L6470 FS_SPD does not switch properly

[peterjakacki]

Posted on March 26, 2012 at 07:32

There seems to be an error in the datasheet concerning FS_SPD. For starters the maximum value is h3FF and not hFF as stated. But if I am running in 128 microstep mode and the FS_SPD threshold is crossed it does not actually switch to full-step mode, it looks more like an in-between microstep mode. I have confirmed this on the scope, it's not the same as running the motor in full-step mode.  BTW, I have managed to run the NEMA34 at up to 3400RPM.

#l6470 #l6470

[Enrico Poli]

Posted on April 05, 2012 at 11:24

Hello,

the what do you exactly mean with ''''in-between microstep mode''?

When the voltage mode driving operates in full-step, the motor phases are driven with a

voltage

 square wave, but the BEMF is still sinusoidal. The resulting current is not the current square wave obtained by current mode control, but is very similar to the waveform you obtain when the current mode reaches its driving limit (something like the charge and discharge of a coil).

Voltage mode driving main advantage is the smoothness, so it does not give the best results when full-step is used. The full-step/voltage mode pair should be used in particular scenarios only.

If you want you can post your waveforms, so we can check if some other issue is present.

Kind Regards

Enrico 

[charlescharles9]

Posted on July 17, 2012 at 11:50