Talk:Rotary encoder

simple two-channel

This article needs more coverage of the simplest case -- show the innards of a standard computer mouse, and show the two-channel encoding and explain how it works, how the counters are interfaced. This article needs to be a tech support base for the mouse articles.-69.87.203.252 13:45, 20 March 2007 (UTC)

Yes. Anybody have a good, clear photo of the inside of an optical encoder? I put up a photo of a Hall-effect quadrature encoder (yes, that really is a quadrature encoder), but that's a sealed unit and you can't see how it works. --John Nagle (talk) 04:53, 11 December 2007 (UTC)

Encoder Disk Image

Is this image right? I think that there is something wrong with the numerical sequence: 0,1,3,2,6,7,5,4. Where did this image come from?--Drvanthorp 16:21, 5 September 2007 (UTC)

Items that need coverage

A few items that need coverage:

• The "once per turn" signal on an encoder is called an "index pulse". It's not enough for absolute positioning. It's usually used in conjunction with some other means of low-accuracy position sensing, like a limit switch. In such systems, startup calibration involves moving to a limit switch, then back to the next index pulse point.
• Brush-type encoders are rare today.
• Some "incremental encoders" are unidirectional, with only one Hall sensor. Automotive speedometer and tachometer inputs are single-sensor encoders, usually called tachometer sensors.
• Sometimes a resistive position sensor and an encoder are combined into a single unit, to obtain a position at startup. Automotive steering position sensors work this way. —Preceding unsigned comment added by Nagle (talk • contribs) 16:27, 10 December 2007 (UTC)

Fundamental Flaws

Much of this article makes the fundamental mistake of essentially stating that the function of absolute encoders is true of all rotary encoders. This is further compounded by the fact that absolute encoders are the less common of the two types. I plant to make a tweak or two regarding this but do not plan to do the major work needed to really fix this issue and the article. Sincerely, North8000 (talk) 14:11, 6 March 2011 (UTC)

Why restrict to rotary

Not all encoders of this type are rotary. Some are linear, consisting of straight strips. — Preceding unsigned comment added by 192.139.122.42 (talk) 22:33, 27 May 2011 (UTC)

But all rotary encoders are rotary! :-) I guess it's the title that did it. But we should mention that the same functions are available in a linear format. North8000 (talk) 23:10, 27 May 2011 (UTC)

Scrambled subsection

The "Battery backed incremental encoders" makes no sense. I tried going to the referenced document to see what the editor intended to say but it a huge users manual which covers a huge range of products which makes no coherent statements regarding the material which cited it. North8000 (talk) 12:26, 9 February 2012 (UTC)

I deleted it.North8000 (talk) 12:46, 15 February 2012 (UTC)

bogus info

the text in the section Incremental rotary encoder seems bogus to me. It basically suggests that applications have to (or do) use lookup tables to decode the signal from the encoder - whereas a look at the diagram reveals that that's not necessary. If the shaft is rotated clockwise (imagine a line gliding over the diagram from left to right) every rising edge of A coincides with B being low. A CCW rotation would make B being high on every rising edge of A. So, all the application has to do is to track A's rising edges and B will invariably indicate the direction. I'm not an electrical engineer (only an enthusiast), but I imagine this not only is simpler in terms of circuitry but also the way it's actually done in the real world. Уга-уга12 (talk) 19:27, 1 May 2012 (UTC)

The way that you describe it correctly describes a way to do it and implements what is called "X1" logic. It requires the occurence and direction of transitions. It is common practice to do this for all four edges that occur for a quadrature signal in one signal to obtain "X4" logic, and get 4x the resolution. The tables in the section (and related description) seem to imply/describe another method which derives information from knowing the current and previous state of the outputs. I don't know whether or not that other method is actually used. North8000 (talk) 20:26, 1 May 2012 (UTC)

The discussion above from "Уга-уга12" appears to disagree with the wiki article regarding the interpretation of clockwise versus counterclockwise using A and B. — Preceding unsigned comment added by 12.236.43.222 (talk) 16:59, 16 May 2012 (UTC)

Following is just a sidebar comment......there is no widely accepted standard for the phasing in relation to clockwise and CCW. And in the case of double shaft encoders, there really is not even a definition of clockwise vs. counterclockwise. Sincerely, North8000 (talk) 11:42, 24 May 2012 (UTC)

Bar-code type absolute encoder

A new type of absolute encoder has been developed.[1] This uses a bar code that represents position, and is read by a camera IC, not a single sensor. It takes some compute power, but it's a high-resolution absolute encoder. Available for both linear and rotary encoders. No news articles yet, so I'm not putting it in the article. A design note from Taos suggested this idea in 2004 [2] but apparently nobody picked up on the idea until recently. I'm surprised it took so long; the processing is simpler than that for an optical mouse. --John Nagle (talk) 00:12, 3 September 2013 (UTC)

I think that an independent article would be important. The material that you linked (by the supplier) seems written to impress rather than really explain. Sincerely, North8000 (talk) 11:26, 3 September 2013 (UTC)

These have been around for 30 years (at least). The Renishaw version is just an improved development, with improved performance to the read head and the idea of a single staring camera rather than the linear array of single sensors (although I did something similar myself with a line-scan camera, 20 years ago). The idea of single-track non-repeating-code is important and deserves mention here, but it's quite old. At present the article seems to skip them and goes straight to the single track Gray code (i.e. only one bit changes per increment), which is much later. Andy Dingley (talk) 11:33, 3 September 2013 (UTC)

First Citation (rotary encoder on canon lenses)

The page for the first citation has been deleted. The old content can be found from the wayback machine here: https://web.archive.org/web/20131005090254/http://www.canon.com/bctv/faq/rotary.html — Preceding unsigned comment added by 122.107.192.94 (talk) 12:25, 12 March 2015 (UTC)

Done, but it is a dubious reference. Glrx (talk) 17:04, 1 April 2015 (UTC)

Analog encoders

There's an unreferenced mention of "sine encoders", which are analog quadrature devices. Here's a reference.[3]. See also Resolver (electrical). John Nagle (talk) 17:21, 15 February 2016 (UTC)

Deletion of chart and mini-discussion in edit summaries

Reference is made to to the last couple edits. An editor deleted the chart saying that it was incorrect. I reverted, saying that the chart was correct and useful to help explain the derivation of direction of the quadrature signal. The same editor undid my restoration, in essence saying that direction could be derived from the previous and current state. This is not relevant to either of the content issues being discussed. Including no discussion on whether the deleted chart is correct or not. Indeed, it is correct (which they did not challenge when they reverted my restoration) and it shows how very similar-appearing waveforms / sequences are different when the rotational direction changes. This is correct and useful content to help explain the topic. Thoughts? Sincerely, North8000 (talk) 23:21, 8 August 2017 (UTC)

IP's edits were appropriate and should remain. Using two diagrams with different "phase" assignments is confusing. Glrx (talk) 02:41, 14 August 2017 (UTC)

Headings

Lambrton, you did a lot of good work. But some of it has scrambled it a bit from an organization and naming standpoint. "Absolute" is duplicated and incremental is not necessarily digital. I didn't revert because I think you can resolve with further evolution. North8000 (talk) 12:14, 22 June 2018 (UTC)

@North8000: Thanks for the positive feedback -- and for collaborating on the clean-up. I realize it's disorganized and plan to work on that. I also see what you mean about duplicate titles (and other duplication) and will take a crack at fixing those too. Lambtron (talk) 12:58, 22 June 2018 (UTC)

Cool! North8000 (talk) 17:49, 22 June 2018 (UTC)

First pass completed. Let me know what you think, or feel free to modify it as you see fit. Lambtron (talk) 17:58, 22 June 2018 (UTC)

Cool. Perhaps a bit more on the fundamental nature of the info they or their system put out? Absolutes put out position. For incrementals they need the next stage to derive motion variables but this list is longer (position, velocity, RPM, distance moved etc.? North8000 (talk) 21:14, 25 June 2018 (UTC)

Split proposal

Proposal

• Move generic parts of Rotary encoder#Incremental encoder → Incremental encoder
• Add a summary of the removed content with a link to incremental encoder

Rationale

"Incremental encoder" is a topic worthy of its own article. Currently, incremental encoder redirects to this article's "Incremental encoder" section. That section, for the most part, provides in-depth coverage of generic (both rotary and linear) incremental encoders, thus making it ideal content for incremental encoder. At more than 40% of this article, the length of the relevant content is out of proportion to the rest of the article, so moving it will rebalance and restore the focus of rotary encoder. The resulting incremental encoder article will provide common background information for, and thereby avoid duplication in articles related to incremental encoders.

Discussion

• Support - For the reasons given above. Also, I plan to add more content about incremental encoders which is not exclusive to rotary devices and will further unbalance this article. Lambtron (talk) 15:23, 17 July 2018 (UTC)

Well, there are the 4 categories:

• Rotary absolute
• Linear absolute
• Rotary incremental
• Rotary absolute

And they can be mid-level grouped by 2 schemes:

• Linear vs. (has an article)
• Rotary (has an article)

and

• Incremental vs.
• Absolute

And a top level article that includes all 4 would be a good idea but has no usable name that I can think of. (Simply "Encoder" includes too many unrelated things.)

So right now Wikipedia is covering all of the above in 2 articles using / implementing the rotary vs. linear scheme. IMHO what you are proposing would be (in Wikipedia terms) starting a new classification scheme. This sets it up for inevitable overlap. Plus material that you are moving isn't "incremental encoders" it's "rotary incremental encoders." If you were to make the new article "Rotary incremental encoders" it would match the material that you are moving, and just be a more specialized article rather than introducing a new overlapping organizational scheme. Thoughts? Sincerely, North8000 (talk) 17:56, 17 July 2018 (UTC)

"Incremental encoder" is not a "new classification"; it's an industry-standard term for linear or rotary devices with quadrature digital outputs (e.g., see this and this). I agree that the proposal will create a comprehensive, "specialized article" about this distinct topic -- and in the process restore balance to rotary encoder and avoid content duplication in other articles, as explained in my Rationale. As for the content being moved, please read the proposal more carefully: subsections which are specifically about rotary incremental encoders will not be moved (in particular, the sections "Incremental rotary encoder" and "Other pulse-output rotary encoders"), and the proposal has nothing to do with absolute encoders. In view of these facts, would you support the proposal? Lambtron (talk) 19:16, 17 July 2018 (UTC)

Support despite my minor quibble, because you are doing an immense amount of good work here and I want you to have a pretty free hand to keep moving forward. My "minor quibble" is not that it's a "new classification", it's that you are entering Wikipedia into a second article organization classification approach on encoders. The existing classification approach (for mid level articles) is rotary vs. linear. But the issue is minor; such things are common on Wikipedia, they just create some duplication. North8000 (talk) 09:57, 18 July 2018 (UTC)

Thanks for the feedback and support -- both are greatly appreciated. I don't intend to change the existing rotary vs. linear classification system, which will continue to be the primary distinction between position encoder types. My goal is to factor generic incremental out of rotary and linear (and elsewhere) and thereby avoid duplication, allow it to expand without further overweighting rotary (or linear, where it could just as easily and justifiably reside), and treat it as the distinct topic it is. IMO this is not a controversial split and, since I have your support and no other page watchers have shown interest, I have implemented the split as proposed.

Cool! North8000 (talk) 19:30, 18 July 2018 (UTC)

Info on "Royal Radar Establishment code"?

Researching Gray code variants for our Wikipedia article I stumbled upon a code called "Royal Radar Establishment code" in a 1972 book, apparently used in some kind of displacement measurement devices (possibly linear or rotary encoders):

Wightman, Eric Jeffrey (1972). "Chapter 6. Displacement measurement". Instrumentation in Process Control. Butterworth & Co. pp. 122–123. ISBN 0-408-70293-1.

The book states:

"Other forms of code are also well known. Among these are the Royal Radar Establishment code; The Excess Three decimal code; Gillham code which is recommended by ICAO for automatic height transmission for air traffic control purposes; the Petherick code, and the Leslie and Russell code of the National Engineering Laboratory. Each has its particular merits and they are offered as options by various encoder manufacturers."

If you have any information about this code, please ping me/reply. Thanks. --Matthiaspaul (talk) 21:10, 21 May 2020 (UTC)