All Robots - Perimeter Wire Module

The perimeter wire transmitter sends the signal through the perimeter wire for the robot to detect the perimeter of the lawn.

The perimeter wire module works for both the Robot Mower and the Aerator, so only 1 module needs to be built to fence in both types of robot.


There are 2 build methods to create the perimeter wire transmitter

A. Perimeter Wire Module Using PCB build pack and WIFI

B. Perimeter wire Module using standard Arduino components 

Both methods will create a working perimeter wire transmitter.  The PCB version has the advantage of the circuits being completed by the PCB and it also includes a WIFI module so that the wire transmitter can be switched ON and OFF via the Blynk APP.

If you ordered a mower build pack all the components to make the standard wire module are included.

Instructions for the standard Arduino circuit are at the end of this page.



Build A:

Perimeter Wire Module Using PCB and WIFI

The following parts are included in the Wire Transmitter PCB Bundle.  If you ordered option 1 you will receive all the parts shown.  If you ordered option 2 you will receive the parts shown in the green box.




A 3D Printed Case for the PCB Perimeter Wire Transmitter can be printed.  The STL files are available here:

Perimeter Wire Transmitter


 The case and components are fixed with M3 screws (best black).


Step 1 - Build the BLYNK APP Wire ON/OFF Button.

The PCB version of the wire transmitter includes the ability to remotely turn the wire ON and OFF.

Go to the settings in your Mower APP and look for the devices settings


In the devices section add a new WeMos D1 (Wi-Fi) board.  Not the Auth Key which is sent to your account.  

Setup the following elements inside the Blank APP - Ensure they are linked to the new device WeMos D1 in the Source Box.


Segmented Switch - Pin V1

LED (Green) - Pin V2

LED (Red) - Pin V3



Step 2 - Upload the Code to the Boards

Before installing the Arduino Boards on the PCB first upload the code.

The software to upload to the Nano to create the wire signal and the WIFI code for the WeMoS D1 is available on the Arduino Downloads Page here: 

Ensure the WIFI settings are updated for your WIFI Network and that the Blynk APP Auth Code is updated in the Sender_Wemos sketch.



Step 3 - Install Header Pins

The female header pins are soldered in the following positions (in red).  this allows the easy removal of a component for whatever reason (damaged, defective etc). Cut the header pins to the right length to fit.

The header pins for the motor driver (6-9V and GND) are not standard spacing.  For this section 2 single header pins need to be cut out.

To ensure the header pins are straight its a good idea to use the components as jigs to hold the header pins as you solder them.

Step 4 - Prepare Components

Before installing the DC Step Down module ensure it is outputting approx 6.5V when a 12V input is applied.

Also stick the heat sink to the Motor Driver as shown.


Step 5 - Install Components (Except WIFI)

Install the components as shown.  DO NOT INSTALL THE WIFI MODULE UNDER POWER YET.  The WIFI module runs with 5V power and we first need to set a 5V source before installing it.  

Ensure the INPUT OUTPUT sides of the DC Step down module are correctly aligned.

Be Careful on the Arduino Nano.  Some Nanos have extra empty pins so ensure the correct pins are aligned.





Step 6 - Adjust Voltage

Ensure the switch is connected to the PCB otherwise the circuit wont work.  Now connect a 12V power supply to the PCB.  DO NOT INSTALL THE WIFI MODULE YET

You should measure 6.5V output from the DC Step Down.  If this is not 6.5V adjust using the adjustment screw on the DC step down module.

Now measure the voltage to the WIFI module at the 5V and GND pins.  By turning the screw on the variable resistor adjust the voltage to the WIFI module to 5V.


Step 7 - Install WIFI Module and re-adjust Voltage

Turn off the power and install the WIFI Module.  The WIFI module will add extra resistance to the circuit.  Re-measure the voltage on the WIFI 5V and GND pins.  Now carefully re-adjust the resistor screw to get 5V at the WIFI module. 

If the WIFI module receives less than 5V it wont turn on.




Step 8 - Test and Install Perimeter Wire

The perimeter transmitter should connect to your WIFI network and via the Blynk APP you should be able to turn the module ON and OFF.  The LED's on the Blank APP confirm that the signal has been received by the WIFI module and should change accordingly.

The Perimeter wire cable can now be attached the to the plug as shown.


Auto Wire ON/OFF.

Version V9.5 of the software has an automatic wire ON/OFF feature.  Copy the Blynk Auth key from the WEMOSD1 Blynk APP into the NodeMCU Arduino Sketch.  This gives the NODEMCU access to the PCB Wire WEMOS D1 board and can automatically turn ON and OFF the wire depending on the mower status



Video of finished  Wire Transmitter (PCB Version)







Build B:

Perimeter wire Module using standard components.

All the components to complete the standard perimeter wire transmitter are including in the mower build packs.

The software to upload to the UNO to create the wire signal is available on the Arduino Downloads Page here: 


The components are connected as shown below.

To turn the motor driver from a double bridge (2 Motors) to a single bridge (i.e. combine the power of both drivers) the motor driver can be bridged like this.



Out1 -> Out4 /   Out2 -> Out 3  /   IN1 -> IN4   /   IN2 -> IN3 

This will give more power to the perimeter fence wire.



A 3D Printed Case for the Perimeter Wire Transmitter can be printed.  The STL files are available here:

Perimeter Wire Transmitter Case (no PCB).zip

The case and components are fixed with M3 screws (best black).











Testing the Wire Signal

When testing the circuit a long length of wire is required (min 20 meters) otherwise the resistance will be too small for the module to work.  I use 3mm diameter, metal stranded, plastic coated wire for the perimeter wire which is available here 






See the Main menu for further instructions