# Calculate current for driving multiple nema17 with a4988

I will drive multiple a4988 drivers running nema17 from esp32 using arduino IDE. How can I calculate how much current it will draw for multiple (say 10pcs, 20pcs, 30pcs and so on) of a4988 for the:

• 5v (VDD) input on the a4988?
• 12v (VMOT) input of the a4988?

It is this nema 17 motor - 17HS4023:

Voltage : 12 V
Current: 0.7 A / phase

This is what my powersupply looks like whith 1 motor

Can I simply go for the meassurment on my powersupply? Feeding the VMOT with 0.17 A and 12 v. And then for driving 10 of them: 1.7 A and 12 v?

However when meassuring the current like this:

it says 18 mA when the motor is running and 313.5 mA when it is not running using 12 volt

My idea however is to use the powersupply for estimate the current for VMOT
And then for the 5v powersupply for VDD use something like this:

or this:

And after that, simply have a look at my powersupply how many ampere it draws.
When I have the answer I can buy a non switchable 12 volt powersupply as for example this one:

Would this be a more or less trusted way forward?

Hello.

If you are trying to determine your power supply requirements then looking at the output from your supply is a good starting point. That will be more relevant here than the current between your motor and driver.

Keep in mind that the total current draw from each stepper motor can vary depending on your microstepping mode and the specific microstep position that the motor might hold at, so I would recommend applying a decent safety margin to help ensure your supply will be able to handle the worst case scenario. It looks like the regulators and power supplies you linked to all claim to handle at least a few amps, so they might be okay, but I cannot vouch for their quality or functionality. You might also consider one of our regulators or wall power adapters.

-Patrick

So it would basically be safe to assume that I need 2 W per motor?

Can I drive the VDD directly from my esp32 or will it draw to much current? Especially if I am using maybe 20 of them?

As I mentioned before, I would suggest applying a decent safety margin over what your supply is drawing now. A conservative estimate would probably be to double that, but a lower margin would probably be okay too, depending on the details of your application.

I am not sure how much current your ESP32 can source, but the VDD supply current required by the A4988 should only be a few milliamps. You could look at the current in-line with your VDD supply using your multimeter and check that against your ESP32’s documentation to get a more confident assessment of that.

- Patrick