I am using the TIC Ctrl Ctr program to check out a stepper motor (SY57STH41-1006A) function with a T500 controller (firmware 1.06). Basic functions are good but trying to see how fast the motor can spin at constant velocity is giving me problems. The current limit is 174mA but as I increase the limit the motor can only spin slower and slower before it stops. I don’t understand why increasing the current limit gives less top velocity. I can’t get the limit anywhere near the 1000mA and function? The Vin from the PS is staying at its 12 V rating.
Hello.
That seems like a strange behavior. Can you post more details about the power supply you are using? What current limit does the stepper motor stop at?
Can you post pictures of your setup that show all of your connections as well as your Tic settings file? You can save the settings file through the “File” menu of the Tic Control Center while the Tic is connected.
Brandon
I will send the settings and a photo soon.
Today I changed the PS from 12V to 18V and the top speed increased from 300 to 600 RPM but that was with the current setting at 174 ma. When I change the current limit to a higher value the max RPM decreases rapidly. The stepper motor docs show 1 A current limit. I seem to get good results in position mode but in velocity mode I was expecting a higher max speed and not expecting to get higher speeds with lower current limits.
I did monitor the PS current during velocity testing and as I increase the speed the current decreases and it seems to get to a point where the current to the motor cannot sustain the motion and then the motor stops. Voltage in from PS is not dropping. I am using switching power supplies.
From the pull-out torque curve in that stepper motor’s datasheet, it looks like the available torque drops off fairly rapidly after 300 RPM, so you might not be able to get very consistent behaviors at speeds like 600 RPM.
What microstepping mode are you using and what step rates you are able to get when you increase the current limit to a few different levels (i.e. how fast can you step when the current limit is 300mA, 500mA, or 1A)?
The current draw when stepping at faster rates is usually lower than when stepping at slower rates. This post on StackExchange has some details about why that occurs. Can you post more details about your power supply, such as a datasheet or a link to a specs sheet? The settings file and pictures of the setup would still be helpful, too.
Brandon
Appreciate the help in understanding this and I think I have a handle on it now. Paying more attention to the torque curve helps alot.
It looks like I am bumping up against a limitation of this particular motor. I increased the PS Voltage to 32V and was able to ramp up the max velocity to 1000 RPM if I reduced the max acceleration and set the current limit to 174 mA. More acceleration or higher current limit resulted in a lower max RPM.
When I run in position mode it will draw the full 1 A at the 990mA current limit setting and changes position quickly so it seems to be working properly.
This will get me going as I am using this settup to learn how to write basic motor control software and how these stepper motors can work.
Thanks again for the help. Glad that I purchased from Pololu - the level of documentation and available help is what made the difference.