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-   -   usb to db25 parallel cable (http://www.mechmate.com/forums/showthread.php?t=464)

smreish Mon 08 October 2007 20:14

usb to db25 parallel cable
 
Forum.
...as I ponder going back to the "old school" for my controller due to the less than "bullet proof" G100, I found a USB to Parallel cable so I can use my laptop on the go.

Tiger Direct.com $12.95 Completely IEEE bidirectional.

Just thought I would pass on the good find.
Sean

http://www.tigerdirect.com/applicati...1274&CatId=471

Marc Shlaes Tue 09 October 2007 04:44

Is the typical "lack of parallel port" the only reason that a laptop is not recommended? I recall reading something, somewhere, about using laptops for machine control but I can't remember exactly what it was or where I read it.

Hugo Carradini Tue 09 October 2007 08:52

Marc, I think they don't give the 5 volt you need. They give up a lower voltage.

smreish Tue 09 October 2007 10:03

Yep....3.3 VOLTS. But, if you use a small 20 dollar USB self powered hub between the two, you can get 5 volts regulated off the output of the hub device.

Question 1 :Does the Mach software support USB to Parallel emulation? Or do I really need a bonified Parallel card to make it work.
Question 2: Can I use a USB port, with a hub so I have 2 USB to Parallel cables to drive 2 PMDX-122 boards so I can run 5 axis motors. 2x, 1y, 1z and 1 indexer?

driller Tue 09 October 2007 10:36

The spec for the parallel port is 3.5 volts at 3.5ma.
most desktops deliver 5 volts and more current.

Any decently designed breakout board will work with the 3v signals.

Check the Gecko. if it cannot, then you can add a transistor to get the 5 volt power.

The other reason laptops are not so highly recommended is that the newer ones do not have any parallel ports.

Dave

Bill McGuire Tue 09 October 2007 10:37

Just a thought..
Emulation software slows down instruction processing. This diminished speed may affect the way instructions are handed to the motors...

smreish Tue 09 October 2007 11:23

Bill....my concern as well.
The really big question I have is...can I daisy chain pmdx-122 together to get 5 or 6 axis of control? I have a call into Steve at PMDX for an answer...just waiting.

Thanks for the feedback.
Sean

stefanv Tue 09 October 2007 21:04

Sean,

Consider the option of hooking 2 Geckos (2x) to one out signal from your BOB. By reversing one of the leads to the motors from the second Gecko, both will move in opposite directions at the same steps, just like mirroring them in Mach3. This will free up a channel on your BOB for the indexer. Ask Steve at PMDX if this is possible with his board. It is for me with the Bob Campbell board using 2 G202s.

Good luck
Stefan

smreish Wed 10 October 2007 06:55

Stefan,
Mr. Stallings at PMDX did confirm that I can do as you suggest and steal the steps to drive two motors. It will work - most likely without fault - for years. The only concern is that Mach can only "see" the single axis...I want the CNC logic controller to see Both motors with respect to position and faults. So, for the minor cost of an additional board and a parallel port card...all of which will be around 100 dollars, I am going with the later setup for safety and expandability. The big plus is I get extra I/0 if I add the second board! :)

Thanks for everyone's input. I am off to buy parts now.

Sean

Gerald D Wed 10 October 2007 07:58

Mach cannot see any "position and faults" other than a limit switch - not sure what is being said here?

smreish Wed 10 October 2007 09:11

Gerald.
You are absolutely correct. Now, I have confused myself. I have been dealing with Servo's and encoders so much lately that I forgot I am using Steppers. No memory little motor's no more sophisticated than the starter on my car. Ugh...sorry for the threads of confusion. Done. 1 board, 5 geckos, parallel porting the x axis.

Yep...sometimes the cloud over my keyboard keeps me from seeing the light.

Sean

Gerald D Wed 10 October 2007 09:26

The big lesson I learnt through all of this project is that this CNC monster is much simpler and stupider than what it is hyped up to be.


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