Linuxcnc and stepper motor comunication

Hi all, first of all, excuse my poor english.

right to it: i cant manage to make my stepper motor move at all, the 7i76 output energizes/de-energizes the motors just fine apparently (first time seeing a stepper in action) when the motor energizes it makes a *stiffening* noise; probably just normal; and it holds the torque just fine.

checked pins on the 5i25/7i76 with halcmd show pin, and the enable signals work, so i would think the boards are just fine.

the driver has a green led light to show power indication. when i power up the driver this led lights up. it also has a red light, for when current exceeds rated value or voltage lower rated value, the red LED lights.

interenting enough, i can see throgh the driver metal enclosure, a red light from the inside of the driver. a different one than the one specified above. It's on all the time. i dont know what it means thou.

i would be inclined to say that the wiring between the driver and the motor is wrong, but as i have been told, i would still see some kind of step movement, wiggling or something from the motor. instead of just holding torque. btw, the motor makes no sound when holding torque or when sending movement commands to the joint.

if its of help, ill link the manual of the motor and the driver for better reference.

Driver (this one has a slight variation to mine, but its quite similar) : purelogic.ru/files/downloads/doc/Driver/...ko_Purelogic_eng.pdf

motor (find in page: FL86STH80-4208B) to found this specific motor datasheet : lineartec.com.ar/catalogos/19Fulling.pdf

please tell me if im missing any important information about the problem. thank you


Frank

Are you sure you have the wiring between motors, drives, and 7i76 correct?
What have you set the drive timings to?
Specifically these settings for each joint/axis in your ini file:

reply+update:
i could make the motors move, changing the wiring on the driver output, but it may still be wired wrongly on the motor side. as it moves but about 1/8 of the distance it should and in a very stiff manner, i think the schematics on the manuals are wrong, i need to figure which cable is in each phase, anyone knows where to find the info?

i would think the 7i76/driver are doing their job according to what happened. correct me if im wrong, i dont have experience on the subject

todd, i've changed those settings to be:

DIRSETUP = 1000
DIRHOLD = 2500
STEPLEN = 1000
STEPSPACE = 2500

thank you for the quick reply on the topic. appreciate it

Frank

I would double the steplen number and try again

oh boy, you sir, you have special powers. as usual, pcw is here to save the day! haha, its working. beautifully. just one question, how can i tune those 4 numbers to take out the best out of my stepper?

2nd-ing Andy here. There is nothing to tune or adjust there. STEPLEN is the minumum number of nano-seconds the step pulse should last. The driver dictates this, as it can either reliably detect every step pulse or not, there is not any in-between area to exist in and tune for. 2000 means 2 microseconds and combined with 2500 yields 4.5 microseconds minimum between pulses. That gives a maximum pulse rate of 222KHz. Most handle 200 to 250KHz so that's in the ball park. Most drivers I have played with tend to look like this:

STEPLEN 2500
STEPSPACE 2500

5 microseconds for a complete pulse, and a pulse rate of 200KHz. That's usually a fairly safe bet on most drives but generally the drive manufacturer must tell you the exact settings to specify.

Let's say you have 5 turn per inch ball screws and 200 step per rev motors. That's 1000 steps per inch. You setup 8X microstepping on the driver so 8000 pulses per inch now. If you want to move at 4 inches per second (that's pretty fast) you still only need 32KHz to do it. You can see, there is little need to try and push right to the lowest limit on the timing. So you can generally pad the numbers with 500 to 1000 extra without any harm.

thanks guys, you really made it clear to me. now i have a much better understanding of a stepper motor. im finishing my first build right now, and im already thinking of building another machine, is it just me or it kind of gets an addiction this stuff, good thing at least i can make money with them hehe.

andypugh wrote:

No, it's not just you.

Hello, my name is Andy and I am a retrofitoholic....

You also get more ambitious. I spent more on custom-made castings for my Holbrook lathe conversion than I spent on my entire first conversion. (and that includes buying a brand-new Chinese lathe.mill machine)

Andy, I'm sure I remember you saying on one thread that castings were reasonably priced in your neck of the world. I think the truth is coming out....

But your work on that machine was amazing!