Tachometer Issues (Can't Deal With High Speed)

[GeckoSub]

So, before I do some drastic changes or start buying new hardware I wanted to ask here for ideas.

The tachometer on the H5 is fine up to around ~1600 rpm but if I increase the speed from there it's like the tacho gets overloaded and drops down to about 300rpm.
I am using a 600ppr encoder but it's geared 2:1 so it sees 1200ppr.
I think my spindle maxes out at around 2500rpm.

If this had been a real Omron it should easily be able to handle these numbers but maybe a cheap Chinese clone can't?
It's not an ESP32 limitation, right? Anything in the code that could explain this behaviour?

I may have a timing belt long enough to try a bigger pulley on the encoder so as to get to a 1:1 ratio and the "true" 600ppr of the encoder. Is that the smart, next move?

[GeckoSub]

I think I solved it - I am seeing the full speed now:

First, I tried another encoder I had but that one was even worse. Then I tried grounding both encoders which presented its own gremlins.
The solution was to go 1:1 on the pulleys as even the "good" encoder was crapping out spinning at +3000rpm (1500 at the spindle). Didn't take long to make the new pulley on the resin printer:

And I cut my first test threads:

Both of them are a bit "undersized" - especially the Delrin one. But the alu one is not too shabby (M8x1.25):

And this was done with no X-motor but my modified FW where at the end of each cut, the carriage dwells until I press "play" again. It works well so far and the X-DRO really helps, too:)

That said, I do have some EFI/ground loop/lack of grounding issues. E.g. if I ground the encoder shield to the machine, the encoder counts even when nothing is spinning. And when the lathe is running these extra counts get added to the real ones. But that's for future me to deal with...

Thanks Max for this awesome project!

[kachurovskiy]

Hey @GeckoSub, glad it worked out, sorry for not responding quickly, been doing a lot of driving lately.

[GeckoSub]

Hey @GeckoSub, glad it worked out, sorry for not responding quickly, been doing a lot of driving lately.

No worries:)

When you have time, do you think this issue was an ESP limitation or just the encoder itself not being able to keep up?

[kachurovskiy]

I'm not sure why would this happen, perhaps there's something in the code we need to tweak to adapt.

[GeckoSub]

I'm not sure why would this happen, perhaps there's something in the code we need to tweak to adapt.

Admittedly, I didn't try to replicate the issue on your stock FW... Let me try that in a day or two. Also, would be a good test to see if I got the RXTX splitter switch and USBTTL adapter set up correctly. The idea is that I flick a switch and move the USB-C cable to a second port on the panel for tft updates vs ESP reflashing. This, if it works, is a nice addition for people who tinker with the screenset and want to update it easily.

I'll report back:)

[GeckoSub]

Turns out, the new USBTTL adapter I put in the panel doesn't work so can't reflash the Nextion. Not sure if it's a wiring issue or what, but won't have time to look into it for a while. Will keep this open and report back once I get around to it.

If the encoder high speed issue is present in the stock FW, it would make sense to get it looked at but don't want you to waste time until we have confirmed it:)

[kachurovskiy]

During very high RPM there's probably not enough current to bring the encoder signal lines up to 5V and the signal becomes more and more flat until it stops triggering the PCNT. We don't use external pull up resistors on encoder lines and internal ones are very high resistance. Solution here would be to add e.g. two 2kOhm resistors from A and B encoder signal lines to 5V.

[GeckoSub]

During very high RPM there's probably not enough current to bring the encoder signal lines up to 5V and the signal becomes more and more flat until it stops triggering the PCNT. We don't use external pull up resistors on encoder lines and internal ones are very high resistance. Solution here would be to add e.g. two 2kOhm resistors from A and B encoder signal lines to 5V.

Thanks for that info Max:)

I know I said I would try to replicate the issue on the stock FW, but now I am not sure when/if I will get around to actually checking this out further. My apologies.
The thing is, I really liked this whole endeavour but I also need to get back to some other work/project that I have neglected.
I do want to give my custom FW 1-2 more small changes but as it is now, it seems to work.

As for the encoder/tacho issue, if others run into it, trying the resistor fix seems easy. But also, running a larger pulley on the encoder does the job and may be be better in the long run for the encoder bearings.

BTW, here's a short, simple video of the semi-auto threading and X-DRO working on my machine - this was all I ever wanted, haha:
https://www.youtube.com/watch?v=mqABSTqvwwI&feature=youtu.be

I will probably shoot another longer video showing the screenset and features of a bit better once I have the final panel and enclosure done.