Re: Versions of LV8729 Stepper Drivers


Michael E. Burk
 

All the other mega2650 boards will work five, they supply 5volts to the stepper drivers.


On Sat, Jul 13, 2019 at 10:00 AM Khalid Baheyeldin <kbahey@...> wrote:
On Sat, Jul 13, 2019 at 11:18 AM, Michael E. Burk wrote:
We found when upgrading 3S printers from MKS GEN L v1.0 to BIQU SKR v1.1 or v.3 that we could not set the Vref higher than 1volt with the FYSETC LV8729's. Only the MKS could we set higher.
I changed to a LERDGE K board and then they worked fine. 3.3volt logic verses 5volt logic.
Logic or power? Logic should not matter, since the STM32 pins are at 3.3V, but they can interface with 5V
modules with no issues (e.g. WeMos). The PCB is powered by 5V.

The Vref forumla is different:

100 resistors: Amps = V * 0.5 (MKS is always 100 it seems)
220 resistors: Amps = V *1.1 (FYSETC 220)

Did you take this into account?

I think we need to verify the above observation (not being able to set Vref higher than 1V) on the OnStep
boards.

I just tested the 220 FYSETC ones, and I can go up to 1.69V. So no issue with the STM32.

Can someone who the same FYSETC check on an MKS Gen-L?

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