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Messages - Karl W

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General Mach Discussion / Re: Gcode more than 100,000 lines
« on: April 09, 2012, 02:31:44 PM »
I just ran a path with just under a million lines.

Around halfway through I encountered SEVERAL "limit switch activated" errors, even though the switches were clearly not activated. The machine was moving very slowly at the time so I was able to restart from position, but it kept faulting out every few minutes for a total of about ten times, then went on and machined the remainder of the part (another 500,000 lines) without a hitch.

I am aware that noise is often the culprit. I will check and reset the debounce to 2000 unless someone thinks another number is better.

Is there anything else I should change?

I am not getting watchdog errors.

I am using Tempest with its older Mach version. Ethernet smoothstepper plugin v10a. No errors from the ESS that I can tell.

In another part of the path, the X-axis stopped moving completely at one point, though it would jog on the screen. I do not think this was related, but I cannot be sure, because repowering the machine, rehoming and rezeroing fixed the issue. I thought it was a wiring issue, but all wires from the control to the motor showed continuity. It has never done that before.


SmoothStepper USB / Re: Ethernet SmoothStepper first test
« on: April 04, 2012, 01:24:28 PM »
OK the upshot of all this is that the porter Cable 892 basically stopped working. I had the bearings replaced for $50 and it died again, so I replaced it with a 690 and another 890 from eBay.

Overall I think the 690 is a much better built machine with a cast metal top bearing mount, rather than plastic, and a ground wire to the earth.

I am running another 890 with the alligator clip this time for the moment, until I can rig the SPID at which point I will switch back to the 690 for reliability. But the twin lead wire is a keeper; pretty easy to use.

SmoothStepper USB / Re: Ethernet SmoothStepper first test
« on: March 05, 2012, 06:35:31 PM »
Oh sorry I have been too busy in the garage and I missed Jeff's post.

Point by point then:

1. I take your point (but who is Will Robinson?). Fools rush in where angels fear to tread. I assume the PDMX will start to melt if the spindle itself goes hot, which should be a good clue that there is a problem. I suppose one of the hot wires to the speed control could somehow contact the end of the green wire where is is screwed to the bearing; this is indeed a safeguard that has been undone, because that ground wire attachment is up above the plastic housing for the bearing in the same vicinity as the powered wires.

2. I understand this - I think. The green conductor is no longer connected to Earth. It is connected to the PDMX common pin, and to the armature. Therefore I am not using earth ground as a return path; I am only using a wire that used to be connected to Earth ground to carry a low voltage signal back to the breakout board.

3. I am not using Earth ground on the wire from the spindle (see above). Yes the wire is in the same bundle as the power wires to the router. Fortunately the router is off when I am touching tools to plates, so I don't seem to have the noise problem that other people refer to, where the LED trips prematurely and the Z axis goes up before touching the plate.

All in all it sounds like running a new wire is a good idea, or perhaps just disconnecting the green one from the bearing and putting a clip on it to hook to the bit. I'll probably do that when the current eight hour machine run is done, and in the meanwhile I'll unplug the spindle when changing tools (thankfully there is a plug on the Z axis).

Thanks for the input and your concern,

SmoothStepper USB / Re: Ethernet SmoothStepper first test
« on: March 04, 2012, 11:36:00 AM »

Apparently a 0.01 microFarad capacitor between the input and ground helps; I will see if I can find one today and report back.

Correction it is 0.1 uF capacitor, not 0.01. It prevents accidental tripping of the sensor by noise in the circuit, but doesn't help with the grounding issue per se.

SmoothStepper USB / Re: Ethernet SmoothStepper first test
« on: March 04, 2012, 11:34:40 AM »
FYI for anyone trying to sort it out I think this Erniebro thread is pretty good on autozero, except the grounding stuff:


SmoothStepper USB / Re: Ethernet SmoothStepper first test
« on: March 04, 2012, 04:37:03 AM »

You don't want to try and use the machine itself as a current return path. Not only do all the bearings a sliding parts not make for a good conductor but if the machine is bonded to earth ground you are also running trying to run a low voltage return signal through earth ground (which is a bad idea all the way around).

I use a two lead cable with alligator clips. Clip one lead (the common) to the bit, clip the other to the part/tool touch plate.

I finally got it to work. Jeff it was your comment on some other thread about the breakout common voltage being different than the earth potential that put me on the right track. There is a lot of discussion about how you don't need a second wire if your machine is properly grounded, and I am here to tell everybody that is a load of poppycock.

The machine has a three wire power cord running to the spindle, which was connected to earth ground at the control box. Given that the spindle itself (PC 890) is double insulated and has no ground prong on its two conductor power cord, that ground wire from the control to the spindle was just sitting idle. There was no way I was going to run a third wire out there when I already had an unused one routed nicely through the cable carriers. Plus I could not find an alligator clip large enough to fit on a half inch end mill. So I took a few liberties.

1. I put a three pronged cord on the router and tapped the ground wire into the top bearing block with a #6 machine screw. This allowed me to shorten the cord also, which was overdue.
2. I took the other end of the ground wire (in the control box) off the earth ground and tied it to the breakout board common ground. There is still plenty of earth ground connection going on in the control box; the only thing I moved wasn't being used anyway. I am a bit nervous about some sort of stray voltage flying around inside the router frying my breakout board, but so far so good.

Now my LED lights flash on reliably when the bit contacts both plates.

There is much I still do not understand about what is getting pulled to what voltage; for instance the voltage at pin 15 stayed reliably at about 3.9V relative to earth whether it was shorted to common or not. Isn't it supposed to get pulled low? And now the plates register zero volts to earth at baseline, whereas I thought they should have some voltage on them until they are shorted to the tool, at which point they get pulled low.

But this is all academic as the autozero routine works fine now with Tempest, the 2010 screenset and ESS. I did have one issue where the Z homing limit switch was not working; this seemed to go away after I disabled "persistent DROs" and now it is working fine again. Some scary sounds came out of that little stepper but I think it is OK.

I am really happy to have this feature functioning. However I am also amazed at how difficult it was to find the two or three threads that deal most fully with the issue, and how no one really seems to have discussed the fundamental aspects of "pulled high", "pulled low" etc., how resistors play into that, and why the breakout board common ground voltage is not the same as earth ground. I suppose it is all on Wikipedia.

Back to making dust!

SmoothStepper USB / Re: Ethernet SmoothStepper first test
« on: March 03, 2012, 06:07:46 PM »
Thank goodness for Radio Shack. Unfortunately the capacitor makes no difference.

Given that the machine side of the BOB is at a different voltage than the computer side, I'm wondering how people get their cutting tool to the same voltage as the breakout board common pin. This seems to be what it takes to light the LED up.

Perhaps I will have to run a separate wire from the board all the way out to the spindle.

SmoothStepper USB / Re: Ethernet SmoothStepper first test
« on: March 03, 2012, 03:17:51 PM »
OK if I short the plate input to the ground on the BOB I can get the LED on the BOB to light up and guess what - the screen LED comes on also.

Apparently a 0.01 microFarad capacitor between the input and ground helps; I will see if I can find one today and report back.

It is odd because the input is not tripping low prematurely during the autozero routine; it just won't turn the BOB LED on at all unless I short the plate wire to the ground on the BOB itself. I tried touching the common ground wire on the cabinet, and the BOB LED would not light up.  The BOB ground is wired directly to the power supply for the control, which goes to a ground plug in the wall and a rod jammed into the earth outside my garage. So I don't understand why the ground on the board is any better than the ground elsewhere inside the cabinet. Is my ground faulty somewhere?

Nothing I was doing before was lighting up the input LED on the PDMX BOB; looks like the Smoothstepper had nothing to do with it.

Comments still welcome.


SmoothStepper USB / Re: Ethernet SmoothStepper first test
« on: March 03, 2012, 01:51:01 PM »

Big trouble with touch probe input for a while, but it turned out the BoB was set up very marginal and not driving the ESS reliably. Wierd symptoms, but all gone now I fixed the setup.

I am having some issues with probing also. PDMX 132 BOB to ESS. Basically I cannot get the "Probe Active" LED to come on in Mach, unless I switch to "active high" on the ports and pins, at which point it goes green and stays green.

 I get 3.8V on the touch plates dropping to 0.3 when it touches the spindle. I get the same 3.8 voltage when I compare the plate to a ground plug on my extension cord, so the spindle seems well grounded, even though it is a PC890 and double insulated with a two prong plug. I do have a ground wire running to the spindle but it isn't doing anything at the moment.

Breakout board seems to be powering the plate well enough.
Spindle seems well enough grounded to trip a TTL
I have the touchplate hooked to pin 15 on port 1. Configured pin 15 in Mach to "active low" and assigned it to "Probe". Seems pretty straightforward.

I wonder if this is something to do with the Smoothstepper not seeing and relaying the input signal to Mach. In the ESS data monitoring screen there are two options with checkboxes for the input pins; I tried both ways for pin 15 (but didn't restart Mach or ESS). Is there some other config option I should be looking at? The PDMX BOB is opto-isolated and inputs are filtered. Maybe switching to a CMOS (Port 2 apparently) from a TTL input port would help, though the CMOS seems more particular about the voltages it needs to trip...

Any ideas? Kind of driving me batty. Thanks.

General Mach Discussion / Re: Trajectory planning and CV
« on: February 15, 2012, 09:28:07 PM »
I have similar problems, but in 3D.

I think you may wish to try Tempest. I have been trying it out. It is pretty slow in 3D but from what I hear should do well on a plasma table. It isn't supported so I have no idea how it would handle your torch height etc. Whatever is in the last beta is what you get. No feedrate override. Sort of crude but might be an improvement over regular mach for your purposes. You can download a copy from the Tempest thread on the Mach 3 forum. Sept 29 is the most recent one. Look for attachments on posts from Art.

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