Wouldn't all the 30A go through just one motor?
Just connect all your motor drivers in parallel to the power supply. You can also draw power for the Arduino from the power supply.
It does not matter if you have "too many" amps. Each device will only take what it needs.Under NO CIRCUMSTANCES should you draw power for your motors from the Arduino board.Just connect all your motor drivers in parallel to the power supply. You can also draw power for the Arduino from the power supply.You have not provided a link to the datasheet for your stepper motors. You may find that a voltage higher than 12v would be better for driving the motors....RStepper Motor BasicsSimple Stepper Code
Pardon me if you already know this, but it seems you may not. Pardon the analogy, too. If you hang all your socks (ie, motor drivers or other loads) on a clothesline (power supply) to dry they're all in parallel connected to the line. Think of the clothesline as Vdd. As long as the clothesline is strong enough to support the load (current capacity) without snapping you're OK.On the other hand, if you connected one sock to the line and another to the free end of that one and so on, they'd be connected in series.
Image from Reply #3. See this Image GuideYes, That is the correct way to connect the drivers in parallel. But UNDER NO CIRCUMSTANCES connect 12v to the Arduino 5v pin. Either connect the 12v to the barrel connector or use a regulator such as a 7805 to provide a suitable 5v power supply for the 5v pin.Also NOTE that in the diagram in your Original Post there is a large capacitor at the motor driver input pins - you don't have them in you diagram....R
47uF 16V 105C Radial Electrolytic Capacitor 5x11mm
Electrolytic capacitors are very clearly marked with a minus sign on the side with the negative terminal. Make sure to get capacitors with a voltage rating that is 2 or 3 times higher than your power supply voltage....R