An autonomous roving CNC weeding/cultivating machine guided by GPS and coloured markers.

Similar projects worth following
Two years ago I initiated the Weedinator Project to fight back against the onslaught of weeds which threatened to dominate the leeks that I was growing. In the meantime, the weeds seem to have adapted to my mechanised approach and the war is far from over.

I am now ready to take the fight to a higher level with an autonomous GPS/Objects guided roving CNC machine that will destroy every living organism (except for the leeks) on the surface of the earth with powerful 25Kw butane fuelled flame throwers with localised temperatures of over 1200 degrees C.

Last year's efforts resulted in a tractor mounted weeding machine which worked reasonably well except for the fact that it was not accurate enough and sometimes ended up destroying the leeks as well as the weeds. The video below shows the results:

Since then I have been exploring CNC, GPS and GPRS technology and feel 97.2% confident that I can create a roving weeding machine that can also perform other tasks such as cultivating (digging) and mowing with the right attachments. Think 'Moon buggy' or the 'Mars Rover' and that will be what I'm aiming for. Actually, there is already an open source project for the CNC part - the Farm Bot.

The machine will carry it's own electric generator running on gas/diesel and be propelled forwards/backwards/sideways with stepper motors/servos. Coloured markers, detected by an object recognition system, will be placed in the soil to create grids for the Weedinator to work within as GPS is not accurate to the scale of 1 mm which will be necessary to avoid killing the crops. GPS will be used to navigate to particular fields or seed beds.

As time goes on a more intelligent object recognition system will be incorporated to detect individual weeds:

The flame thrower will be mounted on a normal CNC frame with 3 axis of movement and the nozzle itself will be shrouded by metal sheet to prevent damage to the crops themselves. Individual weeds could be zapped by a small gas powered butane torch as used by a chef when making crème brulee.

This may seem like a very ambitious project, but the actual chances of achieving success are quite high. Much of it depends on the quality of the code written for reading the GPS data and transforming that into real-time steering and motion. It all just seems like great fun to me!

Programming new coordinates into the Weedinator via the cell phone network is not going to be difficult as much of the task of handling GPRS data has already been covered in my weather station project.

There is a risk that as the project evolves we will run out of programming space or computing power on the MCU ...... So ....... Just add another one and get them talking to each other via the I2C bus, which I also had up and running on the weather station project, although my code for this communication does now seem a little bit 'clunky'.

The greatest 'risk' is due to the cost involved in buying all the components - the GPS system is expensive and it currently requires 12 stepper motors just for the steering, suspension and wheel drives. Each stepper motor needs it's own controller which, although homemade, are still a bit pricey. When I say risk, I'm really referring to 'How useful is this thing actually going to be when it's finished?' Yes, there's a very good chance that we can build it and it will work, but how well will it work? For example, it might be incredibly slow.

Current overall chances of success = 85%.

Components list 01.xlsx

Electronic components

sheet - 11.12 kB - 08/28/2017 at 09:07


weedinator 01.wav

The next Weedinator video is going to need a sound track. Here's a snapshot of what it might comprise.

Waveform Audio File Format (WAV) - 8.93 MB - 05/20/2017 at 09:45


Adobe Portable Document Format - 1.59 MB - 05/07/2017 at 13:01


Adobe Portable Document Format - 1.23 MB - 05/07/2017 at 13:01


Adobe Portable Document Format - 1.35 MB - 05/07/2017 at 13:01


View all 14 files

  • Photos of the Old Tractor Mounted Weedinator

    TegwynTwmffat08/31/2017 at 16:09 0 comments

  • Side view of Mechanism

    TegwynTwmffat08/28/2017 at 09:09 0 comments

  • New Stepper Motor PCB ready for Fabrication

    TegwynTwmffat08/09/2017 at 17:15 0 comments

    Having given up on the STM L6482H stepper driver chip, for lack of software, the TI DRV8711 has now been laid out in PCB design software with it's associated MOSFETS. The design features attachment holes for two large aluminium heat sinks and a small 12 volt fan.

    Each of these boards has it's own Nano MCU which can be programmed for acceleration and torque characteristics and each motor has it's own board resulting in semi-autonomous motors. The boards will be stacked vertically on another PCB and individually controlled by a Master MCU via the I2C bus. Sounds complicated? Will this machine really have over 12 MCUs in it? ...... All will be made clear in future updates!

  • Artist's Impression of the Weedinator

    TegwynTwmffat08/04/2017 at 08:40 0 comments

  • Testing Weedinator Suspension Stepper Motor Driver

    TegwynTwmffat07/20/2017 at 17:08 0 comments

    The Weedinator uses a novel stepper motor driven system for it's 'suspension':

    I've deliberately avoided the normal spring type suspension as the machine must not wobble about when the cultivating / weeding mechanism is working and the overall machine needs to be effectively 'rigid' in relation to the ground, although there will be some 'give' in the tyres.

    The technical name for the motor is 'Non Captive Stepper Motor' and the one I'm using is a Nema 34 with a rated linear holding torque of 3500 N, so it was on planet earth and operating in parallel with the earth's core, it would hold still a massive 350 kg!

    In the test I set the motor to 16 steps and maximum torque using an Arduino Mega and put about 500 N force on the motor BEFORE turning it on. As can be seen in the video below, the motor accelerated up to speed and moved up the spindle reasonably quickly:

  • Weedinator Transmission Mechanism

    TegwynTwmffat07/16/2017 at 12:00 0 comments

    During the design process, initially there is rapid progress and the design changes very noticeably. As time goes on the rate of change decreases and there comes a point where it's ok to actually build the mechanism.

    Using 3D software such as Fusion 360, we can model the mechanism with incredible ease and view it as an animation to check that components mesh with each other properly and don't bump into each other either. I think that currently the design is at about 95% 'finished' and I aim to create the first prototype at 98%, so there's a bit more work to go in Fusion 360:

  • Testing Texas Instruments DRV8711 with Nema 34 Stepper Motor

    TegwynTwmffat07/15/2017 at 15:27 0 comments

    I was not having much success with the STM 6482 due to lack of good software examples so switched to the DRV8711 chip which has a few less functions, but much easier to get up and running. There's no SPI acceleration / deceleration control, but managed to write this into code fairly easily using the good old 'millis and previous millis' trick:

      digitalWrite (DIRpin, dir) ;
      unsigned long currentMillis = millis();
        if (currentMillis - previousMillis >= interval) 
        previousMillis = currentMillis;

    The Tone library gives really nice smooth motor operation and I can gently ramp up the speed and torque quite nicely, preventing sudden current inrush.

    Next job is to create a PCB for each of the 12 motors. The current idea is to stick an Arduino Nano on each PCB and link all the PCBs together via the I2C bus - this seems to be the only way to get good simultaneous control of all 12 of them! Hopefully, most of the acceleration and torque profiles can just be uploaded onto the Nanos and then (mostly) forgotten about.

    The image above also shows the gearboxes, which currently are being selected as 100:1. Sometime soon I'll be able to actually build one of the wheel/steering/suspension modules.

  • Direct drive

    TegwynTwmffat07/15/2017 at 14:08 0 comments

    I managed to get rid of all the belts and pulley wheels by using direct drive through the gearbox.

  • Setting up STM 6482 stepper motor driver chip

    TegwynTwmffat07/09/2017 at 13:46 0 comments

    I really thought that this was going to be relatively easy, but soon a bit of a nightmare started to unfold.

    Since we've got quite a few motors running at the same time, doing various different jobs, we want really good control options so that means using the SPI bus with one MCU pin to shift the registers on each motor PCB. Speed, acceleration, torgue, current sensing has to be done via SPI and not PWM or else we'd soon run out of MCU pins. The STM 6482 seems to be the best chip for the job, but it's quite complicated to set up.

    After buying the STM 6482 discovery board and playing around on it with a swanky GUI I managed to convince myself that it would be ok. Next stage was to try and get the STM Eval board up and running.

    First problem: No software available! Fortunately, after emailing STM, they fixed the broken download link and now I've got a shed load of files to compile into a working system.

    Next problem: After literally an hour of arranging the files in the Mbed software the compiler throws out an error: 'Please select your Nucleo board' ...... Very polite but it turns out that the software only supports a narrow range of nucleo boards and my F072Rb aint one of them! Eventually I work out that I need a STMF103RB with 128k of flask to be defined in the software as 'Medium Density, Non Value Line'. Fortunately the boards are not expensive and they're in stock at RS supllies. Meanwhile, my test rig awaits patiently:

    The 'build' for the compilation looks quite well documented:

    @page cSPIN_Example cSPIN

    * @file cspin/readme.txt
    * @author IPC Rennes
    * @version V2.1
    * @date November 4, 2013
    * @brief Description of the cSPIN Example.
    * @note (C) COPYRIGHT 2013 STMicroelectronics
    * @copy
    * <h2><center>&copy; COPYRIGHT 2013 STMicroelectronics</center></h2>

    @par Example Description

    This example shows how to use cSPIN firmware library. Main program starts with
    clock configuration (system clock config SYSCLK to 24MHz).
    The SYSCLK frequency is selected by user in clock.h file.

    All used peripherals are then initialized, cSPIN chip is configured (registers are
    set with requested parameters).

    Different commands are then shown to perform requested operation.

    @par Directory contents

    - cspin/inc/stm32f10x_conf.h Library Configuration file
    - cspin/src/stm32f10x_it.c Interrupt handlers
    - cspin/inc/stm32f10x_it.h Header for stm32f10x_it.c
    - cspin/inc/clock.h System clock setup related header
    - cspin/src/clock.c System clock source file
    - cspin/inc/cspin.h cSPIN definitions header
    - cspin/src/cspin.c cSPIN routines source file
    - cspin/inc/cspin_config.h cSPIN configuration parameters (this file can be generated by the GUI)
    - cspin/inc/main.h Main header file
    - cspin/src/main.c Main program
    - cspin/src/pre_include.h First header file included by the preprocessor

    @par Hardware and Software environment

    - This example has been tested with :
    EVAL6480H-DISC board
    EVAL6482H-DISC board.

    @par How to use it ?

    In order to make the program work, you must do the following :
    - Create a project and setup all project configuration
    - For the DISCOVERY board :
    - Device : ST STM32F105xB
    - Library low-level interface: Semihosted. stdout/stderr Via SWO. Use CMSIS library
    - Preprocessor defined symbols :
    - STM32F10X_CL

    Read more »

  • Stepper motors with gearboxes allow nice slow, controlled movement

    TegwynTwmffat06/08/2017 at 18:47 0 comments

    The wheel modules start to take shape. Stepper motors with gearboxes allow nice slow, controlled movement with the option to apply electric brakes to stabilise the machine when it is doing actual weeding / cultivating, otherwise it would move around slightly due to inertial forces acted by the cultivating equipment.

View all 20 project logs

  • 1


    Creative Commons Attribution-ShareAlike 4.0 International Public License

    By exercising the Licensed Rights (defined below), You accept and agree to be bound by the terms and conditions of this Creative Commons Attribution-ShareAlike 4.0 International Public License ("Public License"). To the extent this Public License may be interpreted as a contract, You are granted the Licensed Rights in consideration of Your acceptance of these terms and conditions, and the Licensor grants You such rights in consideration of benefits the Licensor receives from making the Licensed Material available under these terms and conditions.

    Section 1 – Definitions.

    1. Adapted Material means material subject to Copyright and Similar Rights that is derived from or based upon the Licensed Material and in which the Licensed Material is translated, altered, arranged, transformed, or otherwise modified in a manner requiring permission under the Copyright and Similar Rights held by the Licensor. For purposes of this Public License, where the Licensed Material is a musical work, performance, or sound recording, Adapted Material is always produced where the Licensed Material is synched in timed relation with a moving image.
    2. Adapter's License means the license You apply to Your Copyright and Similar Rights in Your contributions to Adapted Material in accordance with the terms and conditions of this Public License.
    3. BY-SA Compatible License means a license listed at, approved by Creative Commons as essentially the equivalent of this Public License.
    4. Copyright and Similar Rights means copyright and/or similar rights closely related to copyright including, without limitation, performance, broadcast, sound recording, and Sui Generis Database Rights, without regard to how the rights are labeled or categorized. For purposes of this Public License, the rights specified in Section 2(b)(1)-(2) are not Copyright and Similar Rights.
    5. Effective Technological Measures means those measures that, in the absence of proper authority, may not be circumvented under laws fulfilling obligations under Article 11 of the WIPO Copyright Treaty adopted on December 20, 1996, and/or similar international agreements.
    6. Exceptions and Limitations means fair use, fair dealing, and/or any other exception or limitation to Copyright and Similar Rights that applies to Your use of the Licensed Material.
    7. License Elements means the license attributes listed in the name of a Creative Commons Public License. The License Elements of this Public License are Attribution and ShareAlike.
    8. Licensed Material means the artistic or literary work, database, or other material to which the Licensor applied this Public License.
    9. Licensed Rights means the rights granted to You subject to the terms and conditions of this Public License, which are limited to all Copyright and Similar Rights that apply to Your use of the Licensed Material and that the Licensor has authority to license.
    10. Licensor means the individual(s) or entity(ies) granting rights under this Public License.
    11. Share means to provide material to the public by any means or process that requires permission under the Licensed Rights, such as reproduction, public display, public performance, distribution, dissemination, communication, or importation, and to make material available to the public including in ways that members of the public may access the material from a place and at a time individually chosen by them.
    12. Sui Generis Database Rights means rights other than copyright resulting from Directive 96/9/EC of the European Parliament and of the Council of 11 March 1996 on the legal protection of databases, as amended and/or succeeded, as well as other essentially equivalent rights anywhere in the world.
    13. You means the individual or entity exercising the Licensed Rights under this Public License. Your has a corresponding meaning.

    Section 2 – Scope.

    1. License grant.
      1. Subject to the terms and conditions of this Public License, the Licensor hereby grants You a worldwide, royalty-free, non-sublicensable, non-exclusive, irrevocable license to exercise the Licensed Rights in the Licensed Material to:
        1. reproduce and Share the Licensed Material, in whole or in part; and
        2. produce, reproduce, and Share Adapted Material.
      2. Exceptions and Limitations. For the avoidance of doubt, where Exceptions and Limitations apply to Your use, this Public License does not apply, and You do not need to comply with its terms and conditions.
      3. Term. The term of this Public License is specified in Section 6(a).
      4. Media and formats; technical modifications allowed. The Licensor authorizes You to exercise the Licensed Rights in all media and formats whether now known or hereafter created, and to make technical modifications necessary to do so. The Licensor waives and/or agrees not to assert any right or authority to forbid You from making technical modifications necessary to exercise the Licensed Rights, including technical modifications necessary to circumvent Effective Technological Measures. For purposes of this Public License, simply making modifications authorized by this Section 2(a)(4) never produces Adapted Material.
      5. Downstream recipients.
        1. Offer from the Licensor – Licensed Material. Every recipient of the Licensed Material automatically receives an offer from the Licensor to exercise the Licensed Rights under the terms and conditions of this Public License.
        2. Additional offer from the Licensor – Adapted Material. Every recipient of Adapted Material from You automatically receives an offer from the Licensor to exercise the Licensed Rights in the Adapted Material under the conditions of the Adapter’s License You apply.
        3. No downstream restrictions. You may not offer or impose any additional or different terms or conditions on, or apply any Effective Technological Measures to, the Licensed Material if doing so restricts exercise of the Licensed Rights by any recipient of the Licensed Material.
      6. No endorsement. Nothing in this Public License constitutes or may be construed as permission to assert or imply that You are, or that Your use of the Licensed Material is, connected with, or sponsored, endorsed, or granted official status by, the Licensor or others designated to receive attribution as provided in Section 3(a)(1)(A)(i).
    2. Other rights.
      1. Moral rights, such as the right of integrity, are not licensed under this Public License, nor are publicity, privacy, and/or other similar personality rights; however, to the extent possible, the Licensor waives and/or agrees not to assert any such rights held by the Licensor to the limited extent necessary to allow You to exercise the Licensed Rights, but not otherwise.
      2. Patent and trademark rights are not licensed under this Public License.
      3. To the extent possible, the Licensor waives any right to collect royalties from You for the exercise of the Licensed Rights, whether directly or through a collecting society under any voluntary or waivable statutory or compulsory licensing scheme. In all other cases the Licensor expressly reserves any right to collect such royalties.

    Section 3 – License Conditions.

    Your exercise of the Licensed Rights is expressly made subject to the following conditions.

    1. Attribution.
      1. If You Share the Licensed Material (including in modified form), You must:
        1. retain the following if it is supplied by the Licensor with the Licensed Material:
          1. identification of the creator(s) of the Licensed Material and any others designated to receive attribution, in any reasonable manner requested by the Licensor (including by pseudonym if designated);
          2. a copyright notice;
          3. a notice that refers to this Public License;
          4. a notice that refers to the disclaimer of warranties;
          5. a URI or hyperlink to the Licensed Material to the extent reasonably practicable;
        2. indicate if You modified the Licensed Material and retain an indication of any previous modifications; and
        3. indicate the Licensed Material is licensed under this Public License, and include the text of, or the URI or hyperlink to, this Public License.
      2. You may satisfy the conditions in Section 3(a)(1) in any reasonable manner based on the medium, means, and context in which You Share the Licensed Material. For example, it may be reasonable to satisfy the conditions by providing a URI or hyperlink to a resource that includes the required information.
      3. If requested by the Licensor, You must remove any of the information required by Section 3(a)(1)(A) to the extent reasonably practicable.
    2. ShareAlike. In addition to the conditions in Section 3(a), if You Share Adapted Material You produce, the following conditions also apply.
      1. The Adapter’s License You apply must be a Creative Commons license with the same License Elements, this version or later, or a BY-SA Compatible License.
      2. You must include the text of, or the URI or hyperlink to, the Adapter's License You apply. You may satisfy this condition in any reasonable manner based on the medium, means, and context in which You Share Adapted Material.
      3. You may not offer or impose any additional or different terms or conditions on, or apply any Effective Technological Measures to, Adapted Material that restrict exercise of the rights granted under the Adapter's License You apply.

    Section 4 – Sui Generis Database Rights.

    Where the Licensed Rights include Sui Generis Database Rights that apply to Your use of the Licensed Material:

    1. for the avoidance of doubt, Section 2(a)(1) grants You the right to extract, reuse, reproduce, and Share all or a substantial portion of the contents of the database;
    2. if You include all or a substantial portion of the database contents in a database in which You have Sui Generis Database Rights, then the database in which You have Sui Generis Database Rights (but not its individual contents) is Adapted Material, including for purposes of Section 3(b); and
    3. You must comply with the conditions in Section 3(a) if You Share all or a substantial portion of the contents of the database.

    For the avoidance of doubt, this Section 4 supplements and does not replace Your obligations under this Public License where the Licensed Rights include other Copyright and Similar Rights.

    Section 5 – Disclaimer of Warranties and Limitation of Liability.

    1. Unless otherwise separately undertaken by the Licensor, to the extent possible, the Licensor offers the Licensed Material as-is and as-available, and makes no representations or warranties of any kind concerning the Licensed Material, whether express, implied, statutory, or other. This includes, without limitation, warranties of title, merchantability, fitness for a particular purpose, non-infringement, absence of latent or other defects, accuracy, or the presence or absence of errors, whether or not known or discoverable. Where disclaimers of warranties are not allowed in full or in part, this disclaimer may not apply to You.
    2. To the extent possible, in no event will the Licensor be liable to You on any legal theory (including, without limitation, negligence) or otherwise for any direct, special, indirect, incidental, consequential, punitive, exemplary, or other losses, costs, expenses, or damages arising out of this Public License or use of the Licensed Material, even if the Licensor has been advised of the possibility of such losses, costs, expenses, or damages. Where a limitation of liability is not allowed in full or in part, this limitation may not apply to You.
    1. The disclaimer of warranties and limitation of liability provided above shall be interpreted in a manner that, to the extent possible, most closely approximates an absolute disclaimer and waiver of all liability.

    Section 6 – Term and Termination.

    1. This Public License applies for the term of the Copyright and Similar Rights licensed here. However, if You fail to comply with this Public License, then Your rights under this Public License terminate automatically.
    2. Where Your right to use the Licensed Material has terminated under Section 6(a), it reinstates:
      1. automatically as of the date the violation is cured, provided it is cured within 30 days of Your discovery of the violation; or
      2. upon express reinstatement by the Licensor.
      For the avoidance of doubt, this Section 6(b) does not affect any right the Licensor may have to seek remedies for Your violations of this Public License.
    3. For the avoidance of doubt, the Licensor may also offer the Licensed Material under separate terms or conditions or stop distributing the Licensed Material at any time; however, doing so will not terminate this Public License.
    4. Sections 1, 5, 6, 7, and 8 survive termination of this Public License.

    Section 7 – Other Terms and Conditions.

    1. The Licensor shall not be bound by any additional or different terms or conditions communicated by You unless expressly agreed.
    2. Any arrangements, understandings, or agreements regarding the Licensed Material not stated herein are separate from and independent of the terms and conditions of this Public License.

    Section 8 – Interpretation.

    1. For the avoidance of doubt, this Public License does not, and shall not be interpreted to, reduce, limit, restrict, or impose conditions on any use of the Licensed Material that could lawfully be made without permission under this Public License.
    2. To the extent possible, if any provision of this Public License is deemed unenforceable, it shall be automatically reformed to the minimum extent necessary to make it enforceable. If the provision cannot be reformed, it shall be severed from this Public License without affecting the enforceability of the remaining terms and conditions.
    3. No term or condition of this Public License will be waived and no failure to comply consented to unless expressly agreed to by the Licensor.
    4. Nothing in this Public License constitutes or may be interpreted as a limitation upon, or waiver of, any privileges and immunities that apply to the Licensor or You, including from the legal processes of any jurisdiction or authority.

View all instructions

Enjoy this project?



mark wrote 4 days ago point

Hi TegwynTwmffat.  The cost of your project could be justified if you have hectares of leeks.  

An alternative to fire is soil injected steam.  Safer for some fire prone environments.  The downside is the weight of the water.

  Are you sure? yes | no

Galane wrote 08/28/2017 at 06:31 point

You're re-inventing the Sizz-Weeder. That goes back at least to the late 1940's. It mounted to the back of a tractor and used thin flame jets to burn *really close* to the crop plants. For more mature plants and tougher crops like corn, the flames could be run across the crop plants to get the small weeds between them in the row - when the tractor was run fast enough so the flame would barely warm the larger plants.

The Sizz-Weeder seems to have fallen out of use with the rise of chemical herbicides.

  Are you sure? yes | no

K.C. Lee wrote 05/04/2017 at 16:25 point

"I say we take off and nuke the entire site from orbit. It's the only way to be sure."  :)

  Are you sure? yes | no

TegwynTwmffat wrote 05/04/2017 at 16:35 point

Yeah ..... We should colonise Mars ....... But you can bet that some weeds will find a way to stow-away onto the space rocket :(

  Are you sure? yes | no

Emach00 wrote 05/04/2017 at 16:15 point

After watching your video, never before have I become so emotionally invested in the success of another man's leek patch. :)

  Are you sure? yes | no

TegwynTwmffat wrote 05/04/2017 at 16:23 point

He he ....... Yes it's quite a dramatic video. The music is from Terminator Salvation by Danny Elfman.

  Are you sure? yes | no

Similar Projects

Does this project spark your interest?

Become a member to follow this project and never miss any updates