3 axis setup: 2 motors work fine, 1 locks up

[chozo]

What would cause a motor to studder or lock up when being ran?
Keep in mind they are not connected to anything (except the wires of course).

I have a 3 axis board from HobbyCNC, with 3 motors hooked up.

I'm using Mach 2.

I was jogging them around to test everything out, and I noticed X works fine, Z works fine, but Y locks up half the time. I might press "+" and it works, then press it again, and it just vibrates.

What can cause this?

Thanks a million!

[Alex S.A]

I think something is locking the motor up. Is Always this happening at the same place? If so, it is a mechanical problem you can correct it. You also have to check the encoders parameters. You can explain better when you say : it vibrates... coz the motor might have tried correct itself position....

[chozo]

When I jog it forward or backward, it will spin smooth half the time, and just stutter/vibrate the other half. It's just random.

The other two motors spin perfectly fine.
I have the same settings for all motors.

[CNCPlastic]

Check your parallel port with a volt meter. When I first connected mine I was having all sorts of problems, turns out some of the pins I expected to have zero volts had 5vdc. I had to install a cheap aftermarket parallel port card and it worked fine after that.

When I upgraded that pc recently to a better pentium 4 2.26ghz motherboard built by Intel no less, that built in parallel port was even worse, there must have been 4 or 5 of the pins with 4-5vdc that were supposed to be zero. Again I installed an aftermarket parallel card and it works great.

For some reason the manufactures are powering those pins, probably for aftermarket stuff like swappable dvd drives and the like. This issue can be really bad if you are using a notebook. Test every pin you plan to use.

[chozo]

Do I test the voltage at any time, or when I'm actually using it(like testing the two pins for that axis while I'm jogging it)?

Right now(not doing anything), it's reading 3.4v on all of the non-ground pins.

Thanks a bunch!

[buscht]

Swap two motors and if its doing the same thing, then you can rule out a motor problem. Then swap wiring, if its doing the same thing you can rule out a cable problem between the controller and the motor.

[chozo]

Okay, I swapped motors. The problem is in the same axis.

I don't really think I need to swap wiring. I have the wires really short right now, for testing, and I can see there are no problems.

What could it be?

Thanks again.

[CNCPlastic]

Test the pins when you are doing nothing, and no programs running, especially not Mach2. Remove the parallel cable from the PC and test the pins at the PC parallel port. Ideally you want all the input/output pins you plan to use to read zero vdc (low) now none will read 0 exactly, you may get some that read 20, 30 milivolts but thats still considered zero. There is a voltage range, I do not know the exact limits but 0 to 1 vdc will most likely be read by the computer as Low zero volt, no signal. 4 to 5vdc will be read as high, it doesn't have to be 5vdc right on the money. But at 3.4 volt you are out here in the middle of lala land and I don't think thats good.

The other suggestion about swapping motors and cables is also a great idea, eliminate some of the other possible causes.

[chozo]

I just tested it again. Reads 4.2v at the end of the cable.

[chozo]

Sorry, I don't know what I'm doing. I soldered together this controller board, built my power supply, but I don't know about this printer cable...

Is there an easy way to test the printer cable pins? It's annoying trying to hold the probes to touch two at a time.
But you said I should test directly at the computer. My probes won't fit in the pin holes.

Let me get this straight...
You said:
" Ideally you want all the input/output pins you plan to use to read zero vdc (low) now none will read 0 exactly, you may get some that read 20, 30 milivolts but thats still considered zero."

I want to use pins 2-7. I should test them coming OUT from the PC, correct? They should or shouldn't read 0vdc?

It should read 4-5vdc, when?

Thanks for your time.

[chozo]

Okay........x_x

I tested it AGAIN, right at the back of the computer, and it's 3.4vdc.

But I wonder why the other axes work fine.

[chozo]

I just did some reading, and found that 3.3v is normal for parallel ports now.

I guess I should get a card...