I use pots on all of my machines. Generally I have 3 pots, FRO, maximum
feed and spindle override. The ADC is provided by an Arduino which
controls all of my front panel buttons and talks to LCNC via Modbus over
USB. I did put the code on the wiki many years ago but I just did a
search and couldn't find it again. There do appear to be a few other
Arduino Modbus examples out there. Doing it this way, my front panel
just needs one USB cable going back to the control computer. This page
<https://dereenigne.org/arduino/arduino-modbus-rtu-adc/> shows a simple
Arduino example that reads analog inputs and spits them out over modbus.
The MB2HAL module will handle the LinuxCNC side.
too many pots don't have an absolute zero, and they can creep the
machine if left enabled.
I can't say I have experienced any issues with creep. I have had pots
fail but if you use decent quality plastic track pots they last a very
long time. I find it quite handy being able to tell at a glance what
your feed rate override/spindle override etc is, no matter what LinuxCNC
is doing at the time.
The only issue I have seen is that it can be a pain to get the pots
initially synchronized. Halui seems to ignore pots until the first time
you move them.
Les
On 26/10/2018 09:25, Gene Heskett wrote:
Generally a Potentiometer, which will need an A/D in the interface to
read it. With an activate pushbutton so they time out. Do that in your
hal file.
Why? too many pots don't have an absolute zero, and they can creep the
machine if left enabled. One of the reasons I prefer the encoder, it has
receivers built into the mesa cards making the encoder simpler to hack
up the hal to use them, the machine stops dead when the dial stops
turning (might be some windup it has to use up first if you've spun the
dial too fast, so be ready to spin it the other way when its going to
run into something) and I still time it out in about a minute after its
last use. Safety, safety.
I use the encoder to set the jog size per count, all done in the hal
file, display the size of the jog per click in the axis gui using pyvcp,
a pusbutton enables that and the encoder dial is enabled when the button
is released, and a one shot to shut it all off about a minute after the
last "jog" move.
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