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Shielding Issue and Mach3
« on: June 30, 2009, 02:38:56 PM »
Hey Mach3'ers,

I'm new, but learning quickly.

I built a 4 axis CNC Router Table 4.5' x 8.5', installed mechanicals, electronics, wiring, router, computer and Mach3/Lazy Cam software. I've been working toward perfecting the setup in conjunction with Tutorial Videos. I'm running limit/home switches in series, hence NC w/5v constant. I have an E-Stop that is NO. The diagnostics show pins are green on the parallel and lyellow ed's from my switches are out. So here's the configuration... X pin 15, Y pin 13 and Z pin 12 and all share common 5v wire.

When I have the limit swtiches selected for active and plug in the power supply for the motors I immediately get a limit switch message and an E-Stop condition, but no LED's are lit except for the solid green inputs from the parallel port which I believe is as it should be. Even so, resetting doesn't cure the problem as the message again shows a limit switch activated.

If I unplug the power supply for the stepper circuitry and manually trip the switches, the yellow LED's light up with the corresponding Axes indicating that I've configured and wired switches properly.

So then I deactivate limit switches to begin checking whether I can reference home. What happens is, the steppers begin moving Z towards home, but before reaching the switch, Mach3 changes movement to Y-axis and same thing happens, before hitting the home switch for Y Mach3 switches to X/A (actually only X is moving even though I've changed the button to RefConfigure( 9 ).

I believe there is enough noise coming from the Power supply wiring to the break out board and steppers to affect signals from the limit/home switch wiring which is constant 5v feed since it is NC.

My question is, What exactly needs to be shielded to prevent the "noise" from dropping the voltage which triggers limit/home switch signals? Or, is there an entirely different problem here that I'm not aware of since I'm relatively new to this stuff?

Unfortunately, i've used 18 gauge stranded unshielded wiring for all runs for the sake of saving cash on the initial build.

I've been pouring through the posts searching for similar problems but have not found anything like I'm experiencing.

Thanks,

Don

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Re: Shielding Issue and Mach3
« Reply #1 on: June 30, 2009, 08:15:13 PM »
First thing to try is set a value in the debounce.  Found in the General Config.

Start with about 3000 and see what happens.

If this fixes it then lower the value to lowest reliable setting.

This may well be all you need to fix the problem.

Greg
Re: Shielding Issue and Mach3
« Reply #2 on: June 30, 2009, 08:26:07 PM »
First, you have things wired backwards from the way I would do it.  E-Stop should *always* be wired NC.  Otherwise, if the switch fails, you won't know until you need it, and it doesn't work.  The Limit/Home switches should be wired NO, so they pull the BOB input to ground when the limit is reahced.  They should also have stiff pullup resistors on them, so it takes a reasonable current to pull the lines low.  *All* the signal wiring should be shielded, with the shield grounded *only* at the BOB end.  *All* grounds in the system should connect to a single point, preferably on some hefty metal piece, like an enclosure.  Never, ever daisy-chain ground or power connections.  Use the de-bounce in Mach if you have to, but I'd first get the signal quality cleaned up as much as possible, and use the debounce as a last resort.

Regards,
Ray L.
Regards,
Ray L.
Re: Shielding Issue and Mach3
« Reply #3 on: June 30, 2009, 08:52:11 PM »
Thank you for replying Greg.

Sadly, changing the debounce had no affect what so ever. As soon as power is applied to the breakout board, controllers and steppers the message "limit switch triggered" begins flashing and an emergency state is present. I reset and within 2-3 seconds another message "limit switch triggered" happens. I carefully installed all the wiring and rechecked to make sure there are no shorts. Again, in diagnostics, the green LED's are lit indicating a signal from the parallel port is present and no yellow LED's are lit for the limit switches.

Any other thoughts?

Also, HimyKabibble ... I appreciate the input... I wired the limits normally closed since it was part of the instructional video as the "safest method" to use, Also, it allows me to run home and away limits in series since I am limited in the number of inputs on my parallel port. The break out board only has one hook up for one parallel cable. As far as running separate wiring for the 5v's that's no problem.

Now to the shielded cable, what size would you recommend for the signal wire? 22, 20, 18 gauge? Solid core or stranded?

And, excuse my ignorance of acronyms, but what is a "BOB".

Thanks for the help,

Don
Re: Shielding Issue and Mach3
« Reply #4 on: June 30, 2009, 09:34:31 PM »
Thank you for replying Greg.

Sadly, changing the debounce had no affect what so ever. As soon as power is applied to the breakout board, controllers and steppers the message "limit switch triggered" begins flashing and an emergency state is present. I reset and within 2-3 seconds another message "limit switch triggered" happens. I carefully installed all the wiring and rechecked to make sure there are no shorts. Again, in diagnostics, the green LED's are lit indicating a signal from the parallel port is present and no yellow LED's are lit for the limit switches.

Any other thoughts?

Also, HimyKabibble ... I appreciate the input... I wired the limits normally closed since it was part of the instructional video as the "safest method" to use, Also, it allows me to run home and away limits in series since I am limited in the number of inputs on my parallel port. The break out board only has one hook up for one parallel cable. As far as running separate wiring for the 5v's that's no problem.

Now to the shielded cable, what size would you recommend for the signal wire? 22, 20, 18 gauge? Solid core or stranded?

And, excuse my ignorance of acronyms, but what is a "BOB".

Thanks for the help,

Don


BOB = Break-Out Board.  Wire gauge/solid/stranded is irrelevent - except any wires subjected to flexing as the machine moves MUST be stranded, the finer the better.   These a low current/low voltage signals, so any wire will work.  NC limits are OK, but I would still put a stiff pullup resistor (like less than 300 ohms) on the BOB input, and let the switches pull the signal to ground.

Regards,
Ray L.
Regards,
Ray L.
Re: Shielding Issue and Mach3
« Reply #5 on: July 01, 2009, 10:25:51 AM »
Looks like I'll have to bite the bullet on this one and rewire. That's going to take some time. Hopefully shielding the wire will take care of this.

At any rate I was able to get some things accomplish... heres one: http://www.brightstarlinks.com/006%20cropped.jpg
Re: Shielding Issue and Mach3
« Reply #6 on: July 01, 2009, 11:27:28 AM »
Looks like I'll have to bite the bullet on this one and rewire. That's going to take some time. Hopefully shielding the wire will take care of this.

At any rate I was able to get some things accomplish... heres one: http://www.brightstarlinks.com/006%20cropped.jpg

Hey!  Are you giving us the bird??  :-)
Regards,
Ray L.
Re: Shielding Issue and Mach3
« Reply #7 on: July 03, 2009, 10:54:11 PM »
Naaaahhhhhh... I wouldn't give anyone the bird unless they ordered and paid in full for one.

Well, completed the rewiring with shielded cable and ... have successfully shielded against the extra noise that the limit switch wiring/E-stop wiring was picking up causing all kinds of problems.

Now I can do a reference home all with limit switches active.

BTW, I used 22gauge two conductor limit switch wire. I wired each axis (two switches home and away) in series. It was a total of 5 runs including E-stop and Probe wiring.

Thanks for the help.

Best regards all,

Don