Homebrew Allegro uStep Driver

My first real post on the forum, other than my 'hello' thread some time back...

Thought I'd post a couple of pictures of the pcb I assembled this evening. After completing a design for a customer recently, I had some Allegro A4983 and A4988 35V 2A microstepping driver chips going spare. Since my Peatol mill currently lives with 1/2 step drivers, that seemed like a bit of a waste...

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I only had 1.2A motors in the lab, but it's been running nicely all evening (from a pulse generator) set to 1.5A. It's a very basic design, made almost entirely from junkbox parts. There's no isolated inputs or protection circuitry, though there are emc filters on the outputs. This board has a A4983 device fitted, but the ones destined for the mill will use A4988, which run smoother at low speeds.

The pcb is 0.8mm double sided, 50mm x 50mm, and the final versions will be mounted on some cheapo pc processor heatsinks, machined to suit - overkill, but about as cheap as bolting them to a bit of plain plate.

Partly it's an experiment to see how robust the Allegro drivers are when operating at the limit (in my commercial design they run at around 1A maximum, and the total dissipation is limited by reducing the holding current), but also it gets me a cheap set of microstepping drivers :heehee:

I've got to respin the pcb for the best thermal performance (I c**ked up the ground plane on the back of the pcb) and then I'll get them on the mill and see if I can let the smoke out :smile:

Dave