Stepper driver voltages

[old man emu]

I've just replaced all the stepper drivers on my RAMPS board with Stepstick drivers. Dr Luigi (Professor of Printology) said that the Vref for these stepper drivers is 1.28V. I set all my steppers to this and three of the five motors sang like canaries. The two Z-axis motors didn't move at all. As I still had the Pololu driver, I refitted it and set Vref to something like 0.34V, and then these steppers joined the other song birds.

The Steptsicks were brand new, and selected at random for fitting. Anyone want to hazard a guess why a new driver would not fire up a pair of motors? I had read something about having to double the Vref when driving two steppers off the one driver, but that doesn't make sense because the Pololu I used was set at the Vref for a single motor.

Trying to find detailed information on how these stepper drivers work is near impossible. The manufacturer's site only gives enough information to get the things functioning.

Old Man Emu

[1stage]

Hey OME,

A friend who owns the earlier Makerfarm Prusa i3 said that to calibrate his steppers...

"I did adjust the motor drive current, and found that it made it WAY quieter. Use Pronterface for that. Drive an axis, turn down current until it skips steps, then turn up until it runs smoothly...then a bit more for margin."

Does this alternate method work better, worse, or about the same? Sounds easier, at least. You still have to tweak the pots on the drivers, but you don't have to risk a short when trying to get a voltage read with the multimeter...

[old man emu]

Using the multimeter is a lot easier that going back and forth to Pronterface. I have relocated my RAMPS board to the top of my printer, beside the LCD. That allows me to work over the top of the board, and I can control my screwdriver position better. Also it is imperative that the steppers are disconnected when the adjustment is made to avoid electrical shorting.

I've got the adjustment process under control. My question relates to the failure of the Stepstick to drive two steppers, where the Pololu can.

OME