Machsupport Forum

Mach Discussion => General Mach Discussion => Topic started by: obhitn3 on March 13, 2009, 09:10:34 AM

Title: Motor "Sometimes" goes in Wrong Direction while Tuning
Post by: obhitn3 on March 13, 2009, 09:10:34 AM
Made some serious headway tuning the motors last night. NOW the direction is possessed and none of the 3 ways in the MACH3 Manual seem to fix it. While tuning, the UP ARROW Key should make the motors turn + and the DOWN ARROW Key should move the Motors -.

This is the case only 50% of the time. It is unreliable at best

A sample would be like below:

UP ARROW - Moves the motor +

DOWN ARROW - Moves the Motor -

UP ARROW - Moves the Motor +

DOWN ARROW - CONTINUES TO MOVE THE MOTOR +

They sometimes move in the direction they should, however after 3-4 movements in the correct direction, the motors WILL ALWAYS move in the WRONG direction when the opposite ARROW is prressed.

Any ideas?
Title: Re: Motor "Sometimes" goes in Wrong Direction while Tuning
Post by: Hood on March 13, 2009, 09:24:37 AM
Sounds like for some reason your direction signal is not getting through. Check the wiring and if that seems fine then maybe change the active state to the opposite of what you have at the moment.
Hood
Title: Re: Motor "Sometimes" goes in Wrong Direction while Tuning
Post by: Waynec on March 13, 2009, 04:16:06 PM
I recently resolved a similar problem with my CNC.  I have two motors on my Z axis, and one would quit turning one direction, so that even when I changed directions, one motor would obey, and the other would not.  The result was an instantly racked gantry.  

The problem is slightly different, in that the motor in question is NOT turning in one direction.  In your case its turning in the WRONG direction.  Be sure that is the case.  In my case I had to disengage the motor from its rack gear to clearly see the direction of the pinon gear.  

In my case a motor winding was not getting voltage, which ended up being a bad connection at the Gecko driver for that motor.  When I pushed on the connector I got the motor to work correctly, but only intemittently. I replaced the Gecko and installed new connectors and its been working fine.

But I have to add that I probably BLEW the Gecko by prodding around at the connector when I was troubleshooting.  It sparked once, and then quit working altogether.   I guess that made the repair easier, but more expensive.  

If you are using Geckos, try swapping out both the Gecko and the connectors.  I now keep a spare Gecko driver so I can do this.  

Good luck, and don't get too frustrated.  It'll fix.  

Wayne from White Salmon

Title: Re: Motor "Sometimes" goes in Wrong Direction while Tuning
Post by: MAKESOMECHIPS on March 17, 2009, 11:44:41 AM
I have tried the above fixes and no dice this is happening on all 3 axis's the drives were just returned from gecko with a clean bill of health any more thoughts

thanks

Jamie
Title: Re: Motor "Sometimes" goes in Wrong Direction while Tuning
Post by: Tweakie.CNC on March 17, 2009, 12:36:15 PM
It could be that the direction signals are somehow getting corrupted. You are not using and active BOB (with opto isolators) prior to your Gecko connection are you ?.

Tweakie.
Title: Re: Motor "Sometimes" goes in Wrong Direction while Tuning
Post by: MAKESOMECHIPS on March 17, 2009, 02:03:24 PM
i do not know what an active bob is so probably not unless it is built into the software and can be checked as a box

i can take some pics if it would help

thanks for your time

jamie
Title: Re: Motor "Sometimes" goes in Wrong Direction while Tuning
Post by: Tweakie.CNC on March 18, 2009, 03:33:08 AM
Hi Jamie,

Sorry I just assumed you would know.
A breakout board (BOB) is where the LPT connection from the computer joins with the machine. Some BOB's are 'active' in so far as they incorporate opto isolators and are powered 5 Volts. The Gecko controller already incorporates opto isolators on its inputs and sometimes behaves oddly if active BOB's are used. For Gecko operation a passive BOB is usually used.
Hope this explains what I was getting at and once again sorry for posting a reply that was not fully explained.

Tweakie.
Title: Re: Motor "Sometimes" goes in Wrong Direction while Tuning
Post by: MAKESOMECHIPS on March 18, 2009, 07:23:09 AM
Tweakie I appreciate your time and thoughts the BOB I have doesn't seem to be active it looks like a plain circuit board with no electronics on it at all.

any other ideas

thanks

Jamie
Title: Re: Motor "Sometimes" goes in Wrong Direction while Tuning
Post by: Tweakie.CNC on March 18, 2009, 07:34:54 AM
Hi Jamie,

As Hood said earlier have you tried changing the direction signals from active high to active low (or visa versa) ?. This is under Configuration, Ports & Pins, Motor Outputs.

Tweakie.
Title: Re: Motor "Sometimes" goes in Wrong Direction while Tuning
Post by: MAKESOMECHIPS on March 18, 2009, 08:04:53 AM
yes i have tried that with low settings on acceleration and velocity that seems to give the motors the power to get going without it they don't even turn at all

but with higher settings on accelleration and velocity it doesn't seem to make any difference

thanks

Jamie
Title: Re: Motor "Sometimes" goes in Wrong Direction while Tuning
Post by: Tweakie.CNC on March 18, 2009, 01:30:20 PM
Hi Jamie,

No other suggestions, sorry.

Incidentally do the motors have sufficient torque ?. (can you stop them with little force when they are rotating).

Tweakie.
Title: Re: Motor "Sometimes" goes in Wrong Direction while Tuning
Post by: MAKESOMECHIPS on March 18, 2009, 01:48:44 PM
no they seem pretty powerful and when i turn up the velocity and accelleration they take off fast and smoothly and go rapidly
it is just very frustrating to see them go the right way 3-4 times then the 5th time go the wrong way.

Thanks again for putting your mind towards my problem.
Title: Re: Motor "Sometimes" goes in Wrong Direction while Tuning
Post by: Hood on March 18, 2009, 03:10:00 PM
Put a Voltmeter between the 0V and Dir pin on your BOB and jog back and forth to see if it goes 5v to 0V when you jog one way and 0v to 5V when you jog the other. It may well be that you only have 3.3v from your port which will be your problem as they are often not good enough to drive the drivers. To solve that problem you could get a BOB which is powered, most of them can accept the lower 3.3v signals and will output 5v. The ones I like are the PMDX 122.
Hood
Title: Re: Motor "Sometimes" goes in Wrong Direction while Tuning
Post by: MAKESOMECHIPS on March 18, 2009, 03:45:33 PM
when you say 0 volt you are saying put one contact on the ground and the other on the direction pin at the break out board or on the driver? to check this?

ok the 5 volts that it should be getting is from the computers power supply on my system.  is that adequate? I guess i will find out for sure when I get home tonight to check

thank you all for your your time and input

Jamie
Title: Re: Motor "Sometimes" goes in Wrong Direction while Tuning
Post by: Hood on March 18, 2009, 04:05:24 PM
Yes thats correct, its commonly called Gnd but really its 0V, doesnt matter whether its the BOB or the Drive as they are one in the same with a non powered BOB, so whichever gives you easiest access.
The 5v it is getting is from the parallel port which ultimitely is coming from your computers PSU and yes it will be adequate, however modern design of parallel ports often has them powered by 3.3v rather than 5v which causes problems with the drives not picking signals up properly on occasions. Using a powered BOB will eleviate this problem as the BOB will be happy with the 3.3v signals from the port but it will put out 5V so that the drives are happy. As was mentioned optically isolated BOBs are not always a good thing when it comes to drives that have optos already in them, so best to make sure any powered BOB you may get doesnt have optically isolated outputs for Step/Dir pins.

Hood
Title: Re: Motor "Sometimes" goes in Wrong Direction while Tuning
Post by: MAKESOMECHIPS on March 18, 2009, 10:46:54 PM
Hood you were correct i am only getting 3.3 volts to the BOB on pins 1-9 and when i change directions it drops to .51 volts

but on pins 11-15 I am getting 5 volts but the voltage does not drop at all no matter what direction i move the table.  so I moved my direction wires to pins 10 and 11 just to try it and it still goes whatever direction it pleases.

So do you still feel i need a different breakout board?

Thanks again for your time

Jamie
Title: Re: Motor "Sometimes" goes in Wrong Direction while Tuning
Post by: Hood on March 19, 2009, 03:55:22 AM
Port 1,  Pins 10 to 13 and  15 are Inputs so you cant put motors on them.
 Cant say for definite that it will cure your problem but certainly would suspect it will. A cheaper option for you may be to get a PCI parallel port and use that as they tend to be 5v, but again some are some are not.
Hood
Title: Re: Motor "Sometimes" goes in Wrong Direction while Tuning
Post by: MAKESOMECHIPS on March 20, 2009, 09:30:04 AM
i purchased a powered pci card so after getting my spiffy new thing and installing it

it proceeded to do the same thing it had been doing 3/5 or 4/5 it would do what i asked it to then it would do whatever it wanted to do.

after much head scratching I thought despite what I had been reassured I really think my motors are wired wrong.  So i got out my multimeter and sure enough they were out of phase for their continuity.  So i rewired them to be in phase and voila they work perfect.

thank you all for taking the time to help me

Jamie
Title: Re: Motor "Sometimes" goes in Wrong Direction while Tuning
Post by: Hood on March 20, 2009, 10:01:31 AM
Thats great news :)

Hood
Title: Re: Motor "Sometimes" goes in Wrong Direction while Tuning
Post by: MAKESOMECHIPS on March 20, 2009, 10:03:59 AM
I thougth so and i even made some cool circles in styrofoam and some rectangular pockets as well.  My wife wasn't nearly as impressed as I was with my projects ;-)
Title: Re: Motor "Sometimes" goes in Wrong Direction while Tuning
Post by: Hood on March 20, 2009, 10:05:27 AM
Its often the case ;D

Hood
Title: Re: Motor "Sometimes" goes in Wrong Direction while Tuning
Post by: MAKESOMECHIPS on March 20, 2009, 10:08:08 AM
Thanks again Hood you were most helpful

do you happen to know of any wizards included in the mach software that will help me turn an inside and outside cone shape on barstock?
Title: Re: Motor "Sometimes" goes in Wrong Direction while Tuning
Post by: Hood on March 20, 2009, 10:13:24 AM
Is it a Lathe? as the lathe wizards have that.
 If its a mill then its not going to be easy to get a good finish unless you can chuck the stock in a collet holder, If you can then you could  use a Turn profile with a lathe tool clamped to the table or in a vice.
Hood
Title: Re: Motor "Sometimes" goes in Wrong Direction while Tuning
Post by: MAKESOMECHIPS on March 20, 2009, 10:18:58 AM
It is this machine on the home page of the link below it is both a lathe and a mill

http://www.shoptask.com/

I will have to look at the lathe wizards

thank you very much