want to use current control via SPI on old miniPCB versipon 1.275, big tree tech tmc5160 version 1.2, do i put shunt on axis 1 aux1-m3 and axis 2 aux2-m3

Ming Lord

I am repopulating old miniPCB 1.275 with teensy 3.2. 
I have bought 2 bigtreetech tmc5160 version 1.2. I want to use SPI mode to limit current to my steppers. in the old days i had to add shunt across axis 1 aux1/m3 pins to enable spi smoothstep in tmc2130's. do I do this with tmc5160? it has the SPI pins sticking out over motor driver, I dont need to wire these into the aux1/m3 pins?
Or can I just plug tmc5160 in and set-up in onstep software? wiki mentions disconnecting clock pin on bigtreetech tmc v2, is that correct? Apparently the version I have has clck pins grounded. So do I still cut pin off?
The current version of onstep sortware is it only working for modern versions on minipcb ie v2? Has pinout changed a lot?
Sorry for hard to understand text. I am sure can work most of it out but want current to not be full power and blow up my teensy or drivers as dont have spares :)

Ming Lord

To clarify: 
in the design notes for the minipcb v 1.27:
OnStep Mini notes for Rev. 1.27x PCB:

It is stated that for tmc2130:
'Choice of Stepper driver:
SilentStepStick TMC2130 (read about the TMC2130 before buying!) is the most advanced stepper driver supported (operates in SPI mode.)  Many options are available with these drivers, see OnStep's configuration file.  Additionally, Aux1 and Aux2 can be used to carry the SPI SDO (data out) signals from the drivers to the Teensy and allows OnStep to query the stepper drivers about their Fault status.  This is enabled by using a shunt on headers J5 and J10.  The shunt should connect AUX1-to-M3 (Axis1) and AUX2-to-M3 (Axis2.)'

My stepper motor is 400 step nema 17 bipolar, 2A.
I'd like to run the stepper at close to the 2A off a 12v or 19v supply. I am worried about it burning out, especially as no heatsink is said to be required, if I dont wire up the SPI part correctly.

Thanks Chris

Drew 🔭📷🚴‍♂️

On Thu, Oct 21, 2021 at 01:52 PM, Ming Lord wrote:
I'd like to run the stepper at close to the 2A off a 12v or 19v supply.
Why?  Running a stepper at its maximum current has no advantage. These steppers run the best at 30 to 70% of their maximum power.

If you actually require so much torque it tells me that you have other issues. The mount may be mechanically unsound (old lube, etc.), unbalanced or too large for this setup.

Running at maximum power will only generate a lot of heat and increases the chance of destroying the mount if anything goes wrong.

In practice the Fault status option is of little use and can cause problems of its own (it often generates non-existent errors).

Most of the mounts used here perform well with the Motors you are using. Mine operate a Meade LXD75 with a 25lb. scope at 60%.

Drew 🔭📷🚴‍♂️

On Thu, Oct 21, 2021 at 12:48 PM, Ming Lord wrote:
do I do this with tmc5160? it has the SPI pins sticking out over motor driver, I dont need to wire these into the aux1/m3 pins?
No, the TMC5160 is controlled by OnStep. I cannot comment on this particular board but it should be plug and play. The clock pin should be OK as is.

Also, the TMC5160 has separate output mosfets. This makes it one of the coolest operating drivers.

Ming Lord

Dont want to run at maximum power really, 70 percent or whatever is fine, just as ive been out of loop for 3 years Ive forgotten a lot of the details of onstep and the new drivers sound great but cant afford to wire them up incorrectly and burn them or teensy out by mistake.
Thanks for reply.
My mount is a really old heq5 that Ive ripped motors and board out of, angle ground room for 2 nema17's inside the mount, but space for build is very tight, so tnc5160 needing minimal heatsinking very attractive.

Howard Dutton

On Thu, Oct 21, 2021 at 06:41 PM, Ming Lord wrote:
so tnc5160 needing minimal heatsinking
I think you will be surprised at how cool they run, seriously doubt the need for any heat-sink at that ~2A level.

George Cushing

As Drew says, start with something like 1 amp. On the MiniPCB1 SPI driver control is enabled. See this https://onstep.groups.io/g/main/wiki/3862 for details.