Hello, I am using an ESP32 Huzzah from Adafruit with 2 NEMA 17s and DVR8825s. How do you guys power this circuit? With a bench power supply, batteries, AC adaptor, or something else? Something that can give enough voltage/current to both and steps arent skipping.
NEMA 17 tells that M3 screws are used for attaching the stepper mechanically but tells nothing about the current it can use.
drv8825 Max Amp = 2.5 at 24VDC
2*2.5 + current stepdown converter to power ESP32 so I would choose a 7.5Amp 24VDC power supply
It is very important to adjust the current to match the motor specs.
Adjust stepperdriver current
Well I use 2 NEMA23s from a 24v 2A power supply driven by 8825s. There is also a 5v 4A output on the supply that runs a UNO and the 5v on the CNC shield.
You don't have to set the stepper current to the max for the driver, or the motor!! Even if you do, that's the MOTOR current and the current from the supply is much less since the driver is in effect a step down switched-mode converter. Follow the 8825 instructions in the Polulu video on their website and set the current to get enough torque for your application. I doubt that the stepper coil current will be much more than 0.5A and the supply will be much less. A 7.5A supply would be drastic overkill. One of my 23s is driving the X table screw on quite a big mill and only uses about 0.5A.
NEMA 17s can use M3 screws but I have one that uses UNC screws. The 17 actually refers to the dimension of the lamination stack which is ~1.7 inches.
It depends on the motor, the load and if you are using micro stepping. A 17HS6001S 0.7N for instance needs with max load 2.3 Amp without micro. Besides, the difference between 48W and 150W is less then 15 Euro's.
That's the coil current. And it refers to each of the coils. As @jhaine already pointed out, that's NOT the current from the power supply. The PSU current also depends on the voltage: the higher the voltage, the lower the current.
If you have a current driver like the DRV8825, you must compute the necessary PSU by means of the needed power of the stepper, not the current.
Hi, @fazeall
Can you please post a link to specs/data of your stepper motors?
Thanks.. Tom... 
Thanks for that. A good explanation of this is about 7 minutes into the video here:
In that example the coil current is set to 1A peak but the supply current was only about 0.3A from a 12v supply. From a 24V supply it would be significantly lower. It's all to do with conservation of energy.
Yes, that's it. And that's why you need a large capacitor at the power input of the driver. Most of the energy oscillates back and forth between the coils and this capacitor. The power supply "only" has to provide energy for the mechanical work and the ohmic loss in the coils ( ok, the efficiency of the driver isn't 100% too 
)
I believe its a 17HS4401S going by the Amazon listing I bought it from, which has its specifications
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