In CNC Modulation is used to control devices remotely, or control the speed of Motors.
Below on this page the basics of Modulation and AC Induction Motors are covered.
FM (Frequency Modulation):
The Carrier Wave Amplitude remains constant but has a Frequency attached.
The Frequency is carried along the Carrier Wave, FM is more stable because as the Carrier wave is altered by wires, bridges, or overpasses, the Frequency carried by the Altered Carrier wave remains the same so the received signal remains the same.
AM (Amplitude Modulation):
The Carrier Wave is Modulated but the frequency of the wave remains at a constant.
EG: (Image below)
Signal = Carrier Wave.
AM = Amplitude Modulation.
The Carrier is Modulated itself, as the Carrier is altered by the environment (objects like wires and overpasses) the sound will change because the Frequency and Carrier change together.
To explain further, picture the AM part of the image below shrinking because the Signal wave shrunk, as you can guess the change results in a change at the receiver, if (for example) a Speaker moved as the peaks and valleys do (as shown in the Picture below “AM”), the shrunk Signal Wave will have more frequent peaks and valleys making the speaker move faster. In the case of FM, if the Signal Wave shrinks the frequency on the Signal Wave will remain constant, so the speaker will move the same with a shortened Signal Wave.
AC Motors and Frequency:
Most motors in the world that are AC (Alternating Current) operate at 50-60-Hz, this is how fast the Electrical Current changes direction every second at the wall too, in terms of your Lights, Laser on a Cutting CNC, Computer, Phone, or a Micro-processor, 50 – 60 times per second is slow, but it's what we get at the wall outlet in North America. Note: Take a look here: http://www.thingiverse.com/thing:1001437
In an AC motor you send power to the outer coils that make up the Stator, these coils are energized in pairs and in sequence to produce a temporary Magnet, this temporary Magnet repels or attracts the Magnetic Armature; as you know a Magnet has S (-) and N (+) poles, by energizing the Stator Coils in sequence the Armature moves (Rotates) in sequence (one direction).
PWM (Pulse Width Modulation):
Pulse-duration modulation (PDM):
VFD (Variable Frequency Drive):
By Modulating (Controlling) the Frequency power is turned on and supplied to an AC Motor, we can control Speed, and with speed control Torque, this is done using a VFD | Pulse Duration Modulation.
PWM Duty Cycle:
The amount of time the Power is turned on in terms of Percentage, Eg: %100 Duty Load = on full time or %50 Duty Load = on half of the time.
Side note: PWM is used for Data transfer too.
One | Two | & Three, Phase Motors are the most common.
With a single phase motor try to picture the Armature of the Motor with Four Sections, two Neg and two Pos sides opposed, as the current oscillates the Stator switches magnetic polarity in four parts and the Armature moves.
With two phases (Four Wires Two Posts): The Armature will have eight sections, and with a three phase motor (Six Wires Three Posts): The Armature will have twelve sections.
AC Inductance Motors are used for Power Generation. Look into Full-Bridge Rectification.
Getting it together:
Knowing this information we can now set something up that can control an AC/ DC / Stepper/ or Universal Motor using FM, we just need hardware and software.
Device (Wireless Transmitter and Software) -> Wireless receiver -> Micro Controller -> Motor Driver -> Motor.
Step-One: The Arduino sends a Signal using the attached FM Transmitter. A Computer connected to a Micro-Controller that has an FM Transmitter attached sends Commands to another Arduino with a Receiver.
An Arduino with an FM receiver receives the sent signal from the FM Transmitter, with the sent information we call a specific loop to control the Motor (Load), for example a signal “A” may result in a 10% Duty-Load.
With the signal and called Loop we set a specific I/O high this causes the Motor Driver to do it's thing.
The Motor Driver receives the signal from the Arduino and supplies power to the motor for the duration the I/O is set high, this is where the Motor Power Supply is connected, in a nutshell the Arduino and Motor Driver work as a very fast Switch supplying power to a Load as directed by the Computer.
Make it all Autonomous by adding Switches (Sensors) as Inputs to the same Arduino, on specific events have other Outputs set high to control other motors, actuators, lights, or sensors like cameras for example all with just one Arduino.