A lawnmower robot with GPS.

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This project attempts to create a lawnmower robot dedicated to trim the weed in the orchard, or any place where putting in wires to guide the robot is not feasible.

The robot is designed from scratch and has 3 areas of focus:
- The mechanical part of the robot
- The charging station (will be designed with solar panels in mind, for an off-grid setup)
- The guidance system for the robot, will attempt to optimize the battery usage by targeting the grass patches that haven't been cut, instead of driving randomly all other the place


The build instructions assume that you have basic experience with soldering, good knowledge of electronics, and Arduino programming. Also you'll need experience with RCs, have an RC Remote and receiver (at least in our prototyping phase). Also you need a 3D printer or a friend who has one.

You also have to be proficient with hand tools, electrical tools, be knowledgeable of safety when working with equipment that might harm you, your cat, your house or your neighbours. If you saw off your hand, blow the fuses in your house, drill holes in your kitchen counter, etc., it's all on you. 

The given list of components is mostly for reference. These are the components that either the author decided are best, had laying around, were easy to get, etc. You can decide on your own setup if you know what you're doing. But always check voltages, power ratings, amps draw, etc.

If you do start building this project, please DO NOT EXPECT HELP. It very much depends on the availability of the author, his mood, day of the month, phase of the moon, planets alignment and earth energy fields.

Build Phases

Building is done incrementally, by building a setup and testing parts of it before adding something else. For ex, first milestone is to make it remote controlled, and test the cutting performance, energy performance, drive system - the choice of motors, excessive vibrations, etc.

Only when I'm happy that so far it performs acceptably, I'll move on to making it autonomous by adding sensors, image processing with ESP32. In that phase I will check that the system is feasible - meaning it can cut down a area large enough, I'd be happy with 500-1000m2.

Third phase would be adding a charging station, correctly navigating to it and docking. 

Though it's on my mind making the system weatherproof, it will be done when everything else is working as expected

Design Notes

Motor Driver BTN-7960B

A note that I found on a website carrying this board:

To reach the high current, junction temperature must remain low. The BTN7960 module has small heat sink which is not enough to reach 10A to 43A range on a consistent manner. If you need continuos high current capability, better cooling technique (e.g. air flow, water cooling, etc) should be employed.

Note from myself:

Chinese are notorious for scrudging on thermal paste, remove the heatsink and check that enough has been applied!

Cutting Element

I went with a triblade for cutting bushes because.. well, just because it looked cool. I've seen people use paper cutter blades, and I definitely need to try that. Note: the cutter blades have 6mm hole, will design a mount for that.

NEED TO REDESIGN after latest test.

Vertical Motor

The big beefy motor is producing sparks, and I have no idea why (my basic knowledge of electronics doesn't stretch that far). Need to put the oscilloscope on the power lines to check if there aren't spikes introduced back into the system, that might affect arduino.

Standard Tesselated Geometry - 470.00 kB - 02/14/2020 at 18:23



Vertical Motor Mount

Standard Tesselated Geometry - 208.87 kB - 02/14/2020 at 18:23


View all 15 components

  • Blade mount test

    Radu Pascal02/19/2020 at 19:50 0 comments

    Re-printed the blade mount with 25% infill PETG and now I can spin it up at about 25% power without too much vibration. Beyond that, it starts vibrating and I don't want to risk another shuriken.

    P.S. the power consumption is between 3-4. I can't wait to get some grass to test it on!

  • I Built a Shuriken Shooting Machine!

    Radu Pascal02/18/2020 at 16:18 0 comments

    Today I managed to wire up the motor driving the blade, mount the blade on, get with my feet on a chair, and give it a go!

    What happened next was quite expected. I mean, expected when you prepare for failure. The blade started wobbling, I stopped the motor immediately, the blade detached from the motor, and flew away like a shuriken. Only to hit a cardboard box nearby. (Disclaimer: no cardboard boxes were harmed in this test).

    I mean.. I hoped the 3d printed blade to motor mount would good enough, but hope isn't equal with reality. That needs rethinking and probably redesigning.

    Next on the agenda, I noticed sparks in the motor:

    My [learn by googling knowledge of electronics doesn't stretch that far, and I need to figure out if this is critical or not..

  • First test!

    Radu Pascal02/16/2020 at 14:04 0 comments

    Of course these are not the best wheels to drive your robot indoors..

  • Wheels mounted!

    Radu Pascal02/14/2020 at 18:27 0 comments

    Mounted the wheels and motors:

View all 4 project logs

  • 1
    3d Print the parts

    The list of parts you need to print (don't forget to use filaments that are UV stable, I printed with PETG from Prusa). I used a Prusa MK3, a few notes on my settings - 5 bottom layers, 7 top layers, fan always on, 0.15 layer height on all components.

    2 Wheels - 20-25% infill should be enough

    2 Wheel motor mounts - if you don't find any metallic options. I bought my motors with mounts and I used those, but had the 3d mounts designed already.

    1 Vertical motor mount - use the most rigid filament you have, 15-20% infill

    Printed with Flexfill 98A:

    Cutter mount ( 2 part) - 20-25% infill

  • 2

    Get a plexiglass sheet of 4-5mm thick. Cut a piece of 40cm by 30 cm. (You can use whatever you have handy but will have to adjust the instructions for thickness) Try to cut it as square as possible.

    Use the 3D printed vertical motor mount to draw the template for cutting the hole to mount it.

    First decide on the placement of the cutting teeth, make sure they don't interfere with the front or rear wheels. When you'r happy with approximative placement, draw a line from left to right on the board, make sure it is perpendicular, and sketch and X at 15cm (given the width of the robot is 30cm). Place the motor mount with the flat side down , align the screw holes on the line, and draw the outlines of the circle that needs to be cut. 

    Use 3mm drill bits to drill holes around the perimeter, make sure to have enough clearing space. Also try to place them as close to each other as possible. Use 5-6 mm drill bits to enlarge the holes. 

    Use a Dremel with a cutting drill bit to cut the inner circle first:

    Enlarge and finish the circle to fit the vertical motor mount. Use two hands when holding the Dremel for better stability.

    Holding the mount tight, drill one hole for mounting using a 3mm bit, and then put a screw in and tighten it before drilling the rest of the holes:

    Also put a screw in the second hole and tighten it. Drill the rest of the holes.

    It's time to drill the holes for the swivel wheels and rear wheel motors.

    Use your best judgement. Try to space all of them as far away as possible from each other, but leave about 0.5-1cm of space from the border for the swivel wheels. The motor mounts should be flush with the side border.

    Plexiglass drilling tips:

    • if you are using plexiglass and need a large diameter hole, first drill a smaller one (half size) and then the bigger one.
    • drill with the smallest speed possible. When drilling fast it gets hot and starts to melt which blocks the drill. Use a electric screwdriver for that.
  • 3
    Swivel wheels

    Mount the swivel wheels. Use your best judgement. It all depends on what you find in stores. Mine are fixed with M6 screws:

    WARNING: don't tighten the screws too much, the metal part might not be perfectly flat, and will cause the plexi to bend and crack (that's what happened to me, but I noticed only the next day).

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