CNC Cyclone PCB Factory: Arduino CNC Shield, stepper and driver – Part 2

Electronic: Introduction

For electronic I’d like to use Arduino with CNC Schield v3 (with 3 stepper driver), It’s open and cheap.

I take 3 mechanical end stop switch as described in the original project (the third one is for renewed Z axis).

3 stepper nema 17 (form factor is important to fit on printed part), if you have some old printer at home now It’s the moment to disassemble It.

A bluetooth module like ones described in this article It must be an serial pass-through module, not BLE one.

A relay module, a mosfet for additional/future use, 4 buttons, 2n2222a transistor and some capacitor.

Wire, some dupont (male and female), 2 crocodile clip.

A power supply, 12v 10A It’s sufficient.

Electronic: CNC Shield

You can find this CNC Shield at low cost.

You can find here AliExpress

This is a shield for Arduino UNO, but some Arduino have problem with serial communication with grbl program, in particular some CH340G usb serial connection doesn’t work.

My personal experience I have had some problem with micro-usb arduino, but no problem with “standard” arduino USB port (even if It was CH340G).

You can find here Arduino UNO - Arduino MEGA 2560 R3 - Arduino Nano - Arduino Pro Mini

For this project is preferable to remove all jumper on shield because threaded rod work as demultiplexer then with divider became to slow.

Electronic: Stepper Driver

You can find here AliExpress

I choice A4988 driver instead a more powerful and precise DRV8825 for 3 reason:

• A988 cost less;
• We don’t need 1/32 step divider;
• My motors (taken from old printers) have less than 2A phase.

There is a simple “trick/way” to set correct amperage, you must put tester + on potentiometer and tester – to GND of the driver (look the image) then:

• DRV8825: Imax = 2 * Vref (if Imax = 1.5A, then Vref is to be set to 1.5/2 V = 0.75V)
• A4988: Imax = 2,5 * Vref

In my situation I put 0,8v*2,5 = 2A even if the step amp phase is 1,7amp but I need more power.

Stepper motor

For this project the spetter needed is Nema 17 with 200 step.

You can find here Aliexpress

The wiring schema is quite simple:

Identify coil of 6-wire stepper motor

Most of the motors taken from the printers have 6 wires not 4, so it is important to recognize them to be able to use them as 4-wire bipolar.

I’m write this article to explain how to wiring the stepper.

Thanks

In the next part we are going to show limit switch and the problem of noise.

1. CNC Cyclone PCB Factory: mechanics
2. CNC Cyclone PCB Factory: CNC Shield, stepper and driver
3. CNC Cyclone PCB Factory: limit switch
4. CNC Cyclone PCB Factory: probe and relay
5. CNC Cyclone PCB Factory: control panel and bluetooth
6. CNC Cyclone PCB Factory: boards schema and other
7. CNC Cyclone PCB Factory: settings and tests