The fan voltage is provided by a 7812 Voltage regulator on tinyG. The input to VR is Vmot, usually 24V.
The 7812 is rated at 1A, but that rating is depended on thermal environment.
The 7812 used the tinyG ground plane as a heat dissipator, sharing that with the heat slugs in each of the motor drivers.
So at 0.5A draw, the 7812 will be dumping 6Watts of heat into the tinyG, which will warm things up. For sure, one of those fans should be dedicated to providing excellent airflow for the tinyG board itself.
If you are a heavy duty user(NEMA 23s or larger, long jobs, etc.) I’d suggest you seek out another solution. Perhaps a dedicated Vmot to 12V dc-Dc converter rather than a linear regulator, or perhaps a dedicated 12V wall wart for your fans. Or 24V fans (somewhat more expensive). Or perhaps supplemental heatsinking for the tinyG board.
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