Author Topic: Rotary encoders go Bad?  (Read 6838 times)

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Offline johnnyfp

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Rotary encoders go Bad?
« on: May 31, 2012, 02:00:31 am »
Can rotary encoders go bad?

I've taken apart my UT2025B Oscilloscope because all the small dial rotary seem to miss steps or jitter back and forth when I turn them. They are a smooth step variety. While the big dials of a click type do not miss steps or jitter.


I've included some snapshots of the board. This board is controlled by an ATMEL AT89C2051, maybe hackable.  And the smaller chip is a HC574 D-Type Flip-Flop.

What I find strange is that all the output from the encoders have a Diode. Is that normal?

Cheers
Jfp
 

Offline free_electron

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Re: Rotary encoders go Bad?
« Reply #1 on: May 31, 2012, 02:26:57 am »
Yes mechanica
 Encoders do go bad eventually. Even optical ones ( dust, or the led that dies . Some optical ones use an old style lamp...)
The diodes is because the scan the rotaries together with the keys.
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Offline johnnyfp

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Re: Rotary encoders go Bad?
« Reply #2 on: May 31, 2012, 02:32:24 am »
It's not that old. And only lightly used. And I mean really lightly.

And all four of them at the same time.  Seems dodgy to me.

I'll try replacing one and see what happens, but it's interesting about the scan bit. I'm going to have to trace this board see what the circuit is. I didn't think that there was enough fidelity to do rotary and keys at the same time.

Jfp.
 

Offline free_electron

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Re: Rotary encoders go Bad?
« Reply #3 on: May 31, 2012, 04:58:24 am »
Yes there is. They probably have the commons tied to an interrupt pin... The moment they trap aninterrupt it means one is moving... Al that needs done is perform a fast sweep of he io to see which one is active ( there will be only one ). And them they read the other pin of that encoder. If it is low : left , high: right.

Pretty simple to do. Ive done complex frontpanels that way. I often multiplex the commons with the lcd display. Whenever the display is idle i use the datalines for scanning the keypad and encoders. Humans are slow anyway.... Cpus are fast.
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Offline typeglob

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Re: Rotary encoders go Bad?
« Reply #4 on: May 31, 2012, 01:32:16 pm »

I have one of these (Dave Smith Instruments Poly Evolver) and it has about 70-80 encoders. After a while (even with limited use) they start going bad and start getting really erratic. I can treat them with DeoxIT and that does work for a while, but in the end they get erratic again.

A few hundred of those synthesizers (and the related Prophet '08) were made and they all pretty much ended up with malfunctioning encoders. It probably cost the (small) producer quite a bit of money to placate furious customers (and some image damage to boot). They've switched to pots a while ago, even though encoders (arguably) make more sense for this type of application.

Ofcourse issues like these are in no way limited to one producer of goods. My Waldorf Blofeld synthesizer has 7 encoders and they have problems, my (rather expensive) coffee maker has one encoder and it has issues, etc.
 

Offline free_electron

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Re: Rotary encoders go Bad?
« Reply #5 on: May 31, 2012, 01:40:32 pm »
Much has to do with mechanical construction.
If you have an alps, panasonic or bourns encoder these will work years without problems.

If its a 1/2$ wing-fang-pong ...
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Offline tesla500

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Re: Rotary encoders go Bad?
« Reply #6 on: May 31, 2012, 03:54:07 pm »
I've found that MC Chemicals Super Contact Cleaner with Poly Phenol Ether is very effective for keeping encoders working well. Poly Phenol Ether (PPE) is a very stable oil that stays on the contacts and prevents oxidation. It's also good for keeping pots from getting scratchy.
 

Offline johnnyfp

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Re: Rotary encoders go Bad?
« Reply #7 on: May 31, 2012, 08:08:54 pm »
Yeap, it was the encoders. I replace them all and now they are working great again.

But what shocked me was that all of them died more or less at the same time. Seems that there was built in obsolescence done by the manufacturer. Lets hope these one last a little longer than the stock ones.

Now after this debacle I am wondering is my home lighting system is going to need a change in the design, as I'm using mechanical encoders for the Dimmer functions. And that's around 20-30 of them around the house!

Jfp.
 

Offline david77

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Re: Rotary encoders go Bad?
« Reply #8 on: May 31, 2012, 08:18:57 pm »
Even Alps can have a bad day. There's this infamous Blaupunkt/Philips car radio that Audi and VW put in their cars some years ago. They've all got Alps encoders in them and most don't work properly anymore...
 

Offline johnnyfp

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Re: Rotary encoders go Bad?
« Reply #9 on: May 31, 2012, 08:20:43 pm »
Funny you should say that. I have a alps car stereo and it's rotary encoder on the volumn is dying too.

Jfp.
 

Offline SeanB

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Re: Rotary encoders go Bad?
« Reply #10 on: June 01, 2012, 05:09:54 am »
I have one of those radios...... Still working though, though there are times when it only will go up in volume. Just move slowly then and all ok. I did spray some lube into the back of the encoder to redistribute the grease. Worked for a long time.
 


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