Pololu Standard Stepper Drivers are Costly and Time Consuming

[sphawes]

Version Number

REV04

Bugfix or Enhancement

Enhancement

Description

The TMC2209 stepper drivers in the Pololu stepper driver format have worked well, but they are very costly, depend on a company to source (are pseudo-open), and require two 1x6 THT headers and one 1x2 THT header for each driver for a solid connection.

They also appear to be using the TMC2209's internal shunt resistor, which is less than optimal for measuring current accurately.

Suggested Solution

Implement stepper drivers on the motherboard itself. Although this means drivers are no longer swappable, we have seen almost no instances of bad drivers, and the ones we did were a result of them being DOA from the manufacturer.

We'll also use a much easier to inspect/solder variant of the TMC2209, the TMC2226. This chip is identical, except for the package which is much larger and has legs.

We can also use large, accurate shunt resistors for a better measurement of coil current.

[warasilapm]

Maybe I'm a weirdo, but IMO the TMC2209 QFN is the better part between the two. It's more compact and just as easy to solder/inspect. If anything, I actually find inspection easier since the QFN is side wettable and there's no foot fillet to worry about. I also find QFN self-centers far better, at least in my experience.

Just my two cents - I was going to suggest the 2209 when I saw the layout and then when I went looking for duplicates I saw this reasoning here. Totally up to you; you know your process better than I do.