Pseudo Power Feed Question

[stevens157]

I have a few of these boards I am using to finish up a lathe cnc conversion. Since I had an extra board I was wondeing if there is a way to maually run a stepper motor so I could use it as a pseudo power feed on my mill until I get around to finishing the rest of my mill conversion. Maybe it is a bad idea but it never hurts to ask. Thanks

Mike

[PMinMO]

Is it possible, yes. Do I have something for it at this time , no. Bascially all that is needed is a small timer circuit like a 555 timer and a switch (plus power). But this does give me an idea for something that might be usefull to people. Steppers have two nice qualities, the ability to count and move at precise intervals. So a small microprocessor based circuit that could plug on the 10 pin connector to do what you asked would have several different applications.

[stevens157]

I would be willing to give something a try if you had an idea on making it work. I unfortunately don't have the electronics know how to design it. I got the idea from someone on ebay that is selling stepper driver boards that have three buttons on them for :

INC: CW run
DEC: CCW run
FUN: Stop

[stevens157]

Do you think this might work? I am not an electrical guy by any means so no laughing at my schematic. I found the timer part of the schematic on another page for an electronic controller.

Mike

[PMinMO]

Yes it looks correct. The 555 is running as an astable oscillator. I didn't chech your values for frequency. You don't really need S1, simply enabling or disabling the motor will work fine.

Keep us posted with your results.

[stevens157]

I got it up and running for the most part last night before I blew something up. I can't get the motor to run smoothly. It goes from 0 to shaking with minimal adjustment to the pot. I think it may be pulsing to fast and causing the motor have a fit. Any ideas to slow down the timer or do you think it is something else?

[PMinMO]

Sounds like you may have an audio taper pot. If it is an audio taper, changing which end you used might help. You probably really want a linear taper pot which changes resistors proportionally to rotation. You can change the 1K resistor to a higher value which will lower your top speed also. Right now your top speed is about 1400hz. Going to a 2.2K instead of the 1K would lower it to about 650 hertz, 3.1K to 465 hertz and 4.7K about 300 hz.

[stevens157]

I will play around with the resistor values tonight and see what happens. I am pretty sure I have a linear pot but I will check that as well. Thanks.

Mike

[stevens157]

I have it working pretty well now. I needed to walk away from it for a few days because I was doing more harm than good. I am not happy with the amount of adjustment that I am getting so I will play with it some more and let you know how it is going. It seems to go from very slow to very fast with little adjustment on the pot. I did get some different pots just to see if that made any difference.

A stupid question regarding the stepperr motor since I am new to this. How smoothly should they run. I get it to spin pretty smoothly but the it starts to chop every once in a while. Is that bad or to be expected?

As always thanks for the help and any sugestions.

Mike

[PMinMO]

Steppers run the worst at full step, better at half step, then it becomes a power vs smoothness issues as you go ingto microstepping.

They have an inherent issue know as mechanical resonance. It' s easiest to thing of a spring that is compressed and released, how the spring oscillators before coming to rest. That is the worst at full step.