What is an Encoder
Summary
TLDRIn 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
🔍 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.
🔧 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.
📢 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.
Mindmap
Keywords
💡Encoder
💡Position Feedback
💡Incremental Encoder
💡Absolute Encoder
💡Hollow Shaft Encoder
💡Solid Output Shaft
💡Pulses Per Revolution (PPR)
💡Optical System
💡Power Cycle
💡Homing
💡Communications Technology
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
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