The power supply is a 24Vdc 5A.It's a Tenma 72-2540
The motor vibrates instead of rotating... I think problem is on the motor side.
I don't have a datasheet of the motor. :
Good news
Changed the motor and now it's working
Fantastic! That tacho output is useful too , consider using an interrupt pin on the Arduino and you have rpm feedback.
I want to use an Arduino Zero;
Can I connect the tacho directly to a digital input? Or do I need some
hardware in between?
I didn't use anything with an atmeg328 just straight from the tacho output to the arduino, a 1k or 2.2k resistor may be wise.
The tacho output I believe is the same voltage as VDD for the a4960 so you will have to make sure the voltage levels are ok for whatever pin you are using on the zero.
Ok
Another question the thermal PAD of the A4960 ?Do I have to connect it to GND?
It is probably wise to, its not internally connected to ground and does not need it to function but the thermal pad should be soldered to some copper pour to dissipate heat.
I just left it unconnected as I was hand soldering, the chip never got even warm, but that was in a high airflow environment.