Need help with NEMA control

[The Gresley Luthier]

Hi All.

I have a project to drive a NEMA 17 using either Push Buttons or a Potentiometer, i have tried several videos on you tube to no avail.

Can anyone help me??

Regards

Ray

[JohnHaine]

Hi Ray, I think you are taking the wrong approach using either buttons or a pot with a stepper. You would still need some way to to position the carriage accurately which might as well be a DRO in which case you don't need a stepper; OR you need some way to count how many pulses have been sent and display it.

What you need to do is send a precise number of pulses to the stepper to get your required movement, knowing the pitch of the leadscrew. I think somewhere else you were asking about using an Arduino to drive an A4988 stepper driver? If you do want to take this approach I suggest the following.

1. Use an Arduino Uno (the original basic version) with a CNC Shield (Google it). The shield mounts on the Arduino and takes one or more A4988 or compatible drivers. You will need a 5V power supply for the Arduino and something like 24V for the stepper driver.

2. On the Arduino run GRBL - this is free CNC motion control software which is very capable, used in many 3D printers and low cost routers.

3. Then you need to send GRBL g-code commands to configure it (once) and to make it move the stepper the required distance - I assume this might be different for each fret? When you configure GRBL for your axis you tell it how many pulses are needed per millimetre, so the command to move say 13.5mm is just G1 X13.5.

The commaands can be sent from a phone app such as GRBLController (Google Play store, again free) using Bluetooth, or one of many other free PC apps over USB.

I know this approach works as I have used it to control the powered cross-feed on my milling machine. Using a ball screw would be nice but probably not necessary, for this application cheaper trapezoidal leadscrew would probably work, or you might get away with M6 stainless studding as I did on a CNC coil winder.