Add Bluetooth to Your Plotter

This instructable explains how to replace your USB plotter cable with a bluetooth wireless link.

Your plotter [1] may now be placed in a convenient location that is remote from your computer.

This add-on module is compatible with any arduino circuit that uses a serial connection ... no coding is required.

[1]

The following plotters are USB only and would benefit from bluetooth:

• https://www.instructables.com/id/CoreXY-CNC-Plotte...
• https://www.instructables.com/id/CNC-Drawing-Arm/
• https://www.instructables.com/id/CNC-Dual-Arm-Plot...
• https://www.instructables.com/id/CNC-Dual-Arm-Plot...

The circuit comprises two resistors, an HC-06 bluetooth module, and an arduino UNO R3 microcontroller.

The bluetooth module, and the arduino, both treat voltage levels greater than 2 volts as a logic HIGH, and voltages less than 0.8 volts as a logic LOW.

Resistors R1 and R2 reduce the 5 volt TTL output voltage from the arduino to 3.2 volts to prevent damage [1] to the CMOS chip in the HC-06 bluetooth module.

Removing the USB cable also removes the 5 volt power to the arduino. Power to the arduino is restored by connecting a wire from the external 12 volt stepper-motor supply and the Vin pin on the arduino.

Use a 4-pin socket when wiring the bluetooth module as the HC-06 MUST be removed [2] whenever you attempt to program the arduino ... you can't have two serial ports active at the same time.

[1]

Because the HC-06 uses 3.3 volt CMOS technology all input voltages must be less than 3.6 volts ... preferably around 3.3 volts. The maximum voltage at the HC-06 RXD input is therefore:

5*R2/(R1+R2) = 5*2700/(1500+2700) = 3.214 volts

[2]

When programming your arduino:

• Switch off the plotter
• Remove the HC-06 bluetooth module
• Connect a USB cable from your computer to your arduino

When using bluetooth:

• Remove the USB cable from the arduino
• Insert the HC-06 bluetooth module into its socket
• Switch on the plotter

The parts are listed in photo 1

Any socket with 2.54mm pin spacing may be used.

An additional jumper wire is required for applying power to the Vin pin of the arduino.

I obtained my HC-06 bluetooth module from https://www.aliexpress.com/

Step 1

• Remove the pin from one end of each jumper and solder the components as shown in photo1. The order is not critcal ... whatever is easiest when soldering.
• Ensure that the 1500 ohm resistor is connected to the orange wire.

Step 2

• Remove the break-off support bar holding the socket-pins and slide them into the socket housing.
• Ensure that the pins are inserted in the order shown in photo 2.

Step 3

• Reinforce the leads using a piece of construction tape.
• Each lead in photo 3 is labelled with the arduino socket into which it must be placed.

Step 4

• Photo 4 show the bluetooth module fitted to the coreXY plotter described in instructable https://www.instructables.com/id/CoreXY-CNC-Plotte...

The following steps assume the arduino serial port is configured for 9600 bauds.

Step 1

• Switch off the 12 volt supply to the plotter.
• Remove the USB cable from your computer.

Step 2

• Remove the HC-06 bluetooth module from its socket.
• Insert the four bluetooth leads into your arduino.
• Connect a jumper wire between the external 12 volt plotter supply and the arduino Vin socket.

Step 3

• Turn on the 12 volt supply. Your arduino should boot normally.
• Measure the voltage between the resistor junction and ground. It should measure around 3.2 volts.

Step 4

• Switch off the 12 volts.
• Insert the HC-06 bluetooth module into its socket.
• Check that the bluetooth module is correctly orientated.

Step 5

• Switch on the 12 volts. The LED on the bluetooth module should start flashing.

This completes the installation and testing ... we now need to "pair" the HC-06 bluetooth module with your computer.

Before your computer can talk to the HC-06 bluetooth module it needs to know all about it. This process is called "pairing".

Once "paired" the name of the bluetooth module will appear in a list of bluetooth devices that the computer can talk to.

The following steps assume that a Windows 10 computer is being used:

Step 1

• Switch on your plotter ... a LED on the HC-06 will start to flash.
• Left-click the Start window and select Settings.
• Left-click Devices (photo 1) in the window that appears.

Step 2

• Ensure that Bluetooth is ON in the "Bluetooth &other devices" window (photo 2).
• Left-click "Add Bluetooth or other device".

Step 3

• Left-click "Bluetooth" in the "Add a device" window (photo 3).

Step 4

• Left-click "HC-06" from the window that appears (photo 4).

Step 5

• Enter "1234" (without the quotes) when asked for a password (photo 5) and a "paired" message will appear (photo 6).

Step 7

Check that the HC-06 appears in the list of paired devices lower down the page (photo 7).

Step8

• Exit the settings menu.

Communication with your plotter requires a software "Terminal".

A suitable gcode terminal is described in instructable https://www.instructables.com/id/CNC-Gcode-Sender/.

Step 1

• Download and install this software ... full instructions are included.

Step 2

• Click the top-left "Run" button.
• The LED on the HC-06 bluetooth module will stop flashing when a link is established.
• A menu similar to that in photo 1 will appear if you are using the plotter described in instructable https://www.instructables.com/id/CoreXY-CNC-Plotte...

Happy plotting ...

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