[buz0340]

Hello,

I have recently developed a new problem where my stepper motor will reverse for no reason while executing my G code. I am running EMC and the screen shows that the motors are operating correctly, but really the motors are not. This is happening on only one axis.

What could create this type of problem?

Any help is greatly appreciated.

Thank you,

Brian

[Al_The_Man]

Possibly intermittently loosing your Dir pulse on that axis?
Al.

[buz0340]

Hey Al,

Yeah, I was kind of thinking the same thing. Does the dir signal high for one direction and low for the other or does it accept a sequence? It appears that the wires are secure. I'll double check my parallel port cable, I hope its not a faulty board.

Thank you,

Brian

[TOTALLYRC]

Hey Al,

Yeah, I was kind of thinking the same thing. Does the dir signal high for one direction and low for the other or does it accept a sequence? It appears that the wires are secure. I'll double check my parallel port cable, I hope its not a faulty board.

Thank you,

Brian

Hi one way and low the other.

[buz0340]

Hello again,

I checked the wires and they are all hooked up properly. I checked the signal, and it coincides with the direction indicated in the G code. So no problem there. I can almost make the motor change directions on command by pressing the axis in that direction. If i put resistance on the router, it will reverse the direction. And I can do the same thing to make it go back the other way.

What are the chances something is wrong with my board (L297/298)?

What else could I test?

Thank you,

Brian

[mactec54]

Ho buz0340

Are you using sheilded cables

[buz0340]

My parallel cable is "shielded" but all of my jumper cables from board to board in addition to my motor cables are not shielded.

If this is the problem, would the shielded cables be preventing outside environment interferences or other interferences produced from signals on the board?

Is there a simple way of testing this theory, or do I just have to replace the cables and give it a try.

Thank you for your input.

[mactec54]

Hi buz0340

The most interference will come from the spindle motor then your steppers does it do this with the spindle running or just with the steppers moving/engaged

If you do put shielded wires on your motors make sure you only ground the input end of the shield

You really want to use shielded wires were ever you can

[buz0340]

Hi again,

This happens when the spindle is not running. I also isolated the board with the problem by disconnecting the power to the other two as well as the step/dir signals. I still had the problem. I am beginning to believe shielded cables will not help. If you have any other comments I would love to hear them.

thanks

brian

[JonLed]

Try swapping the x and y drivers and see if the problem follows the drive.

Jon

[buz0340]

I have tried that previously. Its the same board that has the problem.

Thanks for the input jon

[JonLed]

I had something like that happen to me before. Although my drives don't use the L297/298 combination, if I recall they still use sensing resistors. Anyway turned out that one of the sensing resistors was not soldered and only making intermittent connection. I would suspect that half of the drive output is weak for some reason. Do you have a scope?

Jon

[buz0340]

No scope, just a multimeter.

[JonLed]

Is it a commercial drive or something you built? Got a schematic?

Jon

[buz0340]

Hey Jon,

Here is the schematic.

http://picasaweb.google.com/lh/photo...eat=directlink



Thanks for your help Jon

[JonLed]

Not sure how much I'll be able to help, but I guess the first thing I would do is compare the voltage readings at pins 1 and 15 of the 298 while it's running, they should be close to the same. Then I would check the voltages at pins 2,3,13 and 14, again, these should be close to the same.

Jon

[buz0340]

Do I check the voltage when the motors are stopped or do they need to be jogging.

Were you able to see the schematic?

Thanks Brian

[JonLed]

Check the voltages while the motor is moving at a constant speed.

I could see the schematic and took a look at the rest of your machine. Has this been running before with no problems?

Jon

[buz0340]

Hey Jon,

I have not had all 3 axis running at the same time yet. I have 2 axis running consistantly without problems. I didnt catch your reply in time and tested it while at rest. I will next try while its moving at constant speed. Anyways here is what I got

Current Sensing B: 2.5V
Current Sending A: 1.0V
Output 1: 9V
Output 2: ~0.1V
Output 3: ~0.1z
Output 4: 11V

Brian

[buz0340]

Here are the new results: the form is (voltage @ const. speed)/(voltage @ rest)

Current Sensing B: 1.84V/2.65V
Current Sending A: 0.39V/1.09V
Output 1: 5.7V/9.13V
Output 2: 1.6V/4.45V
Output 3: 0.3V/0.45V
Output 4: 8V/11V

Hopefully something will make sense.

Thank you,

Brian