optical shaft encoder

Rengas · May 26, 2013

Hi everyone,

Can anyone please explain why the output of an optical shaft encoder is inherently digital?

I appreciate you all reading this.
Thank you

bernie_carlton · May 26, 2013

A rotary pot would have an analog output. But the name "encoder' MEANS that the rotary position is ENCODED as a number - digital.

What were you expecting?

DickDV · May 26, 2013

Usually, an optical encoder is built so a light source shines thru slots in a rotating wheel producing a pulsating light signal on the optical receiver. The number of slots in the wheel give the ppr or pulses per revolution for the encoder.

I guess the pulses make it necessarily digital.

CalG · May 26, 2013

As described, an optical encoder makes use of a radiation source (a "light"), and a radiation detector (the sensor) between them is a moving patterned mask that can block or transmit the "light" to the detector. A single detector with two states, On or Off. Light yes, or light no. depending on position.

It would be possible to have variable intensity sensitivity, but that is not typical

Lancie1 · May 26, 2013

I am going to jump all over a bunch of you all, as you have jumped me for doing student homework!

Just kidding, I am not the knowledge police!

I believe that knowledge should be shared, student or otherwise. We all have to learn somehow somewhere. Why not now?

dcooper33 · May 26, 2013

Lancie1 said:
I am going to jump all over a bunch of you all, as you have jumped me for doing student homework!

Just kidding, I am not the knowledge police! I believe that knowledge should be shared, student or otherwise. We all have to learn somehow somewhere. Why not now?

I bet poor Orwell is rolling over in his grave

+1. I can't say that I've ever seen anyone who was ever worse off for freely sharing their hard-gained knowledge. I have known a few miserable old cusses who willfully hoarded their expertise. I doubt it ever got them anywhere.

And to further the OP's question, any encoder, whether incremental or absolute, is inherently digital, but how would you classify a resolver? Technically, they output a pair of analog signals, but no programmer ever works with these variable signals. We only see the digitized "counts" from the ADC. (Of course the same could be said of any analog signal) So is a resolver inherently digital or analog?

Peter Nachtwey · May 27, 2013

In the end, everything is still analog. Just ask any high speed circuit board designer.

I believe knowledge should be shared to but at a such a basic level I expect a little research to be done first. If a person isn't going to put forth at least a little effort he isn't worth my time and should find another job that doesn't required looking up a pdf file and reading it. Yeah, I know, what a grump.

OkiePC · May 27, 2013

Peter Nachtwey said:
In the end, everything is still analog. Just ask any high speed circuit board designer.

I believe knowledge should be shared to but at a such a basic level I expect a little research to be done first. If a person isn't going to put forth at least a little effort he isn't worth my time and should find another job that doesn't required looking up a pdf file and reading it. Yeah, I know, what a grump.

My electronics professor in college was a radio engineer and military radar expert and he laughed and he lectured about the latest gains in internet speeds and wifi, and explained how digital goes nowhere without high speed analog and its the analog side that is improving. or was at that time and in his time.

Rengas · May 27, 2013

Peter Nachtwey said:
In the end, everything is still analog. Just ask any high speed circuit board designer.

I believe knowledge should be shared to but at a such a basic level I expect a little research to be done first. If a person isn't going to put forth at least a little effort he isn't worth my time and should find another job that doesn't required looking up a pdf file and reading it. Yeah, I know, what a grump.

The PDF file was the resource we were given. I am a complete novice in PLCs. I had no idea what it was until i started my electrical course. I diddnt even know it was going to be on the course. And it doesn't also help when i know nothing about electrics and having to quickly learn them. Those doing well in my class are already qualified electricians.

Thanks for your reply anyway.

Rengas · May 27, 2013

Thanks Lancie, Barnie, OkiePC, Peter Netchway, bmacattck33, you are always here to help.
Nice people.

Rengas · May 27, 2013

OH and thanks to DickDV and CalG as well.

Rengas · May 27, 2013

Peter Nachtwey said:
In the end, everything is still analog. Just ask any high speed circuit board designer.

I believe knowledge should be shared to but at a such a basic level I expect a little research to be done first. If a person isn't going to put forth at least a little effort he isn't worth my time and should find another job that doesn't required looking up a pdf file and reading it. Yeah, I know, what a grump.

I already did the research as to what an optical shaft encoder is. its just the digital bit i wasn't getting which is why i posted the question here. And the name of this device gives the meaning away. i already had an idea what it should be. optical (we all know what ''optic'' means)......... shaft (there should be a rotating shaft)......... then encoder (code).

Lancie1 · May 27, 2013

I have known a few miserable old cusses who willfully hoarded their expertise. I doubt it ever got them anywhere.

A bunch of those here are peple who get paid to share their knowledge. If I were in that position, I too might frown on it being handed out free. The problem is that there is plenty of nearly-free knowledge out there now, so it is not as easy as it once was to get paid for delivering knowledge.

dcooper33 · May 27, 2013

Lancie1 said:
A bunch of those here are peple who get paid to share their knowledge. If I were in that position, I too might frown on it being handed out free. The problem is that there is plenty of nearly-free knowledge out there now, so it is not as easy as it once was to get paid for delivering knowledge.

Point taken.
I think you mistook me, though. By definition, any who freely contribute to this forum, no matter their manner of delivery, can't be classified as the kind of folks I was talking about.

I was talking about the kind of guy who won't share info or knowledge with his colleagues or subordinates, for fear it will make him less valuable to his employer. Or maybe sometimes it's out of pure spite. Who can say?

Not wanting to solve someone's problem for them when all it would take is a little thought and/or research on the querent's part is understandable. But withholding knowledge from someone who really wants to learn is senseless, IMO

shooter · May 28, 2013

well rengas there are also optical encoders fully analog working with a displacement sensor giving two signals X+ and X-, with some opamps it gives an analog signal of position, they can be very precise like 0.1 um.

optical shaft encoder

Rengas

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bernie_carlton

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DickDV

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CalG

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Lancie1

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dcooper33

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Peter Nachtwey

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OkiePC

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Rengas

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Rengas

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Lancie1

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dcooper33

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shooter

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