I have been experimenting with the DRV8811EVM. I have a question about the Current Control parameter on the GUI. I have the control set at 1345 (displayed number when you drag the pointer on the screen). My 12 VDC power supply has an ammeter on it and sometimes the draw is about 1/2 amp when the motor is operating and other times it is much less (barely shows on the ammeter). The stepper motor always seems to be operating consistently although I see two considerably different current draws. This same behavior occurs sometimes when the motor is at rest--sometimes the ammeter shows about 1/2 amp and sometimes it barely registers. It is almost as if the ammeter is intermittent because the pointer still says 1345. I have tested the torque for both conditions (1/2 amp reading and low current reading) and there appears to be no difference in motor performance. When the ammeter is reading about 1/2 amp and the motor is at rest, the current drops slightly when the motor is running. I have touched the DRV8811 chip and its temperature "feels" about the same for both cases (not hot at all). Can someone educate me on this?
I am using full-step mode, decay control is set to 0, Pulses Per Second is set to 700, and I am using the "Move Steps" function. Power supply is 12VDC. My stepper motor is an Applied Motion # HT17-275 http://www.applied-motion.com/products/stepper-motors/ht17-275 connected in the "bipolar series" configuration.
Thanks in advance.