Notes

MOTION DEVICES
Must receive feedback about:
Displacement
Speed
Acceleration
Position

Forms ANALOG or DIGITAL

Analog can be resistance, voltage etc. Digital is 1 or 0, bytes etc.

Resolution
Smallest amount of movement required to detect to change.

Tachometer give output that is relative to a angular velocity.
USed in a wide range of speed related systems of systems. Most common being RPMS revs. per minute.

DC TachoMeter
Uses an arm connected in an electromagnetic system that when spun, will induce a voltage to produce a desirable output.
two types of DC tachometers
brush, brushless types.

V = k*B*(rpm)

... And the Toothed-Rotor Tachometer
Consists of a rotor with ferromagnetic teeth.
The rotor passes a solenoid and when close it will produce a stronger magnetic field. The reluctance is changing therefor the field grows.
Creates a pulse as output. Can be measured. They require an ADC to use the data mined from the meter.

Resolvers
Two windings 90 degrees apart.
One is sine and one is cosine. Knowing the angle each can give speed, direction and commutation feedback. These can indicate position between each point which makes it ideal for motors.

Inter changing the leads will cause changes to occur.
They are usually marked for clarity.
Keep in mind the frequency and magnitude of the voltage.
Advantage
Able to determine exact position or motor shaft
Not prone to dirty things.

Optical Encoders

Monitors direction of rotation, position or velocity
Optical rotary and linear encoders are the 2 kinds
More specific incremental or absolute encoders.

Four major elements
1. light source
2. light sensor
3. optical disc
4. signal conditioning circuitry of
As light passes it is either blocked or isnt, which gives a relative signal.

You can quadruple the resolution by increasing the amount of locations that you measure on the disk or rotating being used. Thus known as the quadrature encoder.
Based on the plot of A and B you can tell which way the machine is moving (left / right)
Absolute encoders look at very specific spots on something to tell positions. The data mined is digital. If you a have 5 tracks in total then you have
2^5 which is its positions per revolution. And you can find how many degrees you must move to go in one proportional revolution based on that one degree. 360/(2^(#of_tracks) gives degrees per rev
Gray code is insanely useful as it only changes one bit at a time which is good for error prevention.

Main advantages of absolute
Tolerant of supply failures. Can correct errors by cancelling out anomalies.

Accelerometer!
Measures acceleration forces. Like gravity, or vibrations. m/s^2
detects
vibration,shock,tilt, collision, acceleration. Very good for monitoring things that could possible collapse instantly. And for looking at the HP of a given machine.

LVDT
linear voltage differential transformer

A DC current is generated based on some sort of displacement in any way shape of form. Yes Mr. God you can do whatever you like. It uses induced voltage. Based on where the metal arm is, a different voltage is produced based on magnetism which creates a different magnitude voltage.
Hall Effect measure current flow.