Hello,
I am using a STSPIN220 and believe I may have damaged the board. I am seeking to understand what I did to avoid this in the future. When I wire the system according to its minimal wiring diagram on the page, the motor power supply is current limited for voltages below the range provided on the documentation. The current limit of the power supply is on immediately for 0 V. In hindsight I am unsure what caused this- I was driving the board with 3.3 V digital IO pins according to the STSPIN220 application note (figure 2, page 5). If anyone could help me troubleshoot the “what” or help me figure out the “how” that would be greatly appreciated. Thank you for your time.
I forgot to mention I did current limit the driver before applying the driver + MCU to the motor. The information I have on the motor is limited but I know it is a bipolar stepper motor and has a rated phase current of 1 A with a phase resistance of 4.6 Ohms. I limited the vref following the video tutorial to be 200 mV.
When I connect this setup to the motor the motor tries to move in the direction indicated in my code, and tries to switch appropriately, but no movement is observed. I’m thinking it may be stalling because I’m not applying enough voltage/current over the Vmot input.
In short, I think my problem may be reducible to this: When choosing a Vmot voltage and current output from the motor supply when everything is connected according to the minimal wiring diagram, is it okay if the motor power supply’s current is greater than the current stepper motor’s 1 A limit (e.g. VMot=5 V with a current of 3 A). I have a feeling that is what the current limiting function on the driver takes care of, but I wanted to verify before taking further action. My apologies for being verbose, I’m new to the field and wanted to include as much information as possible for clarity.
From your description, it sounds like you were not setting the current limit on your power supply high enough for your system.
A per phase current limit rating of 1A and a coil resistance of 4.6Ω suggests that your stepper motor has a rated voltage of 5V, so you should power it from at least that, preferably higher (something between your motor’s 5V rating and the driver’s 10V maximum operating voltage). If you have the VREF voltage set to 200mV, the driver will actively limit the current to each coil to 1A, so to make sure you have enough current from your power supply, you should set it to at least 2A.
Brandon
Hello,
Thank you for your response, that sheds light on the general procedure. To my understanding from the “Setting current limit” video, the stepper motor driver partially converts voltage to current, which explains why the current drawn from the motor power supply is less than what the system actually uses. Is this not the case in the lower voltage model?
It sounds like you understand the general idea. To clarify, energy is conserved, so the power into the stepper motor driver from the power supply (plus some extra losses) equals the power out to the motor. When using a supply voltage higher than the stepper motor is rated for, the driver will begin actively limiting the current by chopping the voltage through the motor’s coil (effectively running it at a lower voltage). The higher supply voltage you use, the less current it will need to supply to the driver (since power = voltage × current). As the “Setting the current Limit on Pololu Stepper Motor Driver Carriers” video mentions, there are other factors too, but that is a simplified explanation.
This is still applicable to the lower-voltage drivers like the STSPIN220. Please note that the driver does not boost the voltage to the motor. The current per phase rating of a stepper motor is the current the coil will draw at the rated voltage, so if you do not power it with at least the rated voltage, the stepper motor will not pull its rated current (and assuming the driver’s current limit is set to the rated current per phase, it will not need to kick in).
Brandon
