eBay TB6560 Stepper Motor Driver Boards

[irving2008]

Sure I can save the waveforms, do you want them as screenshots or save the waveforms to an output file?

I usually do screen capture or print as PDF.

Attached are 3 captures from my L297/L298 board using the same motor at 500, 750 and 900 steps/sec on a 36v supply, wired bipolar parallel (coil resistance = 3.2ohm).

This shows the A-enable signal (blue) and the sense voltage (red). The sense voltage is directly proportional to the current in the coil (x 2), so .5v = 1A. At 500stesp/sec the RMS voltage is 0.64v, a current of 1.3A RMS, the peak voltage being 0.9v equivalent to 1.8A. You can see that the current doesn't start to flow (indeed its negative slightly at the start of the cycle which is due to the back emf/collapsing field of the previous cycle) until 0.7mS into the cycle, it then ramps up due to the inductance of the coils (these being high inductance motors i.e. not very fast) until it finally gets to the current limit and the driver goes into chopping.

At 750stesp/sec the RMS current has dropped to about 1A, the peak still being 1.8A. This is because the initial start-up and ramp is a greater proportion of the cycle time.

At 900steps/sec the current never gets to the set limit before the cycle ends... this is the fastest the motor will go at this voltage and the power output wil be low, the RMS current here is about 0.5A.

To go faster with these motors needs about 70v...

Setting Vref using the scope like this is much more accurate than adjusting it statically or relying on the overall current consumption.