andre tchmil

Rotary encoder behavior. question for experts
« on: April 14, 2010, 06:03:18 PM »
guys ,
I have a CD player here that needs some attention.
The track selector goes with a rotary encoder to a 74H191.

this is the component:http://www.megatron.eu/SMC3/plugin-transformer?trafo=PDF&plugin=doc&mode=designin&method=GetFolderInfo&tp_subRulesID=1206567953264&webdavID=1236091592943&language=de&objType=doc

Is there a way to simulate the pulses from the encoder going to the logic IC ?
I don't have any schematic and I want to be sure before I order an expensive piece like that .


sahib

Re: Rotary encoder behavior. question for experts
« Reply #1 on: April 14, 2010, 07:11:25 PM »

Yes.

Using square wave output of your signal generator. If you do not have one then you can certainly make one using 555.

What is the problem?

gyraf

Re: Rotary encoder behavior. question for experts
« Reply #2 on: April 15, 2010, 01:05:21 AM »
You will need two square waves, 90degrees phase offset from each other. +90 or -90 degrees will determine rotary direction. For a crude sub, you can use two momentary push buttons..

Jakob E.
..note to self: don't let Harman run your company..

andre tchmil

Re: Rotary encoder behavior. question for experts
« Reply #3 on: April 15, 2010, 04:56:27 AM »
No signal generator here, but I guess some application on my laptop will work.

Are the square waves produced by that rotary encoder itself , or does it drive some chip on the PCB ?

Unfortunately I don't have any schematic for the CD player  ( EMT 981 )

sahib

Re: Rotary encoder behavior. question for experts
« Reply #4 on: April 15, 2010, 07:53:19 AM »
You are still not telling us what the problem is.

Square waves are produced by the rotary encoder and that is the whole purpose of an encoder.

Internally it has a thin metal disc with a number of apertures cut out.  The number of apertures determines the resolution of one full revolution. A TX/RX opto reads each aperture and the circuitry attached to it produces clean square pulse train depending on the number of apertures detected. Some times a second single aperture is also included to indicate a one full revolution.

You count the number of each pulse and determine the number of revolution and/or the angle of the shaft. Or the distance travelled. It all depends where and how you use the encoder.

Obviously this is in one direction. To detect the reverse motion you need the same pulse train but in opposite phase.

Although in German, look at the table Elektrische Daten on the link you gave. First column gives you the number of pulses the encoder produces. This is normally indicated on the product code. Second column gives you the number of channels which are opposite in phase. Third column is the operation frequency and the final two are the operating voltage and current consumption of the encoder.

 


andre tchmil

Re: Rotary encoder behavior. question for experts
« Reply #5 on: April 15, 2010, 09:10:34 AM »
thanks for jumping on board.
Problem is I can only select tracks in ascending order, no matter how I turn the encoder.
So it goes from first to last track , then locks there.

sahib

Re: Rotary encoder behavior. question for experts
« Reply #6 on: April 15, 2010, 09:44:20 AM »

You are welcome.

That means you are only able to read in one direction. I am not sure what you mean by saying how you turn on the encoder. Have you removed it?

If the encoder is reading in one direction, it is highly unlikely that it won't in opposite direction.

Did you check below?

The reverse button is working.

No problem on pin soldering.

No cracks on tracks between the control (whatever) IC and the button.

Check vias (where the track links from the bottom to top layer of the pcb) closely.

Use a magnifier and go over and over methodically.





 

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