Friendly Robotics RL850/RL1000 rebuild

  • Project Goal & Requirements

The main aim is to replace the control electronics of a Friendly Robotics RL850/RL1000 lawnmower.

  • The software and control electronics will be open-source, and modularised so that it will be easy to port to other platforms
  • The bot must use power efficiently. It should mow the lawn intelligently, avoiding areas that are already mown. It should use the minimum amount of power necessary to mow the lawn (throttling back blade speed when areas only need to be lightly mown, shutting down the mowing motors when over unmowable areas)
  • The bot must support scheduled mowing
  • The bot must not mow the lawn if it is currently raining, or has rained recently
  • The bot must be able to communicate with computers/phones to set parameters, check status, etc

Current Status



IO Board Requirements

The IO board will allow the PC to interface with the bot motors and sensors. Where possible, the components will be salvaged from the original motherboard. It can be powered from a standard molex connector from the ATX PSU.

The following components can be salvaged:

Usage Digital Out Digital In PWM Analog In
Drive Motor Left     4 1
Drive Motor Right     4 1
Cutting Motor 1     1 1
Cutting Motor 2     1 1
Cutting Motor 3     1 1
Warning Light 1      
Battery Current Monitor       1
Battery Voltage Monitor       1
Front Bump Sensor   1    
Rear Bump Sensor   1    
Front Wheel Sensor   1    
Wire Sensors       4
Accelerometer       3
Digital Compass ??? 5
Alarm 1      

 Totals 7 3


So from the table above, it all fits (just) within the capabilities of the Arduino Mega, which has 14 PWM lines and 15 analog inputs.

IO Board Power

The IO board will take in the mains (+24V) from the battery, and pass it on to the ATX PSU for regulation. The PSU will feed power back to the IO board via a standard Molex PC connector.

As the chargers open circuit voltage is +40V, and the maximum input voltage of the ATX PSU is 28V, we will need to clamp the power supply input voltage to 24V.



  • Complete features & requirements
  • Design IO board
  • Write hardware abstraction layer
  • Test hardware abstraction layer
  • Write basic functionality (implement original algorithms for scanning yard without positioning information)
  • Test basic functionality
  • Write advanced functionality