AtomCNC - Revision 1 · AtomCNC is a CNC Controller based on GRBL. It can control up to 4 axes in 2 different configurations, a XYZA type configuration where you have 4 separate axis

AtomCNC - Revision 1.2

AtomCNC - Revision 1.2 Http://AtomSoftTech.com Page 1

AtomCNC

What is it?

AtomCNC is a CNC Controller based on GRBL. It can control up to 4 axes in 2 different

configurations, a XYZA type configuration where you have 4 separate axis or a XYYZ

configurations where you have 4 axes but it behaves as if there are only 3 by cloning the Y axis

onto a secondary Y2 stepper. This allows for doubling of the steppers on Y axis for a more stable

solution in some CNC models.

The AtomCNC is customizable and easy to use. It has a nice CLEAR easy to read silk screen, so

there is no need to pick up a manual or open a PDF to wire this board up. The board uses 4x

A4988 controllers from Pololu to control the stepper motors. The layout allows the controllers to

be replaced with no soldering skills if a problem should arise. AtomCNC also includes an on

board 10A 240VAC relay to switch on and off the spindle. The main MCU is an Atmega328

using the Arduino Uno (opti) boot loader. Which means there is no programmer needed for

future firmware upgrades and replacement parts are easy to source.

Here are some features:

1) Atmeg328 - Main controller (NO PROGRAMMER REQUIRED!)

2) 4x A4988 - Stepper Controllers (X,Y,Z,A/Y2)

3) 240VAC @10A relay for spindle control

4) CP2102 - USB to UART for Programming and Control via PC/Linux

5) XYZ Homing / Limits

6) 3 GPIO ports for custom attachments

7) Selectable at time of purchase: USB TYPE B or MINI B connector. (Default is Type B)

8) Sturdy Terminals to connect your steppers.



Hardware Below you will find schematics of the hardware. A detailed part list will be available at the end of this

document. Also included with this document should be a BOM and Schematic file. (Eagle 6+)

There are 3 portions for the schematic.

1) MCU Control

2) USB & Power Control

3) Stepper/Spindle (high power) control



1. USB to UART & Power Control

a. USB to UART is done via CP2102 IC. It handles all communications between the PC and

PCB.

b. Power is mainly supplied through the USB connector, but can also be combined with

the power Jack connector. (2.1mm)

c. Power is fed through a BAT54C which is a Dual Rectifier (Common Cathode). This allows

2 different power sources to be fed into 1 power rail without having to worry about

feedback or 1 power source overriding another.

d. Input from the Power Jack is decoupled using a 10uf and so is the output from the

LM1117 (5v) Regulator. Every IC, MCU or sensitive device is also decoupled with 100nf

capacitors and 1uf capacitors where needed.



2. MCU Control: Features

a. ATMEGA328P controls all operations. Clock is a 16 MHz crystal.

b. Reset button and Power Led.

c. Can control up to 4 axes. X, Y, Z and also A or Y2. Y2 is used with dual Y axis.

d. X,Y,Z homing capabilities. Can double for Limits as well.

e. 3 GPIO for future update. Such as A/Y2 homing.

f. Rotary On/Off control. (10A @ 240 relay rating)

g. GPIO and Homing/Limits are all pulled high with 10k resistors.





3. Stepper / Spindle Control

a. Steppers are controlled by up to 4 A4988 Allegro controllers. (Pololu)

b. Each controller is decoupled with a 47uf, 1uf and 100nf capacitor. For smooth transactions.

c. Each controller can be configured individually via

onboard jumpers for 1,2,4,8 or 16 steps resolution.

M = X,Y,Z,A/Y2

d. Since homing and limits are pulled high on the PCB,

actual switch polarity is not an issue.

e. CPU Fan (50mm) mounts are provided to help keep

the controllers cool while in use and is HIGHLY

RECOMMENDED!

f. Rotary control is done via a 10A 240VAC relay.

g. A or Y2 selection is done via JP5.



Selecting the 4th Axis

The AtomCNC provides 2 options for a 4th Axis. You can either have an “A” axis or “Y2” axis.

The A Axis can be used for 3D printers or Pick & Place machines.

The Y2 Axis is usually used when you need more torque or stability on the Y Axis. It will mimic the Y axis

to another stepper.

Selecting between the 2 is a fairly simple task.

The image on the bottom shows how to set the jumper for “A” axis control.

The image on the top shows how to set the jumper for “Y2” axis control.



Installing a Fan

Parts needed:

Qty Item Details

2 Bolt 6-32 x 2 ½”

4 Nut 6-32

2 Wing Nut 6-32

Fasten bolts to board with nuts. Then use 2 more nuts to set the height of the fan. It should be around

the height of the Relay.

Place bolts through fan holes and use wing nuts to secure the fan in place.



Connections

Wiring up your AtomCNC isn’t as hard as you may thing. Here is a color marked view.

Stepper Motor & Stepper Power Stepper Motors usually come with a RED/BLUE & GREEN/BLACK pair of wires. Using the below its easy

to see how to make the connects. The VMOT and GND are stepper power input from your external

supply. Usually 24v @ 5A.

Dremel/Rotary & Power The Dremel & Line are used for controlling the Dremel or Rotary tool. Line is INPUT and DREMEL is the

output. Be careful as this is ****HIGH VOLTAGE****



GPIO & Limit/Homing Connecting Limit/Homing switches is as simple as connecting a button. There is no need to worry about

pull-up resistors or connecting which power line to the button. There are 2 pins for each button/GPIO.

All GPIO/Limit/Homing are pulled high on the board. This makes connecting external peripherals a cinch.

Most Momentary switches come with 2 pins (poles) connect one to the WHITE (GND) and the other to

the FUNCTION pin… X,Y,X, GPIO0,GPIO1 or GPIO2 which is located on the inner portion of the PCB.

Documents

AtomCNC - Revision 1 · AtomCNC is a CNC Controller based on GRBL. It can control up to 4 axes in 2 different configurations, a XYZA type configuration where you have 4 separate axis