Author Topic: Comparing an Alps rotary encoder to chinese rip-off  (Read 5606 times)

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Offline BreakingOhmsLawTopic starter

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Comparing an Alps rotary encoder to chinese rip-off
« on: May 23, 2020, 09:10:08 pm »
Just a quick look at a comparison between a genuine Alps STEC11B13 versus a chinese rip-off.
Results as expected:

We'll start with just a 10k pullup:
Alps:
1-Alps-naked" border="0
Won-Hung-Lo:
2-Chinesium-naked" border="0
Wow...just..wow.. :palm:

Can that be cleaned with 100nF to ground?
Alps (just for comparison)
3-Alps-100n10k" border="0
Won-Hung-Lo:
4-Chinesium-100n10-K" border="0
That noise is still above the "high" threshold of most MCUs. Sure, you could fix that with more parts, but jeeez, why would you want to?
 
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Online ataradov

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Re: Comparing an Alps rotary encoder to chinese rip-off
« Reply #1 on: May 23, 2020, 10:03:02 pm »
I appreciate the existence of both. Sometimes price is important and I'm willing to sacrifice some performance for that.

Also, your case seems to be extreme. There is typically some bounce, but not that much. So picking the right cheap option is also important.

That is for new designs. If you are fixing something that was not originally designed to accept the noisier version, obviously replace with the real deal.
Alex
 
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Offline BreakingOhmsLawTopic starter

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Re: Comparing an Alps rotary encoder to chinese rip-off
« Reply #2 on: May 23, 2020, 10:35:38 pm »
Yes, this was a random pick from FleaBay. I got a bunch of these and they are all more or less the same, with a single one that is slightly better. This batch is practically unusable and i trashed it.
I like to have a cheap option too, that's why i do these benchmarks.
Just had to post this one for its spectacular fail, can't remember having seen such bad bouncing in 25 years of engineering. That thing is practically generating RF  :-DD 
 
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Offline james_s

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Re: Comparing an Alps rotary encoder to chinese rip-off
« Reply #3 on: May 23, 2020, 10:52:44 pm »
I'd be curious how they compare after both have had a few thousand cycles. I've had some good name brand encoders get really nasty with age, so it may not be a bad idea to use one of the cheap ones for development in order to get the software handling robust enough to tolerate the degredation.
 
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Offline ebclr

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Re: Comparing an Alps rotary encoder to chinese rip-off
« Reply #4 on: May 23, 2020, 11:01:29 pm »
You forgot to compare the price  :-DD
 

Offline BreakingOhmsLawTopic starter

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Re: Comparing an Alps rotary encoder to chinese rip-off
« Reply #5 on: May 24, 2020, 09:43:41 am »
Alps: €3,85/pc
China: €0,45/pc

There you go.
 

Offline Peabody

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Re: Comparing an Alps rotary encoder to chinese rip-off
« Reply #6 on: May 24, 2020, 02:30:30 pm »
I've found that taking encoders apart and cleaning them can sometimes improve their performance.  But the ones I've taken apart are all structured the same way.  There's a rotating contact that's dragged along a fixed contact during the closed period.  It's hard to see how that could possibly work as well as it does.  It seems that it should be a cam system which lifts one fixed contact away from another fixed contact, or lets it make contact.  You could still have bounce, but at least not dragging bounce.

Anyway, your scope pictures of the Alps encoder show better performance than any encoder I've seen.
 
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Offline CatalinaWOW

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Re: Comparing an Alps rotary encoder to chinese rip-off
« Reply #7 on: May 24, 2020, 03:36:34 pm »
Don't know what the package looks like, but if this was old equipment of any brand that I was trying to put back into service one of my attempts would be a shot of contact cleaner.  And it might be a good solution for using these things in hobby applications or possibly even short run, modest reliability requirement applications.  If the problem is just lack of contact lubrication or a poor quality dried up lube a good quality contact cleaner is not just a patch, but a repair.  If the problem is inappropriate metallurgy in the contacts or terrible surface finish on the contact ring you are right, just dump them unless you are a really strapped for cash hobby person.
 

Online SiliconWizard

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Re: Comparing an Alps rotary encoder to chinese rip-off
« Reply #8 on: May 24, 2020, 03:46:03 pm »
Won-Hung-Lo:
4-Chinesium-100n10-K" border="0
That noise is still above the "high" threshold of most MCUs.

Really? I can't see that from your scope capture. There is indeed some residual noise compared to the Alps one, but to me it looks significantly under the typical Hi threshold of a GPIO. Maybe there are some details I can't see from this image.

 

Offline Doctorandus_P

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Re: Comparing an Alps rotary encoder to chinese rip-off
« Reply #9 on: May 26, 2020, 05:30:08 pm »
100nF cap to GND is a very bad Idea.

It is also a common mistake lot's of people make.

Zoom in a bit on your scope, and then look at the discharge time of that capacitor, and calculate the current you draw out of the capacitor, while the switch is closing and may or may not be properly closed.

To limit the current to a safe value for the encoder, you would need to put a resistor in series of at least a few hundred Ohms to 1k.

I once had a 400MHz analog Beast of a scope which had flawlessly working optical encoders.
In my Rigol DS1052E replacement the encoders started failing when it was around 2 months old.
 

Offline BreakingOhmsLawTopic starter

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Re: Comparing an Alps rotary encoder to chinese rip-off
« Reply #10 on: May 26, 2020, 05:41:47 pm »
100nF cap to GND is a very bad Idea.

It is also a common mistake lot's of people make.

Zoom in a bit on your scope, and then look at the discharge time of that capacitor, and calculate the current you draw out of the capacitor, while the switch is closing and may or may not be properly closed.

To limit the current to a safe value for the encoder, you would need to put a resistor in series of at least a few hundred Ohms to 1k.

I once had a 400MHz analog Beast of a scope which had flawlessly working optical encoders.
In my Rigol DS1052E replacement the encoders started failing when it was around 2 months old.

It's 10k + 100n

 

Offline Doctorandus_P

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Re: Comparing an Alps rotary encoder to chinese rip-off
« Reply #11 on: May 26, 2020, 07:23:49 pm »
The 100nF cap is charged through the 10k resistor, so you see a nice RC curve on the positive flank.

On the negative flanks, the capacitor is brutely shorted, and discharged in a single pixel of the scope.
Ceramic caps can supposedly deliver up to 10A when shorted.
 

Offline BreakingOhmsLawTopic starter

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Re: Comparing an Alps rotary encoder to chinese rip-off
« Reply #12 on: May 26, 2020, 07:52:50 pm »
Yes, i see your point and you are right of course .
And I expect that adding caps is often the cause of fast deterioration of encoders.
That said, i expect an encoder to work out of the box as the Alps does formidably.
If you open quality encoders, you will find wipers that are separated into several contacts and sometimes even additionally staggered. All done so they don't bounce all at once, and the contact stays connected.
Cheapo encoders mostly don't have that. In fact, here is a picture of that bad example: single wiper contact as expected.
IMG-20200526-214810" border="0

And of course, the secret sauce is in the contact material.
 

Offline mikerj

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Re: Comparing an Alps rotary encoder to chinese rip-off
« Reply #13 on: May 26, 2020, 08:25:27 pm »
I once had a 400MHz analog Beast of a scope which had flawlessly working optical encoders.
In my Rigol DS1052E replacement the encoders started failing when it was around 2 months old.

Apples to oranges.  Optical encoders suffer very little in the way of wear, so provided they are sealed well enough I'd expect a long life.  Anything with wiping contacts is going to suffer wear with use.
 

Offline thm_w

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Re: Comparing an Alps rotary encoder to chinese rip-off
« Reply #14 on: May 26, 2020, 10:47:51 pm »
100nF cap to GND is a very bad Idea.
It is also a common mistake lot's of people make.
Zoom in a bit on your scope, and then look at the discharge time of that capacitor, and calculate the current you draw out of the capacitor, while the switch is closing and may or may not be properly closed.
To limit the current to a safe value for the encoder, you would need to put a resistor in series of at least a few hundred Ohms to 1k.

Its not clear if OP is just testing them or has them in circuit. Anyway, discussion here for anyone else curious: https://www.eevblog.com/forum/projects/bourns-encoder-filter-is-the-extra-r-useful-in-practice-are-the-values-good/ with relevant link on second page: http://www.ganssle.com/tem/tem387.html
Profile -> Modify profile -> Look and Layout ->  Don't show users' signatures
 
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Offline Jan Audio

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Re: Comparing an Alps rotary encoder to chinese rip-off
« Reply #15 on: May 27, 2020, 03:03:46 pm »
I buy the cheap one and replace with good one later.
Not going to pay price high as the alps for test projects.
Thnx for the 10K advice, i just use 100n, next project i try 10K.
 

Online MarkF

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Re: Comparing an Alps rotary encoder to chinese rip-off
« Reply #16 on: May 27, 2020, 05:28:31 pm »
Have you seen the PEC11 Series suggested filter?

997503-0
 
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Offline Jan Audio

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Re: Comparing an Alps rotary encoder to chinese rip-off
« Reply #17 on: May 28, 2020, 12:48:53 pm »
Are those extra resistors worth the space ?
That is 4 per encoder, gonna try 2 first.

Oh wait those are pullup-resistors, and i have those internal in the PIC, hmz.
So you need pullups disabled in the MCU for this one.
« Last Edit: May 28, 2020, 12:51:43 pm by Jan Audio »
 

Offline exe

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Re: Comparing an Alps rotary encoder to chinese rip-off
« Reply #18 on: May 28, 2020, 01:11:10 pm »
I had the same dilemma, and I ended up with just using cheap encoders. Motivation: it works fine, usability is not affected by this. I don't know how long they will last, will see.
 

Online MarkF

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Re: Comparing an Alps rotary encoder to chinese rip-off
« Reply #19 on: May 28, 2020, 01:23:44 pm »
Are those extra resistors worth the space ?
That is 4 per encoder, gonna try 2 first.

Oh wait those are pullup-resistors, and i have those internal in the PIC, hmz.
So you need pullups disabled in the MCU for this one.

Here is one of my PCB layouts:
I didn't crowd the parts and you could reduce the space.
All 1206 SMD.

 

Online SiliconWizard

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Re: Comparing an Alps rotary encoder to chinese rip-off
« Reply #20 on: May 28, 2020, 02:07:04 pm »
Have you seen the PEC11 Series suggested filter?

(Attachment Link)

That's what I have always used with rotary encoders.
 

Offline Jan Audio

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Re: Comparing an Alps rotary encoder to chinese rip-off
« Reply #21 on: May 28, 2020, 02:27:55 pm »
By the way : i have 100n caps, not the 10n.
 

Online MarkF

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Re: Comparing an Alps rotary encoder to chinese rip-off
« Reply #22 on: May 28, 2020, 02:35:12 pm »
By the way : i have 100n caps, not the 10n.

I believe that will be okay as long as you don't spin the encoder very fast.
 

Offline Yansi

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Re: Comparing an Alps rotary encoder to chinese rip-off
« Reply #23 on: May 28, 2020, 02:37:32 pm »
Are those extra resistors worth the space ?
That is 4 per encoder, gonna try 2 first.

Oh wait those are pullup-resistors, and i have those internal in the PIC, hmz.
So you need pullups disabled in the MCU for this one.

Yeas they are, as only uneducated designer connects  100nF large capas accross the contacts directly. It will wear the shit out of the contacts in no time.

Either filter completely in SW, or use a reasonable HW approach. (100nF across a finicky tiny mechanical contact is not one of them.)
« Last Edit: May 28, 2020, 02:39:45 pm by Yansi »
 

Offline Jan Audio

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Re: Comparing an Alps rotary encoder to chinese rip-off
« Reply #24 on: May 28, 2020, 02:56:19 pm »
What do you mean ?, without resistor the encoder will wear out faster ?
I dont see how.
 


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