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#QMX Glitchy encoders? Not any more ?
#qmx
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My V1 80-20m QMX has had issues with a glitchy VFO encoder. It would often skip in the opposite direction to which it was being turned which made tuning a bit awkward and menu selection even more so.
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After taking the encoder out, dismantling it and cleaning the contacts, the issue was much better but still not great. I tried replacing the encoder with an AliExpress part that was linked in another thread but the A/B switch contacts were reversed on that one, requiring short jumpers to be run from the two outside encoder pins to the pads on the opposite side. Even then, those encoders were a bit pants (I tried a couple).
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On a hunch, I re-fitted the original encoder and soldered a 10nF SM capacitor from each of the two outer pins to the common ground pin. This has now completely cured the glitches and the encoder works smoothly and accurately. I can now tune accurately and step through menus in the order they're meant to appear. Happy Days ??
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I've attached a photo of the? bodge in case anyone else is having similar issues and wants to give it a try. If the photo doesn't appear, here's a link:
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Cheers,
Ronan
MM0IVR?
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Hi Ronan,
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Your post saved me. I have been struggling with a similar problem since I received my QMX last week. My QMX's symptom is to push left rotary(change mode/band) will freeze the QMX randomly. I have given the PCB a good alcohol bath and re-done some suspicious joints, but the freeze keeps happening. Upon read your post, I opened the schematic, and found there is a very convenient location(JP302 5-7) to add the "10p" cap. I have pushed the rotary for the whole morning and proofed the remedy is right.
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Now, my QMX is ready for the trails and mountains.
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TU es 72,
Wei, AG6AQ |
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Hi, Ronan Thank you for sharing this, I remembered that QCX has 10k pull-up resistors and capacitors to ground like on image attached. It is quite interesting solution for QMX. May be chip has resistors internally but maybe some experience add more details. On the other side, contact bouncing can be solved in software part, but adding capacitor and resistors definitely add more accuracy at least for VFO encoder. |
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Ronan, Manfred,
I don't think age has anything to do with it. My early (May 2023) Rev 1's had the glitch from the beginning. My Rev3, Rev 4, and QMX+ Rev 1 all have the glitch. It seemed to be worse with the earliest firmware.
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I have just put the 10 nF caps in and the glitches are completely gone! Before this mod, scrolling through the Menu steps were frequently skipped semi-randomly, especially when turning fast. Occasionally it would even go backwards.?
I have also seen unintentional double clicks with the 'Select' and 'Exit' buttons, so I wonder if caps on these might also stop these double clicks. I think I will try it.?
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73, Dan? NM3A |
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Glad that's worked for you, Walter. Job well done, Sir. The buttons on my rig behave well so I didn't add any caps to those.
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As for the encoders; They do deteriorate with age as the contacts become dirty/worn and the wipers lose their pressure. Some are sub-par from the factory and it sounds like that's what you've got there.?
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Cheers,?
Ronan
MM0IVR? |
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Thanks for this suggestion. I have never had problems with the QMX "Tune" encoder, but continue to have volume glitches on the Volume encoder: /g/QRPLabs/message/123019?p=%2C%2C%2C20%2C0%2C0%2C0%3A%3Arecentpostdate%2Fsticky%2C%2CVE7EA%2C20%2C2%2C0%2C106355942
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I hope to try this capacitor addition soon to see if it helps my volume control problem.
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Larry VE7EA |
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Hi all I'm interested to read about this modification.? In general I don't like hardware debounce of things,?including buttons and rotary encoders which are interfaced to a microcontroller:
In general where a microcontroller is involved, it ought to be possible to do debouncing in firmware. There's a right way and a wrong way to do this. The wrong way is with timers or filters which effectively emulate what capacitors did in hardware. The right way is with a state machine which eliminates bounce by ignoring repeat state transitions until the next in sequence is seen. The cost of a few capacitors is very small and certainly much less than the time I will spend on firmware. Adding them to the next PCB revision would be trivially easy and the cheapest solution. But I don't like it because I still think the firmware approach is most elegant. I think I can make improvements to the rotary encoder handling. Most importantly, any firmware solution can be easily applied to all 6,000+ QMX/QMX+ radios already out in the wild. Which after all, is one of the whole points of SDR in the first place.? Note that the QCX-mini has an RC filter on its rotary encoder signals. However as a point of history, this was NOT done to eliminate encoder glitches. Which is why there are no capacitors on QMX+. It was done for a completely?unrelated reason. There was an audible noise which could not be eliminated, it's something about the PCB layout or compact structure, in QCX-mini. Adding the RC filter eliminated the problem, for which no other solution could be found despite a lot of investigation.? In summary I think the problem (about debounce) is in my firmware, and the best solution is also in my firmware, not me adding capacitors to future PCB revisions.? 73 Hans G0UPL On Tue, Aug 6, 2024 at 10:18?PM Daniel Walter via <nm3a=[email protected]> wrote:
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Hi Hans,
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Yes, I completely agree that the firmware approach is a wise move and look forward to seeing how that develops. This was purely meant as a stop-gap solution to get my QMX back into a useable state after a fair bit of to and fro with various encoders and the frustration of constantly skipped steps.
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With the cap values used, the radio keeps up well with fast encoder rotations and doesn't seem to suffer any skipped steps.?
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On a side-note, I remember making a little tuning add-on for my original QCX "classics" that piggy-backed on the encoder and emulated its rotation at different speeds and directions based on the position of a pot. I was amazed at the time just how fast I could go before things got glitchy.
Here's a video of the box in action:
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Cheers,?
Ronan
MM0IVR?
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Yury SP2RM
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