# How to calculate required amperage of multiple motors?

I a very simple question about calculating the amperage I need to run 5 stepper motors from my Arduino Uno.

If I have 5 28BYJ-48 stepper motors(which are 5V and are said to require about 240mA each) all plugged into 5 separate ULN2003 driving boards, and I wire 4 signal wires from the boards to the Arduino, and connect the two power wires for the board to 5V and GND on the Arduino. What voltage and amperage I need to supply to my Arduino for everything to run properly?

I'm worried because I read that the Arduino cannot handle over one amp but 0.24*5>1, although I don't know if the amperage is additive with each additional motor.

• your question is not about the arduino ... it is off topic here May 1, 2021 at 18:20

I don't know if the amperage is additive with each additional motor

the Arduino cannot handle over one amp but 0.24*5>1

That is correct. But the stepper motors should never be powered through the Arduino. You should connect a fitting power supply directly to the stepper drivers. That way the needed current flows past the Arduino, not through it.

What voltage and amperage I need to supply to my Arduino for everything to run properly?

The Arduino runs at 5V, though you can provide 7-12V to Vin/barrel jack. When your motors are rated for 5V, you should provide them with 5V. So it would be fitting to buy one 5V power source to power the Arduino (through the 5V pin or USB) and the stepper drivers.

For the current: A good measure is the stall current of a motor, so the current, that flows, when the motor is driven, but cannot move (due to being physically stuck). Add a bit headroom to this. The mentioned motors are often badly documented, so that you might not be able to find a stall current value. Add more headroom in that case. So I would suggest adding up all the amps and then multiply this value with 1.5 or even 2. Let's take 250mA per motor (for ease of calculation) with 5 motors gives 1.25A. Take at least a 2A power supply. When you want to make sure go directly to 3A. The price difference in that range isn't that much anyway.

• Super helpful thanks lot May 1, 2021 at 21:53
• You said it would be fitting to have a single 5V/2-3A power source for both the Arduino and the motors but can't the Arduino not take over 1A May 3, 2021 at 23:19
• @KidWithComputer Current is different than voltage. While you need to provide a specific voltage, the current of a power supply is only a maximum, that it can supply. The Arduino will only draw the current, that it needs to work, from the power supply. You could easily use a power supply capable of hundreds of amps, it would still work. The 1A current limit is actually meant for the situations, where you power components through the Arduino, so the current is flowing through it and its components and PCB traces can only handle max current. But this current would be drawn by other components. May 4, 2021 at 7:13