs to be connected to the roboRio through a CAN bus connection/network, which is used to communicate between devices that have the CAN bus connections. There are a a couple more pneumatic components, but for this lesson, we will focus on the electrical side of things.
Side note
In the middle of the PCM, you will see 12V and 24V. There is a little piece of plastic and metal that makes connections between two of the three pins. The three pins are highlighted by a cyan color in the picture above. Looking at the 12V writing, the picture right next to it has a black rectangle encompassing the left and middle pins. The 24V writing has a rectangle that encompasses the middle and right pins. These show you what position the piece of plastic and metal should be to activate 12V or 24V. These are for solenoids that need 12V or 24V specifically. However, the 12V or 24V option will set all of the solenoid channels to 12V or 24V respectively.
SAFETY FIRST
Air might not seem like a dangerous thing, because after all, we breathe it. However, if you jam a lot of air into a small confined space, like a reservoir, it can become very spring-like, and if the confined space breaks due to the force that the packed air creates on the inside of the container, it can throw objects at you at very fast speeds.
Also, pressurized air can shoot into your skin and cause complications. Don't stick your hand in front of any area where there is air flying out of it, like a compressor.
You may know that there are machines that can be used to blow balloons and inflate them. The pneumatics compressor works in a similar way in that it forces air into something. You would not want to put your mouth in front of it, because like a balloon, your lungs expand, and can rupture. Rupture is just a nicer way of saying explode. Obviously, not good.
In general, know that you are dealing with pressure that can hurt you, so stay cautious, wear safety glasses, and you should be fine!
Not Much Else
Since there isn't a PCM equivalent on Tinkercad, you will have to watch these videos to see how the PCM works, as well as some additional info on pneumatics. The in-person people will get to connect wires and pneumatic components themselves. They will also get to play around with the compressor, pneumatic solenoids, and cylinders to see how they work.
Page updated
Google Sites
Report abuse