USB Cable Question

[ATX Poly Products]

I have a PRS 48x48 Standard with the new style control box. My question is how good of Quality is the USB cable that comes with it and is it worth upgrading? Also how is it attached in the control box as I can't see the connection behind the input board?

I have been through Grounding the machine, Hubs, ect...

But I still get a comm error every now and then. Never while running a cut file but sometimes during going between a c2 command, K command, or from one file to the next...

Thank you for any help given...

Adam

[ken_rychlik]

Do you have it installed with a usb hub or plugged straight into your pc?

[ATX Poly Products]

I have tried the one that came with the bot and one from staples but they both seem generic....

What do you think about this one? It looks robust and much better suited for being in a shop....

http://us.startech.com/product/ST4300USBM-Mountable-4-Port-Rugged-Industrial-SuperSpeed-USB-3-Hub

[ken_rychlik]

I think that one is overkill.

Do a speed test. Under utilities, Diagnostic tools, choose speed test.

You are looking for 70% or better.

The ammount of ram on the pc makes a difference too. What do you have there?

[ATX Poly Products]

The speed test is around 72%...

I am still curious about the cable itself.

Connection at the control box-
Quality of the cable-

[frank134]

I have try a couple of the super usb hud. I found that on some I couldn't even get a connection or I lost it. The ones that work the best seem to be the cheap one . also on computer don't go high end. same. thing lost or couldn't not get the connection. It seem that shopbot like middle of the road equipment. this is stuff i actualy try. seven differance computer from windows xp to window7. XP work the best.

[dana_swift]

Adam, I am nervous about getting deep into the answer of what kind of cable and why. Here is the plain English version:

Mostly USB needs to be three conductors and a shield, or four and an shield. The data + and - should be a twisted pair within that shield. Beyond that it mostly needs a strong enough jacket to withstand whatever physical things you do to it.

The various versions of the USB spec call for magic limits on length, capacitance and other parameters. Most likely any short extension you add will not effect the operation.

----- Ignore the following unless you like boring details

Electrical engineering rational behind the previous advice- the usb is designed for a maximum cable delay of 1500ns. Signals require just under 2ns per foot (1.8 is the text book value) to travel down the wires. So that allows a physical limit of just over 700 feet. Capacitance effects will come into play before that. And transmission line effects wont happen until approximately 1/10 of that which is around 70 feet. The specifications prohibit cables longer than 16 feet, which is designed to be sure that no-matter-what it will work. WIth a little care it can probably be made to work at distances well over 100 feet.

The cable has resistance, so the power capacity of USB will degrade with distance. That is directly computable from the wire gage you use and the amount of current needed. The shopbot has its own power, so I suspect there is none being carried on the power line of the USB, so it should not be a factor.

The twisted pair for the data does matter, though it is not super critical. I have worked with LVDS signals in other applications where they were not twisted for "equipment cabinet distances" and everything still worked ok. The length of the + and - should be very close to the same, and twisted cable helps there.

----

Feel free to add some wire if you need to, or replace the original. There is nothing really magical about it. Try it, save the original cable, you can always go back.

D

[ken_rychlik]

72% should be ok. Not great, but ok.

I had issues with the oem usb cable and bought one from radio shack. It was about 35 dollars and works fine. Mine is a serial to usb convertor cable. Depending on your vintage of machine, yours could be a different type of cable.

How about the ram on the pc?

[ATX Poly Products]

Thanks for all the info everybody...

The cable in my control box is a type USB B end by the way. I replaced the oem cable with a RadioShack gigaware gold plated cable. The cable seems like a good quailty. I also am giving a differant hub a try from there.

Speed test now says 82%. I don't think it can get much better than that.

The Ram of my laptop is well above the req. shopbot needs also.

I have narrowed the comm lost down to maybe grounding. I have a solid electrical ground going back to my breaker box. Maybe I should also have a separate ground to a rod just for the bot?

[ken_rychlik]

Adam, two things are bad about grounding.

Dust colection, and spindle wiring.

Make sure you have those covered well.

I didn't do a ground rod, but I did run quite a few grounds. Even grounding the pc case to the controller ground at the board.

In the 80's for the comm test is very good.

[ATX Poly Products]

Thanks Kenneth,

I have solid soldered grounds on my dust collection and I am running a PC router head that is grounded through the power cord and the frame of the bot off the case screw.

I did a separate ground rod to the frame also... I still have the same problem going on...

Another thing that is strange. These are the steps I take to powering up all of my system in this order...

Turn on Computer and let it boot up
Turn on the bot control box
open Shopbot 3
Out come is no comm found

then I close Shopbot 3
unplug USB cable and plug in
Open SB3 and it locates the tool just fine...

[ken_rychlik]

I think you should put away the laptop and go in the closet to find a used desktop. If you don't have one, a friend probably does.

I was talking about grounding the pc case to the controller, but that only applies to desktops.

I just re-read all the post and realized what you were doing.

[donchandler]

Thanks Kenneth,

I have solid soldered grounds on my dust collection and I am running a PC router head that is grounded through the power cord and the frame of the bot off the case screw.

I did a separate ground rod to the frame also... I still have the same problem going on...

Another thing that is strange. These are the steps I take to powering up all of my system in this order...

Turn on Computer and let it boot up
Turn on the bot control box
open Shopbot 3
Out come is no comm found

then I close Shopbot 3
unplug USB cable and plug in
Open SB3 and it locates the tool just fine...

I had the same problem with having to unplug and replug the USB cable on my PRT Alpha. Drove me nuts.
I went into windows and turned off all the stuff that was running in the background. Seemed to fix it. Haven't had the problem in quite a while now.

[ken_rychlik]

Don

Good point about the background stuff.

Anti virus, auto updates, screen savers, laptop plugged in to power, ect..

That would cause kicking out mid file, but I don't think it would affect boot up connections though.

There was a mach page that had suggestions about how to turn off all the fluff that would hurt operation of a machine, but I can't find it right now.

Anyone got the link?