Low Cost Encoders
 

Recently a number of encoders have popped up on ebay like this and this with excellent prices (<15$)! Considering the cost of some name brand rotary encoders they look like a excellent option for applications that do not require perfectly calibrated sensors. They are also available for purchase in small quantities unlike a number of other encoders. Does anyone have any experience with them?

Re: Low Cost Encoders
 

Not yet but I soon will :confused:.
I will let you know when they arrive.

Re: Low Cost Encoders
 

Great, I would grab a few for myself to review but It will be a while until I get purchasing access. Most of the items I order from china take about 2-3 weeks to arrive.

Re: Low Cost Encoders
 

Got the encoders today.

5 wires each
A & B
Vcc / System ground
Shield ground

Color code in Mandarin Chinese.
Actually not a problem.
http://mandarin.about.com/od/vocabulary/a/colors.htm

Black = system ground
Red = Vcc
Shield ground is black higher gauge or bare
White, Yellow, Green are A & B

Will power them up tomorrow.
These are likely too big for AndyMark gear boxes without shaft couplers and spacers.

Re: Low Cost Encoders
 

I would rather pay little more and buy from someone who has designed and made the encoders (or anything or from any country for that matter) as long as they own the intellectual properties for the product. It's unfortunate that many companies steal designs or copy products from others and make quick buck.:mad:

Re: Low Cost Encoders
 

No offense but optical encoders have been around for decades.

As much as I too would like to take the 'high road' here:

First let us start with a basic question: who invented the first shaft encoder?
You are tossing around the suggestion that they stole it.
So let us demonstrate from whom.
Consider this a lesson for the students.
Hint: Look up Murray Hill, NJ....Dr. John Northrup Shive....Bell Telephone Laboratories.

I take some issue with the use of non-American parts to operate U.S. FIRST as well.

Then again ask National Instrument to catalog where their parts and assembly come from.
The $2,000+ 8 slot cRIO myself and another mentor bought was shipped to us from Turkey.
That doesn't sound like 'Made in America' to me.

So why is it okay to use labor unknown from one country but not another?
Can you prove that abuses of labor are any less in one place than the other?
Have you personally checked?

Keep in mind when I bid on the 2015 control system I was going to do *all* the assembly in the United States.
I flatly stated in writing that the additional cost was irrelevant to the potential quality control issues.
Never mind the potential language barrier (my Chinese is laughable).
I did not suggest these other countries were thieves without evidence.
Here's your chance show your evidence.

I note that in the topic about the RoboRio you never asked where that product came from but did admire the cost savings.

Further *who am I* to decide that teams with deep pockets are more entitled to working encoders than teams just managing to show up? Why should those with less in their purse not buy parts probably made by those with less in their purse?

Now I have encoders to test you seem relatively new here you might want to take note:
Of all the people you could try to insert your politics with >I am the last person on Earth< to do it with.
If I think your case is questionable I will poke holes in it.
It is not personal nor is it about whom you are with politically or otherwise.
It is merely my scientific method which is quite incompatible with politics.
Do not assume that as a member of Team 11 they control me either or that I speak for them.
I am me and my choices are my own.

Sorry if that's a little rough but when you end on an angry emoticon you should recognize the types of response you might get back.

Re: Low Cost Encoders
 

Have not forgotten about this.
Dealing with a Linux bug that has some urgency.
Will have an answer before Sunday.

The A&B outputs appear to be open-collector.
So I will set these up and turn them with a motor then sample the output quality and provide it.

I will also work up a circuit to divide the output down to encoder resolutions more common to FIRST.

Re: Low Cost Encoders
 

These look a lot like the encoders made by 1114's sponsor Industrial Encoder Corporation.
Interesting.

Re: Low Cost Encoders
 

I will be glad to take one apart and photograph the guts.
At that point it should be clear if these are actually a knock off.

Re: Low Cost Encoders
 

If you google "rotary encoder" you'll find 100's of companies that produce encoders that look nearly identical to these ones. Who copied who? No one really knows.You pay a premium to buy from American companies like Industrial Encoders because they don't just sell encoders they sell a product that comes with technical support and the guarantee that you'll get a perfectly calibrated encoder that will last years. This is great for a company like HAAS but not necessary for most teams. The end product is almost entirely different.

Re: Low Cost Encoders
 

I wouldn't be so quick to say a lower quality encoder is sufficient for our use.

If the lower quality means an increased failure rate, we'd pass on that. The encoders we get from us digital aren't crazy expensive, and we'll always pay to not lose matches due to preventable failure.

Re: Low Cost Encoders
 

We have no way of knowing the quality of anything until tested.
Even then even it's maybe 3 encoders out of who knows how many lots.

Frankly there are way more ways I can think of ruining encoders in general in FIRST than there are ways I can imagine these are complete junk from my first examination.

There is literally a bag of ruined U.S. Digital encoder parts floating around our workshop.
Each has a story.
However one way or another we have limited our exposure to the U.S. Digital encoders.

Not saying it's U.S. Digital's fault.
Just saying we'll be using sealed encoders where possible in the future.
Though they may or may not be the encoders in this topic.

Re: Low Cost Encoders
 

Interesting, we've run at least 2 (and as many as 8) Us Digitial s4's on every robot since 09 without a single failure. Practice bots and multiple offseason bots included.

Re: Low Cost Encoders
 

Glad they are working out for you.
We've not been so lucky.

Sometimes it's how they were installed.
Sometimes it's how they got damaged during play.
Often times it's adjusting the disc.
I personally destroyed a pair because of a wiring error with the tiny connectors (my fault and I admit it).
We've had a few that no matter the encoder wheel read unreliably (confirmed with an oscilloscope).
They are often in places that it is just plain hard to work on them.

Plenty of that is us and some of that is just the issue of something delicate in the midst of something not very delicate.

Finally last year we got fed up and ordered some sealed encoders from Digikey and had better success.
They cost more but like you said sometimes it's not worth the savings.
They had 0.1 inch spaced header pins so that reduced the tooling, the connectors and the tails.
Never mind the aggravation of remembering to haul around that extra stuff.

Would I use a U.S. Digital encoder on my own professional stuff?
Sure but my professional stuff is not designed, installed or treated like this.

Re: Low Cost Encoders
 

These encoders aren't really the same as the s4. They're weather sealed and the shafts are supported by ball bearings. The price of an equivalent Industrial encoder corp encoders is 200$<.

Re: Low Cost Encoders
 

Giving fair warning to set expectations accordingly.
Several things have cropped up for this weekend that will delay my testing.

I am working on it but in addition to the other obligations I ordered something which may not arrive on Saturday as I expected.

I will post what I can as soon as I can.

Re: Low Cost Encoders
 

Yes, I do believe that there are companies who steal intellectual properties. My post was related to intellectual properties and not where it is made. It doesn’t matter who steals from whom, whether its US based company who steals from non US company or the other way around. The company that designs products invests lot into their design and testing. More over these companies spend lot in making sure that their product stands by their specifications and meets industry standards. I was a Design and Application engineer and I know what goes into a product development.

It’s naïve to think that this does not happen. Recent dispute between Apple and Samsung is one example. And just don’t forget the lady who got electrocuted with fake iPhone charger!

Before you vent your frustration, read the post and understand, my message did not mention anything about labor abuses. What “politics” are you talking about? My point is just plain and simple; before I put my money, I will do my best to make sure it does not go to thieves. It is not always easy or simple, but when someone is selling for half price, it raises a red flag!

This is :mad: for those who steal!

Re: Low Cost Encoders
 

Your argument is still without demonstrable evidence.
I will dismantle these encoders, post pictures and then you can make your case.

It is round, can like, has a 6mm shaft is not theft of anything unless you want to show me the design patent on that form. Surely quadrature encoding itself is not subject to any existing utility patent I am aware of. Prior art would be acceptable as evidence but for something as simple as the way that picture looks it really is pressing on the point of being a bit silly.

Once again without that evidence and without any patience to get that evidence you assume these are stolen designs. It's just not acceptable to me.

I too am an engineer. I have 2 patents pending. I too would be *quite* annoyed if someone anywhere just simply took my work. However I would not assume they did so.

All technology tends to be derivative. You can't blame a tire manufacturer cause they didn't invent the wheel. You can't blame V-Tech because they didn't invent the telephone. I think it would be very ungracious professionalism if one FIRST team went at another for shooting frisbee because they did to. People do arrive at similar solutions from different places all the time. It is not magic that so many teams use wheels to shoot frisbee. Should I be annoyed at that?

As far as Apple and Samsung is concerned that is an example of business usurping engineering and a patent system that is utterly broken. We've got patent trolls sitting on mountains of valid ideas that are trapped because they have *no intention* to use those ideas as anything but weapons against innovation. So even mentioning that is political.

Apple did not invent the GUI and neither did Xerox. That idea was military technology long before they used it.
Yet for a *very* long time Apple ran around accusing Microsoft of stealing their idea.
Really?

STEM means scientific method should have a very firm grip on this community.
If your concern is that this is stolen: wait for me to do the work for you to prove the point.
If your concern is that this is unreliable: wait for me to do the work to demonstrate that.
Doing this as you are is political plain and simple. You are not following scientific method.
You are trying to 'poison the well' with suspicion and allegation.
That sort of business is natural for humans but science has to be above it.

Re: Low Cost Encoders
 

Finally all the parts arrived:

So I have a 5V 4096 position per revolution stepper (it is geared down) with ULN2003 to be driven by an Arduino or the like.

A dual LS7366R quadrature encoder PCB to monitor the encoder outputs.
U.S. Digital sells this component I bought the PCB from SuperDroidRobots.com.

A ServoCity set screw hub for the stepper.
A ServoCity set screw hub for the encoder.
They are different size bores. The same 6-32 tapped bolt pattern.

The Chinese encoders to be tested.

Now I need to make a mount and wire this up.

Then I will have set up a realistic environment turning the encoder back and forth for an extended period of time.

I will be able to tell if the encoder is missing pulses because I will mount 2 limits at either end of the rotation (so it won't rotate all the way around).

I will program the stepper to rotate till the encoder hits a point just before the limits on either extreme.

If it misses (by any serious margin) it will smack the limit and an error can be recorded.

Leave that run for a good long time and eventually it'll exceed the entire service lifetime FIRST will likely ever ask of it.

Plus, of course, it gives me lots of time to record samples of the output waveform.

As the entire motion is under Arduino control various speeds of rotation can be tested.

It would be extremely unlikely the LS7366R would roll over or miss a pulse so it would be safe to say any error like that is the encoder or an electronic issue.

Re: Low Cost Encoders
 

Wow, it looks like a very thorough test. My test would be to see if it reasonably well, drop it out a window and see if it still works. ::D But I think your test is much better.

Re: Low Cost Encoders
 

Can you also report back on how much signal jitter there is or isn't when it's stationary. Sure a capacitor could easily address that, just want to know how stable the signal is.

Re: Low Cost Encoders
 

I was planning on posting the actual signal as sampled by my oscilloscope.
So hopefully you'll be able to get that from there.

Just to manage expectations I wouldn't expect this done this weekend.
With NASDAQ doing a dance yesterday I am a bit preoccupied.
However I will work on it this weekend even if I don't finish it.

Re: Low Cost Encoders
 

No worries, whenever you get to it is fine with me.
The oscilloscope signal sampling will be fine.
Thanks for taking the time and effort to do this analysis.

Re: Low Cost Encoders
 

Could I have a propeller chip monitoring all the encoders and send all the data to the cRIO, using only 1 i2C digital I/O, or would that be illegal to the FRC rules?

Re: Low Cost Encoders
 

Based on last years rules that would be legal.

***** Disclaimer *****
It's not a design approach I would use or recommend.
You have 2 single points of failure. The propeller chip, and I2C.
A failure with either one, and you lose all of your encoder data.
***** /Disclaimer *****

Re: Low Cost Encoders
 

Just be aware...

Since the Propeller is not interrupt driven there's a chance that at 2400 steps per rotation with a 20MIPS cog you might fall behind at high RPM. Unlike the ARM using an interrupt it won't generally freeze. It will just miss transitions.

I actually do have a Propeller based PropASC+ here.
For the sake of this test I decided against attempting this initially.
I know these quadrature chips work so I'd rather not introduce user code where I don't need to.
The code needed to do this in a Parallax Propeller is readily available.

I am still working on this. Also building a CNC machine. Also writing code for another project so bear with me. So far no major issues.
I'm a couple thousand into FIRST expenses so far this year so gotta keep all the things rolling.

Re: Low Cost Encoders
 

I don't want to rush you but I'll have a chance to make a order soon and I'm thinking of ordering a few. Any opinions so far?

Re: Low Cost Encoders
 

So far they work fine.

I have been swamped by unplanned (not always bad) excursions.
Hope I can commit more time this week.

The biggest issue I see so far is the unusual for FIRST resolution.
I will do my best to make sure to finish this month.
That will leave you 8 weeks to order and ship.

Re: Low Cost Encoders
 

Thanks, I'll wait.

Re: Low Cost Encoders
 

It's the end of the month. Any news?

Re: Low Cost Encoders
 

News: The sky is blue...sometimes ;)

Working on it but my day today is shot.
I won't let this go past the weekend.

Re: Low Cost Encoders
 

Re: Low Cost Encoders
 

LOL really? :rolleyes:

My money, my time, my priorities:
Start looking for my stuff tonight I spent the better portion of the weekend helping a friend's family in need.
It couldn't wait and I had little warning.

Now I am at work at my day job and (last I checked) we like our economy to stay working (then again we've all seen it lately ::ouch:: )

Re: Low Cost Encoders
 

I agree... More times than not you get what you pay for. Yeah, name brand encoders do cost a pretty penny. But the quality is excellent. The only time I've had a name brand encoder fail was back in 2011 when a US digital one was broken by a transmission removal mishap (I think, it's been a few years).

With cheapo ebay wonders, quality is of least concern. People will buy cheap parts because the parts are cheap. Not because of "silly" quality or warranties or customer service. Hence why with such parts if you get any of the three then you're lucky.

For a prototype, yeah, a cheap knockoff might work. But I'd personally avoid it on a competition robot. Murphy's law gives few mulligans. Especially during eliminations.

Re: Low Cost Encoders
 

I doubt that most people who claim someone else stole someone's product know the difference between a utility and design patent. A patent is the proper way to enforce these intellection properties. Simply asserting a design is stolen is inadequate. Especially when until now the only evidence anyone brought here was: it looks like an encoder.

The support issue is pretty irrelevant. In this economy most people are increasingly unlikely to get spare parts gratis and if the encoder is built properly for an application I wonder what support could be required or even needs to provided. It seems unlikey an encoder vendor is going to take the time to ship engineers and test equipment for a small purchase to hunt for an unusual problem.

Just making an optical encoder with a quadrature wheel is not a utility patent violation.
As far as the weakness of a design patent and how to enforce it Internationally that's a whole different mess and frankly that's the patent holder's obligation (so if you see something that is a direct ripoff please feel free to send them the pictures it is so not my problem).

So let's start with the high resolution pictures of the guts of these encoders.
The files are 7MB each so it took a very long time to upload over my phone (it's been uploading in fact since 1:00 AM EST while I attend to more urgent matters). There are more than the 25 pictures that are showing I am busy and I need to time clear them into the system.

I have much more data and more pictures this was what I had time for today.
For all those that claim this is probably stolen: you've got the pictures have a ball.
I really don't care who uses these or why I said I would do this and so I am.

My website for this sort of stuff

As far as low quality: look for yourself they are not paper mache

Re: Low Cost Encoders
 

Thank you very much, I appreciate it. We have a ton of bots we need to keep running for demos and at the price of encoders we usually remove them for our comp bot.

I still don't understand why people are calling this a knockoff, there's nothing new, innovative or proprietary about a quadrature encoder. Just because it comes directly from china does not mean its a stolen design.