Visit Us On FacebookVisit Us On TwitterVisit Us On Google PlusVisit Us On LinkedinVisit Us On YoutubeCheck Our Feed

Owon DS7102 – Rotary Encoder Noise Malfunction Fix

Hello All!

It has been a while since my last post. I had a lot to do all these days so my spare time was really cut down. In this post i'm going to write a small how to on how to fix possible rotary encoder problems on your OWON SDS7102 Oscilloscope. 

The issue:

Today while i was trying to read an analog signal using my OWON SDS7102 scope i realised that the Volts/div rotary encoder of Channel 1 didn't work as suspected. By turning the knob the value was jumping steps or do nothing ro changing direction. For example if channel 1 was set to 2V/div and the volts/div knob was turned one step right the value was jumping to 50V/div or to 20mv/Div or to another random value instead of 1V/div. 

In an older post i was analysing how a rotary encoder works. Brinking that post to my mind i thought that may be there is a filtering issue and the mcu reads most of the noise coming out of the encoder as a real output.

As a hardware engineer i always like to tear down the devices and see what is really going on inside. So i did and i reached the keyboard pcb.
OWON screws

After removing the backside of the scope you only need to unscrew the 5 screws shown in the above photo in order to reach the keyboard. 

Owon keyboard pcb backside

And… this is the keyboard back side. What i did was to solder two 100nF on each rotary encoder (one on each output) to filter the output signal. Each encoder has 3 pins in a row. The one in the middle is the GND and the other two on the sides are the outputs. As you can see in the above photo in the first raw i have soldered through hole capacitors and on the other two rows i have soldered SMD. Both types do the job and it's on your choice. 

After the reassembly of the oscilloscope i made a test and i show fully improved behaviour of all the knobs. The capacitors solved the problem and increased the quality of the knobs.

The conclusion is that the Chinese manufacturer may had chosen to make a software filter instead of adding these capacitors to reduce the cost but the software finally wasn't that good to filter all the noise. By adding these capacitors we reduced the noise going to the mcu from the rotary outputs and make software filter life easier. 

Now you can understand how important are the capacitors!

10 Comments

  • Tomas Kopriva
    25/12/2015 - 22:51 | Permalink

    Thanks for sharing .. i have had the same problems with my scope, with "knob board" of version 2.3. Your solution did work like a charm 🙂

  • Daniel
    29/05/2016 - 14:58 | Permalink

    Dear Haris, I had the same problem with this scope, it was really annoying. However, my vendor offered me a replacement keyboard (before I found your blog) when I asked about this problem, and with the replacement, the problem is gone for now. So it seems not all of the encoders have this problem. On the old board, the encoders had an "Everbest" (how ironic) trade mark, the new ones are labelled "LJV".

    Just wanted to share this because I still think this is quite a good scope for the money (in spite of some software issues), but this encoder behaviour got me really frustrated. So people who buy this model new now hopefully get the working encoders.

    And if the new encoders still fail too early, I will definitely try your trick with the filter capacitors.

    By the way, my boards (old and new one) had the version 2.3 on them, so obviously they did some re-design of the board, but this did not affect the encoder issue.

     

  • Dennis
    09/06/2016 - 20:03 | Permalink

    Awesome! I tried this on the horizontal position encoder and it did get significantly better, although still not perfect.

  • Steve Siegel
    25/08/2016 - 22:20 | Permalink

    Hi, I had a similar issue with an Owon scope. I made a test jig with a pair of LEDs. At first, the encoder was intermittant with random connections. After a while, it started working properly.

      My guess; The logic circuits do not impose enough current on the contacts to keep them "wiped" and by adding the caps, the instant current they produce being discharged is enough to keep the contacts cleaned.

      Just my thought, I am adding the caps you suggested to avoid having a repeat.

     

      Thanks for the article.

    • Marvin
      19/02/2017 - 00:13 | Permalink

      Adding to the problen is the fact, that the rotary encoder seems to be integrated in a key matrix to save pins. So you have no static state for the encoder switches… If the "rowscan" and the state change of a rotary encoder switch are to close, they could "miss". The little capacitance seems to hold the state just long enough to mitigate the problem 🙂

  • Girts
    26/10/2016 - 09:08 | Permalink

    Thanks for the tip, adding the caps seems to have fixed the encoder jumpiness for me!

  • Marvin
    19/02/2017 - 00:09 | Permalink

    Hi I just tried the fix with a V2.2 Button Board. The 100nF didn't work that well, but with 220nF it's stable.

  • Paul
    25/02/2017 - 03:45 | Permalink

    Thank you for this article. It fixed the issue of the rotary knobs. After 2 years, the DS7102V's rotary knobs were very difficult to use. So, like you did, I added these 100nF caps and now it's a lot better (but not perfect though). I'm really happy with the result.

    I would like to share two tips that could help when disassembling the backside of the scope :

    -The push button for on/off on the top side can be removed by pulling it. I recommend to do it otherwise, you might break a plastic part which is difficult to glue afterward (Trust my experience …) 

    -There are two others screws which are not visible in the first picture to remove on the left in order to remove the circuitry. These make a total of 7 screws to unscrew.

    Thank you again for this article.

  • Chip
    02/05/2017 - 16:45 | Permalink

    Add me to the list of happy users!  Mine was lousy from day one and only got worse.  Now the encoders work like a real scope.

  • Leave a Reply

    Your email address will not be published. Required fields are marked *