UC100 maximum spindle index pulse per second?

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UC100 maximum spindle index pulse per second?

Postby gezzer » Tue Sep 10, 2019 11:01 am

Hello, I'm trying to setup UCCNC/UC100 for lathe usage, knowing the limitations. I have a Boxford TCL 160 that I'm retrofitting, it has an encoder disc on its spindle with 100 PPR for A/B and 1 PPR for index pulse. So I connected the axis stepper drivers, spindle pwm output and everything works fine until now.

I removed the original IR sensors on the encoder disc because the previous owner fried them because of a misconnection. I mounted 2 optical counters for A and B and 1 more for the index pulse. So for the test, I connected the 100 ppr A sensor to index input pin of my control board, set the index input prescaler to 100, and started the spindle manually with a known speed of 1000 RPM. The measured actual spindle speed on the UCCNC does not go beyond ~320 RPM an it is fluctuating. It's like it's missing some pulse inputs. I also connected the 1 PPR index sensor and repeated the test, with 1 PPR sensor the reading is accurate and pretty stable.

How much pulses per second does the UC100 support for index input and quadrature encoder A/B inputs? If there is a limitation for the encoder input frequency on UC100, i can cnc mill a new encoder disc out of aluminum, but i need to know if there is such a thing. I also don't want to lose precision while the original disc is a considerably nice 100 PPR one.
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Re: UC100 maximum spindle index pulse per second?

Postby cncdrive » Tue Sep 10, 2019 12:44 pm

The frequency cuts around 50kHz.
Usually the limitation is not the motion controller but the breakout board, especially if it has a slow optocoupler that often cuts the frequency at a few kHz.
Our breakout boards (UCSB and UCBB) both has super fast optocouplers, but chinese BOBs always have very slow ones due to low cost...
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Re: UC100 maximum spindle index pulse per second?

Postby Robertspark » Tue Sep 10, 2019 12:45 pm

Rob
Einstein ― “If you can't explain it to a six year old, you don't understand it yourself”
...working my way through the 1000+ ways things don't work to find the one that does
UC400eth, UC300eth, UCCNC v1.2110, Neuron Lite
UCCNC v1.2110 Macro Manual
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Re: UC100 maximum spindle index pulse per second?

Postby gezzer » Tue Sep 10, 2019 5:20 pm

Hello again, after hearing from you that UC100 is capable of 50 kHz, i borrowed an oscilloscope to see that the phototransistor output at the sensor was pretty slow. Around 1.5 kHz, the signal got so small that it wasn't possible for comparator on board to generate pulses properly. There was an SMD capacitor between the phototransistor output and the ground, i removed it and the signal is pretty much accurate and stable at 1100 RPM. I'll later test it on 3000 RPM.

Thanks for the info! By the way the anti-bot captcha at the forum registration was just hardcore, you shouldn't expect newbies to interpret G-code lol.
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Re: UC100 maximum spindle index pulse per second?

Postby cncdrive » Tue Sep 10, 2019 7:20 pm

Good to hear that you found the reason for the problem.
I think that capacitor was probably there for signal smoothing.

Haha, yes, the captcha is really powerful. So far this was the only captha on which spam bots did not get through.
Newbies should also understand basic g-code. At least on that low level which the captha asks, if not then they should learn it, because they will want to operate a CNC machine. So they will have to learn it anyways. :)
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