What is an Encoder

Summary

In this educational video, Henry explains the function and differences between incremental and absolute encoders. He demonstrates how encoders, used for position feedback in rotating mechanisms, work by converting optical pulses into electronic signals. Incremental encoders send a series of pulses to a controller, which counts them to determine position, but require homing after power cycles. Absolute encoders, on the other hand, maintain position information even through power cycles due to their unique addressing system for each position. The video also touches on the applications of each type of encoder, with incremental encoders suitable for systems like conveyor belts where absolute position isn't critical, and absolute encoders ideal for precise, high-dependency machinery.

Takeaways

• 😀 Encoders are used for position feedback in rotary mechanisms.
• 🔍 They can be connected to a rotating shaft to determine the position of an object.
• 🔧 Encoders have a mechanical disc inside that rotates with the shaft, which is read by an optical system to generate electrical signals.
• 💡 Incremental encoders send a series of pulses that a controller counts to determine position, but require homing after power cycles.
• 🔄 Incremental encoders can detect direction (forward or reverse) and adjust the pulse count accordingly.
• 📊 Absolute encoders have a unique address for each position, allowing them to retain position information through power cycles without homing.
• 🔗 Encoders can communicate with controllers via various methods, including specialized proprietary communications or standard Ethernet IP.
• 🏭 The choice between incremental and absolute encoders depends on application requirements, such as the need for precise positioning and whether homing is acceptable.
• 🔩 Encoders are used in various environments, from precise machinery with multiple servos to simpler applications like conveyor belts.
• 📈 The video provides practical examples, such as using an encoder on a conveyor belt to track position for robotic picking.

Q & A

What is an encoder?

An encoder is a device used for position feedback, typically connected to a rotating shaft to provide information about the position of a rotary mechanism.

How does an encoder work?

Encoders work by having a mechanical disc inside that is attached to the rotary mechanism. As the disc spins, it has etchings that interact with a reader on the circuitry, converting optical pulses into electronic signals that can be sent to a controller.

What is the difference between a hollow shaft encoder and a solid output shaft encoder?

A hollow shaft encoder has a center hole where a shaft can be inserted and coupled, while a solid output shaft encoder has a continuous solid shaft. Both types have the same operating principle but differ in how they connect to the rotary mechanism.

What is an incremental encoder?

An incremental encoder is a type of encoder that sends a series of pulses to a controller, which counts these pulses to determine the position. It does not retain position information through a power cycle and requires homing to reset the count.

What does PPR stand for in encoder terminology?

PPR stands for Pulses Per Revolution, which indicates the number of pulses an encoder sends per complete rotation of the shaft.

How does an absolute encoder differ from an incremental encoder?

An absolute encoder retains its position information even through a power cycle, as it has a unique address for each position on its disc. It does not require homing like an incremental encoder.

What is homing in the context of encoders?

Homing is the process of resetting the position count to a known starting point when the system is powered on, necessary for incremental encoders because they lose position information during a power cycle.

Why would someone choose an incremental encoder over an absolute encoder?

An incremental encoder might be chosen for applications where the cost is a factor and the system can afford to spend time homing after a power cycle, such as in a conveyor belt system where absolute position information is not critical.

What is the advantage of using an absolute encoder in a system with multiple servo motors?

In a system with multiple servo motors that need to maintain specific alignments and positions, an absolute encoder is advantageous because it can retain position information through power cycles, avoiding the time-consuming process of homing all motors.

What is the purpose of the etchings on the encoder disc?

The etchings on the encoder disc are used to modulate light as the disc spins, creating a pattern of light and dark that the reader on the encoder's circuitry can interpret as electrical signals representing position.

How does the communication technology differ between an incremental encoder and an absolute encoder?

Incremental encoders typically have more wires due to the need to send multiple pulse signals for position and direction, while absolute encoders may have fewer wires because they send a unique position signal that represents the absolute position on the disc.

Outlines

00:00

🔍 Introduction to Encoders

The first paragraph introduces the concept of encoders, which are advanced sensors used for position feedback. It explains that encoders are connected to rotating mechanisms and help determine the position of an object. The discussion includes the difference between hollow shaft and solid output shaft encoders, and the general principle of how they work. An encoder contains a mechanical disc with etchings that, when rotated, creates an electrical signal through an optical system. This signal is then sent to a controller. The paragraph also distinguishes between incremental and absolute encoders, with incremental encoders sending a series of pulses that a controller counts to determine position, and the ability to sense direction of rotation.

05:01

🔧 Understanding Incremental and Absolute Encoders

The second paragraph delves deeper into the differences between incremental and absolute encoders. Incremental encoders lose their count upon power loss, requiring a homing process to reset the position. In contrast, absolute encoders maintain their position information even after power cycles due to a unique addressing system for each position. The paragraph also touches on the different communication technologies used by these encoders, such as Rockwell Automation's DSL feedback and Ethernet/IP, which allow for communication with controllers over standard networks. The discussion concludes with examples of where each type of encoder might be used, emphasizing the importance of application requirements in choosing the right encoder.

10:03

📢 Promoting ESN TV's Educational Content

The third paragraph serves as a call to action for viewers to engage with the content by subscribing to the ESN TV YouTube channel, liking the video, and enabling bell notifications for updates. It suggests that viewers who are interested in learning more about encoders and similar topics should follow these steps to stay informed about new educational content.

Keywords

💡Encoder

An encoder is a device that converts information from one format or code to another, often used for position feedback in mechanical systems. In the video, encoders are used to determine the position of a rotating object by connecting the encoder's shaft to it. The script mentions hollow shaft and solid output shaft encoders, indicating different types of encoders designed for various applications.

💡Position Feedback

Position feedback refers to the process of determining the position of a mechanical component, such as a shaft, within a system. The video script explains that encoders provide this feedback by connecting to a rotating mechanism, allowing the system to know its exact location at any given time.

💡Incremental Encoder

An incremental encoder is a type of encoder that provides relative position information by counting pulses. The script describes how it works by sending a series of pulses to a controller, which counts these pulses to determine the position. An example from the script is the encoder with '1024 PPR' (pulses per revolution), which allows the system to know how many revolutions have occurred.

💡Absolute Encoder

An absolute encoder, in contrast to an incremental encoder, provides a unique position for each degree of rotation, even after a power cycle. The script explains that absolute encoders have specialized mechanical systems that allow them to retain position information, making them useful for applications where maintaining position after a power loss is critical.

💡Hollow Shaft Encoder

A hollow shaft encoder is a specific type of encoder with a hollow center that allows a shaft to pass through it. The script mentions that this type of encoder can be coupled to a rotating shaft, making it suitable for applications where the encoder needs to be attached to an existing rotating component.

💡Solid Output Shaft

A solid output shaft encoder has a solid shaft that cannot accommodate another shaft passing through it. As described in the script, this type of encoder is directly connected to the rotating mechanism, and is used when the encoder is an integral part of the rotating system rather than an attachment.

💡Pulses Per Revolution (PPR)

PPR is a term used to describe the number of pulses an encoder generates for each complete revolution of the shaft. The script uses the example of '1024 PPR' to illustrate how the controller can determine the position of the encoder by counting these pulses.

💡Optical System

The script mentions an optical system within the encoder, which uses a light source and a reader to detect the etchings on a rotating disc. This system converts the physical pattern on the disc into electrical signals, which represent the position information.

💡Power Cycle

A power cycle refers to the process of starting up or shutting down a system, which can affect the state of components like encoders. The script explains that incremental encoders lose their position count during a power cycle, requiring a homing procedure, whereas absolute encoders retain their position information.

💡Homing

Homing is the process of determining and setting a known position at the start of a system's operation. The script discusses how incremental encoders require homing after a power cycle to establish a known starting point for position counting.

💡Communications Technology

Communications technology in encoders refers to the methods used to transmit position data from the encoder to the controlling system. The script mentions DSL feedback and Ethernet IP as examples of such technology, highlighting how encoders can communicate position information over different types of networks.

Highlights

Introduction to encoders as advanced sensors for position feedback.

Explanation of how encoders connect to rotating objects to determine their position.

Description of the internal components of an encoder, including a mechanical disc.

The role of the etched disc in an optical encoder system.

Conversion of optical pulses into electronic signals by the encoder.

Incremental encoders explained, including their pulse counting mechanism.

The significance of 1024 PPR (pulses per revolution) in incremental encoders.

Capability of high-quality encoders to detect direction (forward or reverse).

Difference between incremental and absolute encoders, especially after power cycles.

Mechanisms of absolute encoders to maintain position information post power cycle.

Practical example of using incremental encoders in conveyor belt systems.

Advantages of absolute encoders in systems requiring precise alignment and interdependency.

The necessity of homing in incremental encoder systems and its impact on efficiency.

Comparison of wiring complexity between incremental and absolute encoders.

Introduction to DSL feedback and Ethernet IP encoders for communication with controllers.

Practical application considerations for choosing between incremental and absolute encoders.

Encouragement to like, subscribe, and enable notifications for more educational content.

Transcripts

[Music]

[Music]

hi Henry what's that oh it's an encoder

[Music]

oh

[Music]

all right Henry I assume these are

encoders they are encoders they're used

for position feedback okay so what you

do usually is you take the shaft of the

encoder and you connect it to something

that is in this case

rotating and it allows you to tell where

in the rot

that object

is okay so is it like a sensor yeah it's

a it's a really Advanced sensor yeah

they're used to tell some sort of

control device where a rotary mechanism

is well I don't know anything about them

so could you please explain uh the

differences in these encoders sure I

think let me start by explaining the

general principles of how encoders work

okay so I have one here that I think we

can take

[Music]

apart there we go so we can get inside

this

guy and it's got these screws

here so now that I've got those screws

off you can sort of see what's going on

underneath the circuitry well I can see

it but I have no idea what's going on

fair enough so there's this little disc

do you see that disc I do I do so that

disc is connected to the shaft of the

encoder and so in this particular case

this is a hollow shaft encoder so

there's actually going to be a shaft

that goes into this one and then there's

a a

coupling that will clamp onto the shaft

and you know capture it right there's

other encoders like this guy he's got a

solid output shaft so this is a solid

output and the one I'm looking at now is

a hollow shaft

encoder so but they all they all

generally have the same operating

principle okay they all have this little

mechanical disc inside that is attached

to the rotary mechanism and that disc

goes round and round and round and it

has an etching in the disc I don't know

if you can see the those lines in there

or not but is it like a record it's

similar to that yeah this so this

particular one is pretty close to like a

DVD or a record or a CD right so I've

got a reader on the circuitry right and

a light source underneath it and so as

those etchings on the disc go around and

round it communicates an electrical

signal you know this is an optical

system right so it's basically

converting

Optical uh pulses into a an electronic

signal and then it can send those

signals to these wires and send it to a

controller of some kind is this sensor

underneath here is it looking at

different levels of light or is it like

a one and zero is it yeah it's so it'll

basically be like a one or a zero right

so this one this encoder here is what

you would call an incremental encoder so

what that means is that there is a

series of pulses that are going to be

sent through these wires to a controller

of some kind the controller will count

up the number of pulses as they're

coming in and it can determine what the

position is by counting the number of

pulses so let me stick this back

together CU I've got my sticker cut in

half here there we go so you can see

there it says

1024 PPR

right so that would be

1,24 pulses per Revolution when I get to

a24 I know I've gone one revolution if I

get to double that I know I've got two

revolutions and if I get half of that

I've gone half a revolution right so you

can do the math to figure out where you

are and then in this particular case

this is actually a pretty uh high

quality encoder this one is actually

able to tell the the processor if I've

gone forward or reverse so there's two

sets of pulses now that's why there's so

many different wires it's not just one

set of pulses there's one for telling if

I've gone forward one for telling if I'm

going in the reverse Direction so then

you can start adding pulses and

subtracting if I go forward I add pulses

if I go backward I remove the pulses so

this is a incremental encoder there was

an absolute encoder also that's right so

incremental encoder and then we have an

absolute encoder this one's also an

absolute encoder off of the back of a

Servo motor all right what's the

difference here the main difference is

uh what happens during a power cycle

with an incremental style encoder you're

adding pulses and subtracting pulses

when you turn off the system you lose

that count and you have no way of

knowing where you are on the encoder

disc anymore so you have to do something

called homing so that when you start up

the system at the beginning you're

starting at a specific point and you're

telling the controller where you are and

then you can start counting from that

point with an absolute style

encoder there is uh even more

specialized mechanical systems inside of

these that allow you to know where you

are even through a power cycle so

there's an etched disc another uh

specialized etched disc inside of this

style of encoder that it basically has a

unique address for each position all the

way around as you rotate that shaft of

the encoder the encoder can always tell

you exactly where it is because you know

if you think about it every maybe maybe

you call it a degree Mark every degree

knows has a

specific address for lack of a better

term so this one is different from this

one is different from this one right

right so you're always able to tell the

controller where it is and you don't

necessarily need to home every time you

have a power cycle absolute encoders

have some sort of communications

technology built into them um you can

see this is an absolute encoder there's

only like four wires coming out of it so

that's a lot simpler than this

incremental encoder that has several

wires coming out of it um that's because

there's a lot more computational uh

processing happening inside of this

encoder and then those signals that

information is being sent to the

controller via some sort of

communications this is a what Rockwell

Automation calls DSL feedback so digital

Servo link it's a specialized

proprietary Communications that Rockwell

uses um this encoder here is an ethernet

IP encoder so you can communicate with a

controller over ethernet just standard

unmodified uh network

communications why would you use one or

the other in an in what environments

yeah so it really comes down to

application requirements right so let's

say I've got a system with 100 Servo

Motors on it and they're all in very

specific spots in the machine they're

all aligned and maybe they're inter

dependent right so if I move I can't

move one without the other right if I

have a power cycle in that situation and

I have an incremental encoder system I'm

going to have to rehome everything and

that process can take a long time so

that would be a a system in which you

would want to spend a little bit more

money so that you don't have to waste

money after the fact when you're

actually running your equipment okay do

do you have like an example of uh like

where I could use an incremental

something like a conveyor belt so if I

need to know where a conveyor is um you

know let's say I'm moving this encoder

for example and I'm moving this encoder

and I need to know where it is on the

conveyor belt so that let's say a robot

can come pick it up right so what I

might do is attach a encoder to the

conveyor belt so that I can see where it

is on the on the Belt if there's a power

cycle it's not really that big of a deal

to have to rehome that system there's

also sort of a repetitiveness aspect of

a conveyor right it's going to just go

around and round and round right so it's

okay that I don't have absolute position

information about where something is on

that belt well I think I understand a

lot more about encoders than I did when

I walked onto this stage so thank you

yeah absolutely happy to do at any time

oh cool all right oh hey Phil oh yeah if

you'd like to learn more about this kind

of thing you can always like And

subscribe to our ESN tv YouTube channel

and you should probably uh like this

video and hit the Bell notification too

so that you get notifications that's a

great idea

[Music]

awesome