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Author Topic: Motors driving willy nilly  (Read 9876 times)

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Offline Leeway

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Motors driving willy nilly
« on: May 05, 2007, 07:39:47 PM »
Hey guys.
Thought I would ask this here too. Perhaps someone has an idea that may help.
I am having a lot more trouble with my second build, which is a plasma cutter.
First was a router with a 3 axis Xylotex. I didn't even need a BOB for that one.
I am using Gecko 201's. I had initially setup to use a standard no frills BOB, but just swapped out to a Mini I/O2 board. I had been running the 5 volts from my lab supply, but this mini has it onboard.
I have my step and dir hooked up correctly I think. I have the estop working. All motors are working as well. The Z axis seems pretty stable, but X and Y are intermittent when jogging in either direction. Both directions will go both ways.
I am running shielded cables and they are grounded at the drive cabinet. They run all the way to the motors, but are not connected.
My motors aren't connected to anything. Not even grounded. Just sitting on the floor. I wonder if grounding them would help now that I think about it.
Anyhow.
I am getting the proper voltages at all locations. This mini I/O has the little led card that shows step and dir for the axes when running. The step leds work as they should I think, but the dir leds only come on sometimes when I jog one direction, not the other. That is to say using one key and not the other. The motors still go both ways. Also the A axis isn't even connected and those led's work at times as well.

Now I have the 5 volts connected to the gecko's 5v common. The PC ground terminals on the board are not connected, because I don't know where it would go. Instructions are kinda odd on that. It says PCGND is common for all drives. The 5V terminal says +5 for common to all drives. I realize that the +5 common is labeled that way on the Gecko's, so that was easy. The ground is confusing. I'm pretty sure it should not go to my high voltage ground. That is separate.
Sooooo.......any ideas on what the heck is going on?  ;)

Here are a couple of photo's so you should be able to see the wiring maybe.
Thanks.

http://leestyron.com/cnc/cb2.jpg

http://leestyron.com/cnc/cb3.jpg
Lee

Hood

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Re: Motors driving willy nilly
« Reply #1 on: May 06, 2007, 06:32:46 AM »
The LED for Dir should be on one way and off when you jog the other, is this what you get?
 I am not too clear on what you mean when you say "Both directions will go both ways." are you meaning if you jog using the left button it may go left then next time right?
Hood

Oh BTW think probably the PC ground will just be the ground from your Parallel port but not 100% sure

Offline Leeway

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Re: Motors driving willy nilly
« Reply #2 on: May 06, 2007, 06:54:26 AM »
Okay.
Sounds like the red LED is working like it should then.
You are correct about the X and Y driving either direction with one arrow key, then the same when I try the other arrow key.
I have tuned the motors from about 40 Vel and 5 acc to 500 vel and 45 acc and the results were the same. They run pretty good, but errantly.
I have tried the different pulse ranges from 0 to 5 on all axis as well and that didn't effect the stable Z drive. I have not swapped the motors yet with this board, but I will try that.
I have tried the motor drive step and dir active low and they work best on active high.
I have another new cable that will run my THC 300 and second PPort and I can swap that out. I will check it also for straight pass though on the wiring.
I am running this one at a freq of 45000 and its pretty stable. I will try these things, but I am slowly running out of safe ideas to check.  ;)

I wonder if I should try to hook the drives up to PPort 2. That may give me another thing to test or eliminate.
Thanks Hood.
Lee

Hood

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Re: Motors driving willy nilly
« Reply #3 on: May 06, 2007, 07:02:35 AM »
Sounds like swapping out hardware will be the best move, try swapping the Z drive for the other axis drives and see if the problem moves around.
You will get there in the end and it will likely be something simple, most of us have been there ;)

Offline Leeway

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Re: Motors driving willy nilly
« Reply #4 on: May 06, 2007, 10:18:37 AM »
Thanks Hood.
I did swap some stuff out.
I swapped out computers to this laptop.
I removed the charge pump plug in and jumpered the board on pin 1 and 2 like the manual states.
I disconnected the led's.
I swapped out the motors.
All three run well on Z.
I swapped out the wiring between the drives and the BOB.
Tried motor tuning with the different setups.
Swapped out Pport cables.
Checked the cables.
They are straight pass through.
The only thing I have left to do that I can think of is to swap the gecko's.
I will remove the Z gecko and place the Y one where the Z was.
If it runs good there, then there has to be some noise somewhere.
If not, then the two drives will need work.
All three power led's in the gecko's work and stay on.
When I drive the axis, the led's flash dimly.
Not having used gecko's before, I assume that is a normal condition, especially since the stable drive does the same.

I remeber checking the jumper settings in the gecko's, but will double check those.
Next post will be my results of swapping out the drives.
Lee

Offline Leeway

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Re: Motors driving willy nilly
« Reply #5 on: May 06, 2007, 10:48:10 AM »
Okay.
I moved the errant Y gecko into the spot where the stable Z gecko was. It now works as it should, so apparently, the drives are okay.
Thats good.
I guess its a noise thing.
If you look at my first picture, you can see that the motor wires are above the two offending axes, but not over the third. They are somewhat offset. They are not shielded right there either. Only to where they enter the cabinet.
Could this be the trouble spot?

The shield grounds are also above these drives.
Lee

Hood

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Re: Motors driving willy nilly
« Reply #6 on: May 06, 2007, 02:04:52 PM »
Could well be, I have shielded cables on everything in my mill, only wires that are not shielded are the power wires into the geckos.
Hood

Offline Leeway

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Re: Motors driving willy nilly
« Reply #7 on: May 06, 2007, 05:53:43 PM »
Do you think an aluminum plate slid in between the drives and the incoming wires would help prevent any noise? What about lead or brass? I have sheets of all three. I would really hate to start all over again on the cabinet. The reason there are no shields in the cabinet is because I used pigtails so I would have plugs and receptacles at the case.

Now if I take it a step further. Can I wrap a ground wire around each drive wire bundle and expect that to help?
I'm not an electrician or electronics guru. I did take basic electrical classes and was a Generator mechanic in the Army, but that was long ago. I do understand the priciples of basic stuff, but I usually deal with noise by changing the channel or turning down the volume.  ;D
I don't recall installing a noise reducing knob either, so I am boxing shadows now. Thanks for any suggestions on grounding or reducing noise problems.

Lee

Hood

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Re: Motors driving willy nilly
« Reply #8 on: May 06, 2007, 05:57:42 PM »
I think you can buy sleeving to shield your wires,  its kind of like a braided cover. Might be worth looking into that. Dont think the Alu or lead plates will help but as I know  less about electronics/electrics than you I would take that with a pinch of salt.
Hood

Offline Leeway

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Re: Motors driving willy nilly
« Reply #9 on: May 06, 2007, 06:21:06 PM »
I found some that I will try out. It's part number 5537K27 at Mcmaster Carr. Page number 773. $1.41 per foot.
Here is the description.

Braided Tinned Copper Mesh Sleeving
   Flexible yet sturdy, this braided sleeving protects wire, cable, and hose in highly abrasive environments. Just cut with scissors; sleeving expands for installation and can be pulled tight around the bundle for a secure fit. Designed for EMI shielding and grounding applications. Color is silver. Maximum temperature is 257°  F. Maximum continuous length is 1000 ft.


I think if anything will do it, this will.
Maybe I won't have to rebuild the whole thing. Thanks, Hood.
Lee