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Maker Shield – Uno Compatible Shield

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Table of Contents

Introduction

The Maker Shield is an all in one GRBL 1.1 compatible stepper motor shield designed for the Arduino Uno and Uno compatible microcontroller boards. It has been designed to be easy and intuitive to use with no requirement for additional driver modules.

 

Key Features

  • Reverse polarity protection for the main motor power input (VMOT)
  • Onboard Texas Instruments DRV8825PWPR stepper motor driver IC’s
  • Dupont motor header pins (A1, A2, B2, B1) for each drive channel
  • Onboard Micro Step (up to 1/32) and drive channel enable dip switches
  • LED error indicators for each drive channel (including the CLONE channel)
  • LED driver Enable indicator
  • Voltage Reference pad for easy current adjustment of each drive channel
  • Two VMOT header pins (dependant on input voltage used and a Maximum of +24V)
    • VMOT Header pins can be used for a cooling fan
  • X-Axis, Y-Axis, and Z-Axis header pins for the Clone Axis drive channel
  • X, Y and Z channel Limit switch inputs with Loop header pin
    • The loop header pins allows for a connection of up to two limit switches per drive channel directly to the board. (when used as a Normally Closed loop)
  • Additional GRBL header pins include,
    • Probe Pin – Allowing you to set the correct height of your milling tool
    • Cool Pin – Coolant control
    • Resume – Continue GRBL job after a Hold command or door open (if configured within grbl)
    • Hold – Pause the current GRBL job
    • Abort – GRBL reset function
    • Reset – Full Arduino Uno board reset
    • PWM – GRBL PWM output for milling or laser cutters that support variable speed / power
    • Spin Dir – GRBL Spindle Enable pin when configured as a milling machine
  • Handy micro step table on the back of the Maker Shield

For GRBLv1.1 configuration settings, refer to https://github.com/gnea/grbl/wiki/Grbl-v1.1-Configuration

Application

The Maker Shield CNC Controller is suitable for a variety of small and medium sized automation equipment and instruments including but not limited to: CNC machines, laser engraver / cutter, plotters and drawbots. The integrated drivers are capable of driving standard 4 wire stepper motors with up to 2.5 Amp drive capability per motor coil.
 

Detailed Pin Descriptions

This section will describe the connection and adjustment settings to get the best out of your Maker Shield. It is recommended to read through this section to become familiar with this board. 

Stepper Motor Output Header Pins

The stepper motor header pins are a 4- way Dupont style header pin that describes which drive channel it is used for and the relevant pin assignments. To ensure you get correct motor functionality and rotational direction, refer to your stepper motor wiring guide. Note: The Maker Shield pin assignments are a guide only and while the current assignments are marked as B1 B2 A2 A1 these can also be transcribed as B+ B- A- A+.

Microstep and Enable DIP Switch

Each motor drive channel comes with its own Microstep and channel Enable DIP switch (Z Axis channel shown in picture). To set the required microstep resolution refer to the table below or the table on the back of the Maker Shield. Important NOTE: Ensure you refer to the numbers marked on the board (Circled in RED in the image to the right below) for correct micro step settings and not the numbers marked on the switch itself.

Note : It is important to note that if a drive channel is not being used (not connected to a motor) that the relevant EN switch is in the ‘Off’ position.

Driver Enable Indicator

The Maker Shield incorporates a green GRBL Enable indicator as a visual reminder that the driver IC’s are energised and supplying power to the connected stepper motors.

Drive Channel Error Indicator

Each drive channel incorporates its own error indicator (Y drive channel shown in image) that will illuminate if there is a problem with the driver IC. Some error conditions are overheating or over current detection. If an error condition is detected and is persistent check all wiring is correct and connectors are firmly seated.

Voltage Reference Adjustment

The voltage reference adjustment allows for setting the current output (up to approximately 2.4 Amp) of the driver channel IC. It is important to ensure that the output current matches the motor current rating to ensure smooth and correct operation of your stepper motor. If the values are incorrect, you may end up overheating your motors if the current is set too high or under-powering your motors if the current is set too low. This board also incorporates a handy voltage reference pad for each drive channel.

Limit Switch Connector

The limit switch connector allows up to two limit switches per channel to be directly connected to the Maker Shield. This is achieved by the Loop connector for the respective channel input.

Clone Axis Header Pins

The Clone axis header pins allow you to clone either the X, Y or Z driver channel. When you are cloning an axis, select the step and direction pins for that particular axis that you would like to clone. For more information on how to clone an axis, refer to the Component Assembly section of this manual on how to clone an axis.

Driver IC Cooling

It is highly recommended to provide adequate cooling (heatsinks and fan) for the driver IC’s during normal operation. These drivers can get hot enough to burn before they will shut down due to overheating and will not resume normal operation until the appropriate temperature threshold has been reached. Allowing the motor drivers to overheat may result in missed steps or poor performance. It is recommended to use the provided adhesive heatsinks to aid in heat dissipation. 

VMOT Header Pins

The VMOT header pins provide an additional power output that is tied to the VIN voltage used to drive the stepper motors (Max 24V). These pins can be used to run a cooling fan to ensure better cooling and more efficient operation of your Maker Shield.

GRBL Input and Output Header Pins

This board utilises the standard 2.54mm Dupont style header pins (as described in Section 2) for easy and convenient connection of external accessories. Ensure that the polarity of the header pins is correct before connecting peripherals.

Reset Button

The onboard reset button will perform a reset of the Arduino Uno compatible controller. Pressing this button during operation will cause you to lose the current workload that is running on your Arduino Uno compatible controller and halt the current operations. This reset button performs the same function as the Arduino Uno compatible controller’s onboard reset button.

Motor Power Input Connector

The motor power input connector (Blue) is located on the left-hand side of the board. This is where the main power from your power supply is fed into the Maker Shield. Note the polarity marked on the board. Make sure that the maximum input voltage is 24V.

Assembly

Arduino and Maker Shield connection

While taking normal static electricity precautions, insert the Maker Shield onto the Arduino Uno, making sure that the Maker Shield pins are correctly aligned with the Arduino’s pins. Take care not to bend the pins.

Limit Switch Wiring

Limit switches are necessary if you intend to home your machine and prevent your machine from running into the end of the gantry. We recommend using our 2 Core Shielded Cable to eliminate any potential noise.

There are 2 methods of wiring your limit switches; Normally Closed and Normally Open. The standard configuration in GRBL is the Normally Open configuration. If you wish to use the Normally Closed configuration, you will need to invert the settings in the GRBL settings by changing the $5 setting from 0 to 1.

As shown above our limit switches have 3 pins;

  • Pin 1: Common
  • Pin 2: Normally Closed
  • Pin 3: Normally Open

Normally Open Configuration: If you are using our 2 core shielded cable, connect the blue wire to the “Common” (Pin 1) and the white wire to “Normally Open” (Pin 3).

Normally Closed Configuration: If you wish to use the Normally Closed configuration in your build, connect the blue wire to the “Common” (Pin 1) and the white wire to “Normally Open” (Pin 2).

Method 1: Standard Normally open Limit switch Configuration.

Note that the images below are for illustrative purposes. The signal wire colour in this manual is yellow, use white colour instead as included in your kit.

See the wiring for the Normally Open configuration in the diagram below. This example is for the X axis limit switch. Repeat this step for the Y and Z axis limit switches.

Method 2: Loop configuration with 6 limit switches.

This method shows the connection for wiring two limit switches, this configuration requires the normally closed configuration. Repeat this step for the Y and Z axis limit switches.

Emergency Stop Switch Wiring

Emergency stop switches are recommended for stopping your machine in case of an emergency. When activated, this will cut power to the controller and all work/machine position will be lost.

Cloning the Y-Axis

If your machine has a mirrored axis, also known as a slave axis, the axis will need to be cloned. In most cases the machines have a dual Y-Axis. See below on how to clone the Y-Axis. Insert a shunt in the YD and YS headers as indicated below:

Stepper Motor Wiring

It is important to ensure that your motors are wired correctly. Bipolar stepper motors have 2 coil pairs within them and therefore the wiring has to match these coils The coils typically have a labelling system that labels these coils, A+, A-, B+, B-. A+ and A- correspond to the first coil and B+ and B- correspond to the second coil. In the example shown below for the Nema17 motor; green and black make up coil A and blue and red make up coil B. If these coils are mixed, the motors will vibrate instead of turn or turn in one direction only. For our Nema23 stepper motors, the wiring sequence is Red, Green, Blue , Yellow, for A+, A-, B+ and B- respectively.

Power Supply Wiring

For the best performance, it is recommended to use the MeanWell 350W 24V power supply. Do not exceed the recommended supply voltage of 24V as damage to the components may occur. Ensure that V+ from the Power Supply is connected to V+ on the Maker Shield (red wire) and V- from the power supply to V- of the Maker Shield (Black wire. Our cable has white wire. The Black has been used for illustrative purposes.).

Stepper Motor Driver Settings

To get the best performance from your motor, it is recommended to tune your current and micro-step settings. See below for the settings. 

Enabling your motors

As mentioned earlier, the SW1 on your control board corresponds to the enable pin for that particular axis. If you wish to use that axis, enable the axis by moving the dip switch to the UP position. The motor enable interface is shown below:

Current Settings

As stepper motors are current driven devices, you will need to finetune your current settings. Refer to the table below for tuning the current. Refer to the datasheet of your stepper motor to get the correct current rating.

Reference Voltage (V) Driver current Output (A)
0.1 0.2
0.2 0.4
0.3 0.6
0.4 0.8
0.5 1.0
0.6 1.2
0.7 1.4
0.8 1.6
0.9 1.8
1.0 2.0
1.1 2.2
1.2 2.4

To set the current for the driver, you will need the following:

  • A multimeter set to measure DC voltage
  • A small Phillips head screwdriver
  • 2 ended alligator clip.

Procedure:

Refer to the diagram below while you are following the steps.

  • Turn on your Maker Shield
  • Turn on your multimeter to read DC Voltage
  • Attach one end of the alligator clip to the screwdriver and the other end to the positive probe of your multimeter.
  • Attach the negative probe to the Voltage reference pad named REF highlighted with the Red square and insert the screwdriver in the adjustment potentiometer. Note that each driver has its own reference pad with the axis label next to it. There is also an adjustment potentiometer specific to the driver. For example, the Y axis Voltage reference pad is named REFY with the potentiometer just below the driver highlighted by the Green square.
  • Adjust the Vref to suit your motor. The Vref is 50% the current value. For example, if your motor is 1.0A, adjust the Vref to be 0.5V
  • Repeat this for each axis that you intend to use in your build

Micro-Step settings

Apart from current settings, stepper motors can be further fine tuned by means of setting the micro steps. Increasing the micro-steps increases your accuracy. The recommended micro step setting is 1/8th step. The table below will show you how to set the micro-step rate.

IMPORTANT NOTE: Follow the micro step numbering on the silkscreen on the board highlighted in the Green square not the dip switch itself as SW1 corresponds to the Enable pin for the relevant motor.

Micro Stepping Rates

Micro-Step SW1 SW2 SW3
FULL OFF OFF OFF
1/2 ON OFF OFF
1/4 ON ON OFF
1/8 ON ON OFF
1/16 OFF OFF ON
1/32 ON ON ON

To set the micro step, peel off the orange protective film on the dip switches and set the dip switch to the desired setting. Flipping the dip switch upwards puts it in the ON position. Note that you may need to adjust the micro-stepping rate in the software as well, depending on the gcode sender that you are using. This guide uses 1/8th step so no further calculations are required as to the steps per revolution settings in GRBL.