How to and2 the probe input with a digital input
10 Oct 2023 21:32 #282706
by Waldemar
Replied by Waldemar on topic How to and2 the probe input with a digital input
Hi Tommy,
It's not a random issue now - I sorted out the grounding by connecting the 24VDC common neutral to the control box frame ground - I'm told that technically this is bad practice BUT all of the random triggers have disappeared along with the noise on the probe's cable when the VFD was running. (Generally speaking my box and the cables etc have been shielded pretty well.)
My issue (Probe tripped during non-probe move) happens only occasionally when the tip of the end mill is coming off the touch off surface - which will usually be a bit of scrap that gets faced off to correspond with work on the table.
And I totally agree with you, but this appears to be a problem that many senior forum members have faced and apparently solved in software. Take Andy Pugh's DIY probe - it still needed a software fix for the mechanical bounce and rodw suggests a couple of software fixes for the problem here:
forum.linuxcnc.org/24-hal-components/423...rrors?start=0#269052
and repeats the and2 fix here:
forum.linuxcnc.org/24-hal-components/423...rrors?start=0#217796
The issue I'm up against is not having the knowledge to be able to implement rodw's simple enough sounding advice:
You did ask for pics of probe and control box - they don't serve any real purpose as the noise issues are sorted and my question is really about modifying the .hal file, but here they are anyway.
Wal.
It's not a random issue now - I sorted out the grounding by connecting the 24VDC common neutral to the control box frame ground - I'm told that technically this is bad practice BUT all of the random triggers have disappeared along with the noise on the probe's cable when the VFD was running. (Generally speaking my box and the cables etc have been shielded pretty well.)
My issue (Probe tripped during non-probe move) happens only occasionally when the tip of the end mill is coming off the touch off surface - which will usually be a bit of scrap that gets faced off to correspond with work on the table.
Sorry to have to say this, but seeking software solutions for hardware issues is never ever a good idea.
And I totally agree with you, but this appears to be a problem that many senior forum members have faced and apparently solved in software. Take Andy Pugh's DIY probe - it still needed a software fix for the mechanical bounce and rodw suggests a couple of software fixes for the problem here:
forum.linuxcnc.org/24-hal-components/423...rrors?start=0#269052
and repeats the and2 fix here:
forum.linuxcnc.org/24-hal-components/423...rrors?start=0#217796
The issue I'm up against is not having the knowledge to be able to implement rodw's simple enough sounding advice:
and:When I faced this, I modified my probing gcode routine to set a digital output true from gcode and false after probing.
Then you can and2 the probe output with the digital output before connecting to motion.probe-input.
(I do believe that both snippets above relate to the same solution, just expressed differently...) What I'd dearly like to see is a snippet from somebody's .hal and/or gcode files with maybe a couple of pointers thrown in that give me a bit more of a chance to understand how to to set this up. Or is is that considered cheating?!When I had this issue I and2'ed the probe signal to a digital output and added m62-m65 to my probe routine so the probe would only trigger if the digital output was true (during probing).
You did ask for pics of probe and control box - they don't serve any real purpose as the noise issues are sorted and my question is really about modifying the .hal file, but here they are anyway.
Wal.
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10 Oct 2023 23:09 #282712
by tommylight
Replied by tommylight on topic How to and2 the probe input with a digital input
Skipping quoting and just chronologically answering, hopefully 
That should be grounded for noisy installations, always, all power supplies i had till 2016 had this tied to ground inside the power supply, some new ones do not but some still do.
Hell, even laptop power supplies with 3 prongs usually (again, before, always) have the 0V side tied to ground.
Even bigger hell, my Mazak has that tied to the case/chassis/all 3.5 tons of metal, uses sinking sensors/switches and stuff so everything goes to ground, worked with the original control, works with Mesa and LinuxCNC without issues.
All this is as i do not get it who would say that is a bad practice, except if there is no grounding anywhere and no option for providing it. Only in this case it might be better not tying it to ground as the chassis/case would act like an antenna.
---BUT, if you mean the neutral on the line power side, that is never ever a good idea. If this is not the case, please do not refer to" - or 0V or GND " as "neutral" ever, that sent shivers down my spine, bad sh1t can happen...
-
I do understand the confusion as this "internet experts" naming stuff at random to look smart has gotten out of hand, -V is negative voltage, 0V is common, +V is positive, that is it. Naming 0V as -24V is wrong always as power supplies can have negative voltages so for us in electronics seeing +24V and -24V is always 48V, naming it GND is OK only if it is actually tied to ground, but not dangerous or wrong per se.
Sorry for the long winded reply, but no neutral, please.
Juts to clarify, you mean the DC side 0V or - or GND side of the DC output, right?I sorted out the grounding by connecting the 24VDC common neutral to the control box frame ground - I'm told that technically this is bad practice BUT all of the random triggers have disappeared....
That should be grounded for noisy installations, always, all power supplies i had till 2016 had this tied to ground inside the power supply, some new ones do not but some still do.
Hell, even laptop power supplies with 3 prongs usually (again, before, always) have the 0V side tied to ground.
Even bigger hell, my Mazak has that tied to the case/chassis/all 3.5 tons of metal, uses sinking sensors/switches and stuff so everything goes to ground, worked with the original control, works with Mesa and LinuxCNC without issues.
All this is as i do not get it who would say that is a bad practice, except if there is no grounding anywhere and no option for providing it. Only in this case it might be better not tying it to ground as the chassis/case would act like an antenna.
---BUT, if you mean the neutral on the line power side, that is never ever a good idea. If this is not the case, please do not refer to" - or 0V or GND " as "neutral" ever, that sent shivers down my spine, bad sh1t can happen...
-
I do understand the confusion as this "internet experts" naming stuff at random to look smart has gotten out of hand, -V is negative voltage, 0V is common, +V is positive, that is it. Naming 0V as -24V is wrong always as power supplies can have negative voltages so for us in electronics seeing +24V and -24V is always 48V, naming it GND is OK only if it is actually tied to ground, but not dangerous or wrong per se.
Sorry for the long winded reply, but no neutral, please.
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11 Oct 2023 01:10 #282716
by Waldemar
To the right of the 24VDC PS I have the common positive & negative terminals that come off that supply. The earth on the AC side of the 24VDC supply (arrow 1) is connected to frame ground (arrow 2), and so is the green and yellow wire coming off the common negative terminals (arrow 3). Frame ground also has the earth coming in from the AC mains attached to it - and this is what I'm told is bad practice (DC and AC sharing earth). Having said that, connecting that 24VDC common negative terminal to the frame ground solved ALL of the noise issues that the addition of the probe & its wires had introduced.
Wal.
Replied by Waldemar on topic How to and2 the probe input with a digital input
Heh - sorry - no, I didn't mean that. See the attached pic.BUT, if you mean the neutral on the line power side, that is never ever a good idea.
To the right of the 24VDC PS I have the common positive & negative terminals that come off that supply. The earth on the AC side of the 24VDC supply (arrow 1) is connected to frame ground (arrow 2), and so is the green and yellow wire coming off the common negative terminals (arrow 3). Frame ground also has the earth coming in from the AC mains attached to it - and this is what I'm told is bad practice (DC and AC sharing earth). Having said that, connecting that 24VDC common negative terminal to the frame ground solved ALL of the noise issues that the addition of the probe & its wires had introduced.
Wal.
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