Messages

4711

General Mach Discussion / Re: Shield grounded at one end only

« on: February 08, 2014, 03:09:39 AM »

But after all this I'm back at my original question which was why commercial ready made up cables have the shield connected at both ends. I guess it's either that or just one end so the designer tossed a coin and said - two it is

Ian,

I just checked a couple of USB cables that I have here and the PC Earth is not carried through like it is with LPT cables - with my USB cables it is the signal GND which is  carried through.

Tweakie.

4712

General Mach Discussion / Re: Shield grounded at one end only

« on: February 07, 2014, 06:36:28 AM »

Just my 2p’s worth…

Basically, in most countries, regulations for mains connected equipment provide that unless a product meets the ‘double insulated’ (or a couple of other) standards all metal parts that we may touch must be bonded to protective Earth.

With our CNC the LPT pins 18-25 are used as ‘signal GND’ and sooner or later, in our build, we connect them to Earth - this is where the potential problems with electrical noise start if we don’t follow the one ended connection rule for shields / screens.

Tweakie.

4713

General Mach Discussion / Re: Is "GND" in the manual Common and +5v on the ZP5A-INT breakout board? (please!)

« on: February 07, 2014, 03:09:50 AM »

It is not uncommon for a board to incorporate 'pull-ups' to +5V on all inputs. The limit / home / estop switches are usually 'n.c' and pull the input to GND so Mach3 is configured to have the used inputs configured as 'active high'. This way the used inputs are held at GND by the switches but when a switch is activated the input rises to +5V.

Hope this helps.

Tweakie.

4714

General Mach Discussion / Re: Mach3 quick review

« on: February 06, 2014, 06:05:09 AM »

Thanks Jim.

I think there are a great many of us Mach3 users here that would echo your comments. 

Tweakie.

4715

Post Processors / Re: post processor for pro/Engineer?

« on: February 05, 2014, 07:48:41 AM »

You need to contact PTC, Inc. (formerly Parametric Technology Corporation) directly to ask if one is available.

Tweakie.

4716

General Mach Discussion / Re: Abnormal Condition - Axis are not refered to normal condition

« on: February 04, 2014, 11:23:08 AM »

Excellent explanation and solution Cletus.

Tweakie.

4717

Show"N"Tell ( What you have made with your CNC machine.) / Re: 1/5th Scale V8 Blown

« on: February 03, 2014, 02:20:54 AM »

Beautiful work Steve.

I had been puzzling about the setup for machining the offset cranks but now you mention the 5 centres it all seems so obvious. 

Tweakie.

4718

General Mach Discussion / Re: Iissues with my cnc router

« on: February 02, 2014, 06:32:51 AM »

I start with the AC in and it reads 122v then I measure the output of the transformer I get xxv dc and when I switch it over to AC I get 53v so it makes me think did I buy a AC transformer instead of a DC transformer? Then I measure at the capacitor and I get 73v DC and then I try AC and I get 154v.

I am assuming you do have a full wave bridge rectifier between your transformer output and the capacitor ?

Tweakie.

4719

G-Code, CAD, and CAM discussions / Re: BobCAD/CAM

« on: February 01, 2014, 07:49:07 AM »

Excellent work Hood - that tool-changer certainly is slick.

Tweakie.

4720

General Mach Discussion / Re: Mach3 Errors And Bugs

« on: January 31, 2014, 03:11:10 AM »

Just a guess but I would suspect an electrical spike (noise) is being created when your torch fires and this is upsetting your PC.

Try disconnecting the torch and THC then running your GCode again to see if the problem persists.

Tweakie.