This is a PCB made to act as a mainboard for three pieces of the DRV8825 modules (http://www.ti.com/lit/ds/slvsa73f/slvsa73f.pdf
) that can be bought from here: https://www.pololu.com/product/2133
or can be found on: http://www.aliexpress.com/wholesale?catId=0&initiative_id=SB_20160611030054&SearchText=DRV8825
The modules work very well for a medium sized CNC router, using NEMA23 motors rated at 3A. Of course the current offered by the DRV8825 is lower than that (max 2.5A) but the current is limited by the module.
They are sitting on sockets made from female pin headers.
As you can see I mounted a fan over the modules but what it can't be seen is the fact that I actually soldered some pieces of copper sheets on the back of DRV8825 modules (there are some thermal vias there) and then turned them in such a way that the flow of air from the fan will pass over that copper in order to cool better the DRV8825 modules.
Each DRV8825 module has also an aluminium radiator glued onto it.
The fan is powered through a already made board (PWR_B1 on the schematic, see marked with yellow in schematic pic below) with LM2596 (like this one: http://www.aliexpress.com/item/1pcs-DC-DC-Buck-Converter-Step-Down-Module-LM2596-Power-Supply-Output-1-23V-30V-hot/32608665884.html?spm=2114.01010188.8.131.52TWbIO&ws_ab_test=searchweb201556_10,searchweb201602_4_10037_10017_507_10032_401,searchweb201603_2&btsid=b90d78d9-9411-40e8-83cb-78e21360e546
The advantage is that I can adjust the speed of the fan and find a compromise between air flow and noise.
The board looks like this:
and the schematic:
Attached is an archive (usual password) that contain the following:
- Eagle design files
- manufacturing files (GERBER files, GCODE drilling file, PDF's with negative films for UV exposure)NOTE
The DRV8825 module from Pololu come with mixed decay as default and that can cause missing microsteps. Make sure to disable this mode on the modules and select FAST decay as this mode is safer although it will introduce some motor noise (whining) especially when they are not moving. http://forums.reprap.org/read.php?160,566688
Another solution that work with mixed decay (default mode) is given here: http://cabristor.blogspot.ro/2015/02/drv8825-missing-steps.html
I mounted the fan cooler on the board using some "pylons" made from aluminium sheet cut in strips of about 5...7mm thickness and then I bent the ends 90 degrees and drilled a 3mm hole for the screws in both bent ends. Made 4 pcs for the cooler and used some plastic washers between the "pylons" and the board.