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  #1  
Old Wed 21 May 2008, 05:15
dmoore
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USB Ports on the Y-Car - no really...

I'm getting to the final stages of my MechMate build and I'm wiring for proxies, z-touch plate and e-stop. It occured to me (and others I suspect...) that putting USB ports into the y-car might not be a bad idea. Here's why -
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  #2  
Old Thu 22 May 2008, 15:25
WTI
Just call me: James
 
Detroit (Michigan)
United States of America
An interesting argument.

Is there a heavy duty cable that can withstand the constant movement?

The USB 2.0 limit for length is 16 feet (5 meters), so that is a consideration too.
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  #3  
Old Thu 22 May 2008, 16:06
Alan_c
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Grabouw (Western Cape)
South Africa
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Quote:
Originally Posted by dmoore View Post
[*]I find the Shuttle invaluable (see http://www.mechmate.com/forums/showthread.php?t=383) and what better than to just have the Shuttle stay on the y-car where I use it anyway
Keep in mind the size of this machine, having the shuttle on the Y-car will put it out of reach for much of the working time, better to have it in your hand or in a cradle near the 0,0 corner. The idea of climbing onto a moving machine to catch the y-car to reach the shuttle sounds dangerous
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  #4  
Old Thu 22 May 2008, 17:01
dmoore
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Quote:
Originally Posted by WTI View Post
Is there a heavy duty cable that can withstand the constant movement?
I've got double shielded 4 conductor cables I used for my steppers and e-stop that are designed for constant flex - so that should be ok. Here are some spec I found:

USB signals are transmitted on a twisted pair data cable with 90Ω 15% impedance,[6] labeled D+ and D−. These collectively use half-duplex differential signaling to combat the effects of electromagnetic noise on longer lines. D+ and D− usually operate together; they are not separate simplex connections. Transmitted signal levels are 0.00.3 volts for low and 2.83.6 volts for high in Full Speed and Low Speed modes, and 400mV in High Speed (HS) mode. In FS mode the cable wires are not terminated, but the HS mode has termination of 45Ω to ground, or 90Ω differential to match the data cable impedance.



Quote:
Originally Posted by WTI View Post
The USB 2.0 limit for length is 16 feet (5 meters), so that is a consideration too.
I'm planning on putting a "junction box" on the X axis at the end-point for the cable chain. In this box I am putting a powered USB hub, so I should be able to get the needed distance. Here is some additional information:

Maximum Useful Signalling Distance
Although a single cable is limited to 5 meters, the USB specification permits up to five USB hubs in a long chain of cables and hubs. Consequently the maximum possible signalling distance is 30 meters, using six 5-meter cables and five hubs. In actual use, the last hub is a more convenient endpoint since some USB devices include built-in cables intended to directly connect to a hub, setting the maximum useful signalling distance at 25 meters.

Because USB is able to provide power for additional devices connected to the bus, a special type of USB extender cable was created which consists of a miniature one-port USB hub molded into one end of a 5 meter cable. These mini-hubs are fully self-contained within the cable, requiring no separate bulky hub device, and are as simple to use as plugging cables together, with each hub drawing power through all the previous single-port hubs in the chain.
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  #5  
Old Thu 22 May 2008, 17:03
dmoore
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Quote:
Originally Posted by Alan_c View Post
Keep in mind the size of this machine, having the shuttle on the Y-car will put it out of reach for much of the working time, better to have it in your hand or in a cradle near the 0,0 corner. The idea of climbing onto a moving machine to catch the y-car to reach the shuttle sounds dangerous
Good point. Maybe it's better to just hook up the Shuttle to the junction point/hub in the control box mounted on the Mechmate? Then make a holder on the main beam to slide it in or mount magnets to the back of the shuttle?
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  #6  
Old Sat 24 May 2008, 10:24
dmoore
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USB extension for USB in y-Car

Here is an extension that uses standard ethernet cable to extend the USB up to 150ft. The only downside is it is at USB 1.1, not 2.x

http://www.dealextreme.com/details.dx/sku.6640

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  #7  
Old Sat 24 May 2008, 12:45
Marc Shlaes
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Cleveland, OH
United States of America
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Here is a link for a USB2 RJ45 Adapter.

http://www.directron.com/usbrjxt.html

David, I like your "outside the box" thinking. The idea of a web cam cruising around on my Y car pointed at the bit is actually a bit interesting to me. Even with no "practical" use - which I'm sure I could think of a few - it sure would be cool.
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  #8  
Old Sat 24 May 2008, 16:54
dmoore
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Quote:
Originally Posted by Marc Shlaes View Post
Here is a link for a USB2 RJ45 Adapter.

http://www.directron.com/usbrjxt.html
That appears to be the /same/ thing... While DealExtreme is cheap (they ship directly from China), it does take about 2-3 weeks to get your stuff.

Quote:
Originally Posted by Marc Shlaes View Post
The idea of a web cam cruising around on my Y car pointed at the bit is actually a bit interesting to me. Even with no "practical" use - which I'm sure I could think of a few - it sure would be cool.
Cameras on the Y-Car seems silly but it has real-world, practical applications:

Accurate video-based center finding built into Mach3: http://www.machsupport.com/forum/ind...ic,2519.0.html

The ability to safely watch the progress of a job without sticking your head and hands near the router. It should also allow a closer view than you could get hovering over the table looking at a bit spinning at 20,000 RPM. This is even more useful for people that have their CNC machine running in an isolated room. For people with staff handling machines, it might be useful for monitoring.
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