Hey guys new to the forum, i have just purchased 3 nema17 steppers, a cnc sheild v3 and 3 A4988 drivers but im unsure what is best to power the cnc sheild woud 12v 5A be ok then limit the outputs on each driver?
My microcontroller is a arduino uno.
Here is my cnc shield:
ALMOCN 3D Printer CNC Shield Expansion Board with 4pcs A4988 Stepstick Stepper Motor Driver Module for 3D Printer https://amzn.eu/d/hZo6vRe
Any help would massively help as i dont wont to fry my kit!
Here is the power supply im thinking of getting:
12V 5A 60W AC Adapter Switching Power Supply with 5.5 X 2.1 mm DC Plug and 11 PCS DC Jack Connector for led Light Strips, Computer Monitor and More https://amzn.eu/d/feTwSUJ
And my stepper:
Twotrees 4 lead Nema17 Stepper Motor Nema 17 motor with 1m Cable 42BYGH 38MM 1.5A (17HS4401S) Motor for CNC XYZ 3D Printer (3 pack) https://amzn.eu/d/ji2TH2V
That 12V/5A supply should be fine to run those 3 motors.
The stepper drivers control coil current. You can use a supply with an output voltage up to the maximum allowed by the drivers (35 V for the A4988) The current does not matter as long at it is enough to supply the motors properly. You could use a supply of 100A or more and as long as the voltage is under 35V and over 8V (A4988) and the driver coil current limits are set the motors will be happy.
Your motors are specified at 1.5A max coil current. The A4988 stepper drivers are only good for 1A unless they have a heat sink and forced air cooling, then they can handle 1.5A if they are quality parts. Chinese clones may not be as robust. The DRV8825 drivers are good for 1.5A without a heat sink. You might want to consider getting those. They directly replace the A4988.
How are you going to supply the Uno.
It is imperative that the coil current limit on the stepper drivers be set correctly. Set the current to less than or equal to the spec current. The motors that you have are specified at 1.5A which is too much for an A4988 without heat sink and active cooling. To set the current limit you will need to know the value of the sense resistor on the A4988 driver board. Then enter the value of the resistor and the required coil current into the formula Vref = Imot x 8 x Rsen where Imot = the coil current and Rsen = the value of the sense resistor. The Pololu A4988 page covers how to set the Vref but you must use the sense resistor value on YOUR board. This page shows how to locate the sense resistor.
Setting the coil current to less that the max is OK as long as the motor performs properly and does not miss steps. The motor and driver will run cooler and last longer.
Those CNC shields are great. I have a few. They make building CNC machines a lot easier.
What are you building? Are you going to use Grbl or write your own code?