Negative Feedback

We just learned about the Encoder.

Another part of a servo is Negative Feedback.

When a servo machine is working, and it needs to tell the motor to STOP, it needs some sort of a sensor that tells it when to stop.

A negative feedback part of a machine is something that senses when something gets to a point where it needs to stop, and the movement of the machine stops the machine itself.

That might sound sort of confusing, but if you think about a real world example it makes sense.

In a toilet there is usually a type of ball that is floating in the water in the tank.
When there is no water, the ball is hanging down, which lets the water flow in to fill up the tank.
As the water starts to rise, it gets to the ball and starts to make it float.
When it gets high enough, the ball is floating and it is connected to a valve that closes to stop water coming in.

So the ball floating is the negative feedback saying CLOSE THE VALVE AND STOP LETTING WATER IN, and the more the ball floats up the more the valve closes until it is totally closed and the water stops coming in.


(from: wikipedia - negative feedback)


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Encoder

We just learned about the Servo, that has sensors to tell it when to start or stop.

One part of a servo is the Encoder.

An encoder is like a map that the servo uses, so when the machine moves it knows where it is and when to stop.
Encoders have markings on them that a sensor can see to tell the machine that it is moving.

A rotary encoder is a type of encoder for a machine that spins.
It has lines on it to help the machine figure out how far it spins around.
If a machine spins to the right, the sensor might see 10 black lines go by.
The machine would then know that if it wanted to go back to where it started, it could spin the other way until it counted 10 black lines go by.


(from: wikipedia - rotary encoder)


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Servo

We just learned about the Valve Types.

Another part of machines is a Servo, also called a servomechanism.

This is something that uses special sensors to make a machine move or stop moving if it senses something bad.

When you go to a store and the automatic door is closing but senses you walking through it and stops, that is using a servo.
The servo has a motor that is closing the door, and then the sensor tells it that there is someone there, and it tells the motor to stop.

When it is clear, the servo tells it to close the door.

So a servo is really like a smart machine controller that automatically turns on or off when it needs to.


(from: wikipedia - servomechanism)


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Poppet Valve

We just learned about the Ball Valve.

Another type of valve is the Poppet Valve.

This is a valve that is usually used to open and close for gas to come through.

In a car's engine there are valves used to help the fuel come in, and after it makes a big explosion there are valves to let the burnt up air out.



(from: wikipedia - poppet valve)


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Ball Valve

We just learned about the Valve Trim.

There are a lot of different kinds of valves.
One type of valve that is used a lot is the Ball Valve.

It's called a ball valve because inside the valve there is a ball.
The ball has a hole in the middle of it, and the valve handle turns the ball.
When the ball is turned one way, the water or gas can go through the hole in the ball.
When the ball is turned the other way, the ball blocks the water or gas, and keeps the valve closed.



(from: wikipedia - ball valve)


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Valve Trim

We just learned about the Valve Spring.

Another part of the valve is the Valve Trim.

The valve stem, seat, disc and any parts that are inside the valve are all together called the Valve Trim.


(from: wikipedia - valve)


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Valve Spring

We just learned about the Gasket that helps keep a valve from leaking.

Another part of a valve is the Valve Spring.

Some valves use a spring to keep a valve closed, but if there is a lot of pressure they will squeeze and let the disc open and let some pressure out.
Once enough pressure is let out, the spring will push the disc closed again.


(from: wikipedia - relief valve)


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Gasket

We just learned about the Valve Stem that sticks up from the valve.

Another part of a valve is the Gasket.

This is a small circle that goes inside any place where two pieces of a valve have to be connected.
So at the top where the bonnet goes is sometimes a gasket, and then where the ports connect to other pipes is sometimes a gasket.

It's a way to help make sure that the liquid or gas doesn't leak out through where the two parts are connected.

Sometimes they're made out of rubber, but other times they're made out of paper or even metal.


(from: wikipedia - gasket)


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Valve Stem

We just learned about the Valve Seat.

Another part of a valve is the Valve Stem.

This is the part that sticks up out of the valve, and is used to help open and close the valve disc which lets gas or water go or stop.

There is a valve stem on a bicycle tire that sticks out.
If you hook a pump up to the valve stem, it will push in a pin which will allow air to go in or come out.


(from: wikipedia - valve stem)


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Valve Seat

We just learned about the Valve Disc.

Another part of a valve is the Valve Seat.

We know that the holes where the water or gas come in are the ports, and that the part of the valve that closes those holes is the disc.
The part of the valve that touches the disc and makes it a tight seal so nothing can get through is called the seat.


(from: wikipedia - valve)


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Valve Disc

We just learned about the Valve Handle.

Another part of the valve is the Valve Disc.

Inside the valve body is the part that moves to open or close to control the water or gas coming through.

There are a lot of different types of discs, that move in different ways to open up and close.


(from: wikipedia - valve)


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Valve Handle

We just learned about the Valve Port.

Another part of a valve is the Valve Handle.

To open or close a valve, you can turn the handle one way or another.
This is just like the faucet that you use on a sink or a water valve outside the house.

There are a lot of types of valve handles.
The one on the faucet outside the house is usually a wheel handle that spins around.
The handle on the sink faucet is usually some kind of lever handle.
The handle underneath the sink that connects to the water line is usually a T shaped handle.

Some valves don't have handles because they are automatically opened by some other type of machine.


(from: wikipedia - valve)


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Valve Port

We just learned about the valve Bonnet.

Another part of a valve is the Valve Port.

This is the part of the valve that lets water or gas in or out.
They can have as little as just two ports, but many valves have more.
Some valves even have up to 20 ports!

Simple two port valves are just open or closed.
Other valves with a lot of ports might have a few open and others closed depending on how it is set up.


(from: wikipedia - valve)


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Bonnet

We just learned about the Valve Body.

Another part of a valve is the Bonnet.

This is on top of the valve body, covering up the inside of it.
The bonnet can be taken off the top to open up the valve and fix it.


(from: wikipedia - valve)


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Valve Body

We just learned about the Valve.

There are a lot of parts to a valve that make it work.
Most of the parts of the valve inside of it that you can't see are all together called the Valve Body.

Inside the valve body are the parts of the valve that open and close to let gas or liquid through.


(from: wikipedia - valve)


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Valve

We just learned about the Cam.

Another part of moving things like machines is a Valve.

This is something that opens and closes to let air or water in or out.
We use valves every day, like when we turn on the water to wash hands.

Turning the water on opens the valve, and you can usually open it a little or a lot.
Then turning the water off closes the valve.


(from: wikipedia - valve)


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Cam

We just learned about the linear actuator.

Another type of actuator or moving machine is a Cam.

A cam is a disc usually on a rotor that is spinning around.
The disc is mostly shaped like a circle, but it as a part that sticks out like a bump.
The circle disc is called the camp plate, disc cam or radial cam.

When the rotor spins around, that bump part of the cam can push down on something like a shaft or a pole.
Machines can use this to push those shafts down over and over again.
So every time the rotor spins around, it pushes the shaft down and then back up.


(from: wikipedia - cam)


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Linear Actuator

We just learned about the Rack and Pinion gears.

Another type of thing used in machines is a Linear Actuator.

The word actuator really just means "mover" and there are lots of types of actuators out there.
Linear means moving in a straight line.

So a linear actuator is a type of machine that moves something in a straight line.
We learned before about rotors that spin around in circles in electric motors.
So this is different because it might be moving a rod up or down, back or forward but in a straight line.

Sometimes this is done by having a bolt or screw that has lines on it, and then a nut spinning around on the screw that makes the screw go up and down.
This is a roller screw linear actuator.


(from: wikipedia - linear actuator)


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Rack and Pinion

We just learned about the Air Gap in a motor.

Another type of thing used in machines is the Rack and Pinion.

A pinion is a gear, which we learned is a circle with teeth on the end.
The rack is a long flat line that has teeth on it, that match up with the gear.

When the gear spins around, it goes along the rack one way or the other.
These can be used as pinion wheels for something like a train that goes along a rack track, or sometimes as a pinion wheel that climbs up and down a pole that has a rack on it.


(from: wikipedia - rack and pinion)


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Air Gap

We just learned about the Electromagnet.

Another part of the electric motor is the Air Gap.

We learned that the rotor is the part that spins around in the middle, and the stator is the part that is wrapped around it.

The very small space between the rotor and the stator is the air gap.

The smaller the air gap, the better the electric motor will work, but it also needs to be enough space that the rotor won't hit the stator as it is spinning around.


(from: wikipedia - electric motor)


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