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View Full Version : PRS ALPHA, firewire to serial?



dray
08-21-2007, 11:55 PM
Has anyone tried anything besides USB?

On occasion when I am cutting rapidly I get chatter (actually a heavy KLUNK KLUNK) from steppers not giving and getting info from my PC fast enough.

I have about 20' of USB cable with a powered USB hub in the middle. I would like to get rid of the chatter, I wonder if anyone has tried firewire to serial to interface with the control board?

Thx!

fleinbach
08-22-2007, 06:54 AM
Danny,

Have you tried a speed test of your USB port.
If not just type in UT and there you will find some testing tools. One is a speed test and there is also a set of instructions. It says you should have at least a 70 to function properly. I ran an older 800MZ HP for 4 years with few problems and upon testing was getting between 69.8 and 70.6. I just switched to a 1.3 GH and now I get an average of around 89.2

Also is your computer dedicated to the Shopbot. From your description "I have about 20' of USB cable with a powered USB hub in the middle" it doesn't sound like it is.

harryball
08-22-2007, 09:12 AM
Drop the hub and dedicate the PC to run the bot. Run the diags, I'm at 75% and have no problems running at 12 ips and jogging at 22 ips. I do, however, eject the network card when I run. I've found if it gets polled while running above 8 ips I get the same klunk klunk you are talking about occasionally.

Robert

henrik_o
08-22-2007, 12:29 PM
I don't know the scaling involved between command instructions -> machine instructions, but I'd have to seriously question whether it could saturate even USB 1.0, much less 1.1. If there's saturation, it's likely on the serial bus itself though an industrial implimentation like in the Shopbot ctrlbox should have no problems.

I dunno, but this sounds more like a bad signal. I guess it could be physical (cable too long, loose connectors etc), radiative (electrical noise/ radio interference) or systemic (OS interfering with COM port, etc).

I'd probably check an extra time that the physical setup is nice and tight, not too long, not too close to sources of interference, and then check that there's no background shenanigans going on with the computer driving the bot.

blaz_in_az
08-24-2007, 12:22 PM
Danny,
I had problems with losing the, control box to computer, connection and I also had a problem needing more length than the 10' cable supplied by ShopBot. I needed about 13'. I had added another 3' usb cable and it worked for a while.

On my PRT alpha, ShopBot uses a short cable, inside the cabinet, to convert from serial to usb, and then they give you a 10' usb cable. By adding another 3' cable, most likely caused my problems by having three junctions in my "direct" cable.

I found out that the recommended "maximum" length for a usb cable is 16'. I purchased a 16' usb cable with a repeater on the end and replaced my 10' and 3' cable. This resolved the problem by getting rid of the extra junctions and having a repeater for the distance beyond 16'.

You mentioned a 20' cable with a repeater in the middle. If the longest cable is less than 16', your alright, but maybe too many junctions?

I hope this is of help.