Posted on September 01, 2015 at 09:43Hello,
I'm using an L6470 over SPI to change between two speeds every few seconds (say 1000 steps/s <-> 1100 steps/s). To achieve this I am issuing the Run command alternating between my two set points.
I have noticed that every time I swap speeds the current reduces very slightly. After my application has been running for an hour the current has reduced to such a point where there is no longer enough torque to turn the motor. Setting the motor to 0 steps/s (again using the Run command) and back causes the current to return to normal. If I leave the motor to run at a constant speed, there is no change in current over the time period. Stopping the motor between each speed change is not ideal.
To debug this problem I have tried to remove all status polling and that did not help. I also ensured that there is no erroneous SPI commands being sent using a logic analyser. I have also ruled thermal problems by using freeze spray on the L6470 chip. And I on't think it is a power supply problem. The rate of decay of the current through the motor is proportional to the rate I send through the run command.
Any ideas what could cause this behavior?
Thanks
Edit:
I was able to reproduce this behavior using dSPIN and EVAL6470H-DISC. I have attached the script and register configuration.
#l6470
