FAQ

GENERAL

What is OpenMower?

OpenMower is a project that modifies an existing commercial Lawn mower robot (currently the Yard Force 500) with better steering electronics to provide, among other things, GPS navigation and optimized mowing paths. See the intro video here: https://www.youtube.com/watch?v=BSF04i3zNGw

Can I buy an assembled OpenMower or a kit?

No, at present it is a DIY yourself project that will require effort and technical skill on your part. But there is a very active community, so help is available.

How much does it cost?

Approx €350 for the mower + €400 for RTK GPS + €100 (yeah, semiconductor shortage..) for a Raspberry Pi + €200 for custom hardware.

Who created OpenMower?

Clemens Elflein, known as @c.ez in the project's Discord is the designer and creator of OpenMower. If you like what he is doing, please support him on Patreon

What is the current stage of the project

The OpenMower is running in prototype at @c.ez. The mainboard and ESC work fine, just the STM32 for the ESCs are currently expensive. Therefore we're working on a cheaper motor controller alternative. A group of early builders are buying parts and getting ready to “co-build” with @c.ez to test and validate the design.

Where can I find more information?

The entry points for more information are:

• The Discord for the project
• Annoncements
• This FAQ
• Important links to GitHub, the YouTube channel etc.

What license is OpenMower based on?

The license is “Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International Public License”, pls. see here: https://creativecommons.org/licenses/by-nc-sa/4.0/

BUILDING AN OPENMOWER YOURSELF

What skills do I need to build one?

• Taking hardware apart and putting it together again
• Buying parts
• Soldering, in particular SMD techniques for making the main PCB
• Electronics, getting Linux and ROS on a Raspberry Pi, probably installing some packages etc.
• Debugging, patience, tech creativity, joy in participating

What should I do if I want to build an OpenMower?

Remember, we are very early stage, so don’t expect finished build instructions, rather be prepared to figure out quite a bit of stuff yourself (with the help of the community). That said, head to the #open-mower-builds in the Discord and be part of an exciting activity.

What can I do right now if I want to build?

Start getting parts! Look at the preliminary BOM in https://wiki.openmower.de/index.php?title=Building_the_Mower and start getting the big chunks, like the YardForce 500, Raspberry Pis, GPS RTK modules etc.

Start following the #open-mower-builds Discord channel here

Should I order a PCB for the main board right now?

Not yet. @c.ez is currently awaiting a shipment of rev 0.9.1.beta of the main board. Once he has validated that, we should be able to start ordering.

Is there a step-by-step instruction?

Not yet. @c.ez is working on it.

Is there a recommended place to buy parts?

Unfortunately, no. Best EU suggestions are Farnell, Mouser, Digikey.

If anyone has better suggestions, pls. share in #open-mower-builds on the Discord and it will be included here.

Where do I buy Raspberry Pis?

RPIs have a serious world-wide shortage at the moment. You may check https://rpilocator.com/ if they point to anywhere that has supply.

If you find EU vendors with supply, pls. share in #open-mower-builds in the Discord.

OPENMOWER TECH - GENERAL

Can I use a different mower than the YardForce 500?

The project is designed for the YF500, so the immediate answer is no. The project is solely focused on making the YF500 work at the moment. However, YF500 seems to be one branding of a Chinese robot that appears under other names, too. So likely, we’ll discover that other brands (and also other models of Yard Force) can work. Also some builders in the Discord are looking into robots from other manufacturers to see if the core OpenMower tech could be applied to those. Check #mower-dissection if you want to follow or participate. But applying to other brands will likely not happen before the YF500 based OpenMower seems to run well.

It is very likely that you can hack a solution for another mower than the YF500 if you have the appropriate hardware skills and understand the YF500 implementation in great detail. But if you want to have the support of the main project, be aware that it is focused on the YF500 for now.

Where can I buy the Yard Force 500?

• Amazon.de.
• Beware of myrobotcenter - they seem to have gone bankrupt.

If you find other good vendors, pls. share in #open-mower-builds on the Discord and it will be included here.

Is Yard Force 500 available in the US?

It seems not directly. You may try to import it from Amazon in the EU. Those that have it confirm that it operates on 100-240 V~, 50/60 Hz, 56 W.

If you find a consistent way to obtain a YF500 or a compatible mower in the US, pls. share in #open-mower-builds on the Discord and it will be included here.

What is special about the OpenMower?

• OpenMower utilizes two GPS RTK units (one on the Mower, the other in a fixed place) to allow OpenMower to have centimeter-precise location data.
• That means that you can train OpenMower on your lawn edge and it can run without a boundary wire. And you can train it on several lawn segments that it can then roam between.
• The exact location info allows OpenMower to cut along an efficient planned path rather than move chaotically around like almost every commercial mower out there.
• You build it yourself and all the soft- and hardware is open source, so if you have the skills, you can mod it further.

What technological platforms is OpenMower based on?

• The Mower
  • Raspberry Pi SBC version 4 running Linux and ROS 1 for the robotics; mapping and navigation etc.
  • GPS RTK module communicating with a fixed GPS RTK module to provide cm accuracy
  • Raspberry Pi Pico (microcontroller) to operate sensors such as the IMU, battery voltage & charge current, "stop" button, lift sensor in front wheels etc...
• The GPS base station
  • GPS RTK module for providing a point of reference to provide cm accuracy in conjunction with the module on the mower

WHAT ABOUT MOWERS THAT ARE NOT YARD FORCE 500?

ArduMower https://www.ardumower.de/

ArduMower is a slightly more mature but also more closed project, also using RTK GPS and no wire. You can get both an assembled mower and a full kit.

As @c.ez# writes, it depends on your preference: "So basically: If you're looking to build an robotic mower as fast as possible, I'd recommend you to go with the Ardumower. If you're in for the tech, I recommend you to follow this project instead (!!obviously biased opinion here!!)". See his full post here: https://discord.com/channels/958476543846412329/961804411112394842/963271459357204560

Navimow https://navimow.segway.com/

Navimow is a new system that seems to be still not quite launched on the market (as per 2022-04-19). It looks to be quite full-featured and should offer a commercial out-of-the box solution with app and many features. Price point seems to be €1.300.

ReP_AL mowers https://repalmakershop.com/

ReP_AL has a mower that that you build yourself, based on a 3D print design that you can print yourself or buy from them. You buy the kit of all parts. They say "Fully autonomous robot lawn mower with TFT Touchscreen and Smartphone APP.  The mower project includes the mower itself a boundary wire control station, smartphone APP, TFT Touchscreen interface and an optional charging station." The mover control is Arduino based and the software is open source. There is some indications that they are moving towards GPS RTK.

What do we know about the feasibility of doing OpenMower on other mowers?

In the #mower-dissection channel on the Discord, members are taking apart other brands/models from Yard Force 500 to assess the viability of applying the OpenMower platform to them. There is also a Google Sheet with collected notes and observations here: https://docs.google.com/spreadsheets/d/1BX0-KEs5v-VED8-RA4BLE-wRdXHtlmcKy4n9K5vJVAA/edit?usp=sharing

Ask @tinker0436 for edit permission if you want to contribute.

A note on other mowers and future direction

It is likely that in a later version, the OpenMower platform could be split in "core" and "specific mower" parts so that many mowers could be supported and it would be easy to hack OpenMower onto your mower. But at the current stage, the project is focused on realizing a working beta on the Yard Force 500, There are already individual builders that are experimentally trying to adapt OpenMower to their owen mower platforms.

About the Yard Force 500

Can the YF500 be made to mow more than 500 square meters?

First: The area that the producers report are highly approximate. The reason being that traditional robotic mowers cut at random, so in a given time, they eventually cover the entire lawn more or less intensively. Hence, it is all approximate. Many owners of the traditional robots cover more area than the robots are made out for, simply by having them run a lot over a week, thus with the many hours of mowing per week, covering an area larger than specified for a given mower.

That said, it is quite likely that OpenMower on YF500 has more direct capacity than 500 square meters - since it mows systematically and covers every bit of lawn only once. We still have no reports on how many square meters the YF500 can cover on one charge, but as we start having actual OpenMowers out there, we can report on that.

We might later set up the software to have the mower return and pick up again where it left off upon an empty battery - but that is not implemented yet. It should be doable in software, though, and thus be able to increase the area that it is possible to cover.

Lastly, there seems to be extra physical space for more battery in the YF500 under the battery pack, but it has not been investigated yet. Be aware, that it takes knowledge to work with the batteries. You should know what you are doing, since the batteries contain a lot of power and may explode or combust if handled incorrectly.

OPENMOWER TECH - SPECIFICS

RTK GPS

Which RTK GPS modules are used in the basic OpenMower design?

These ones: https://www.ardusimple.com/product/simplertk2b-basic-starter-kit-ip65/

How many RTK GPS modules are needed for OpenMower?

In the actual phase 1 design, 2 are needed, one at base and one on the mower. The one on the mower is mandatory to measure exact position. The one at base provides reference. Without the reference, the exact location of the mower can not be determined. See a good explanation of this here: https://www.ardusimple.com/rtk-explained/

The reference may - possibly - be provided instead by publicly available servers that can provide local correction data. One of these solutions is NTRIP. Using such a source, it should be possible to not have the RTK GPS module on the base, but instead subscribe to the correction signal from the internet. Two notes regarding that: 1) The current design does not have this out of the box, so you would have to modify the ROS code yourself for this setup. And 2) if the Internet-based correction signal becomes unavailable, your mower will lose cm-precise location and cannot navigate. With the basic design with two RTK modules, that is not a problem.

How do the two RTK GPS modules communicate with each other - what are the options?

The original OpenMower implementation has a separate process running which receives the RTK corrections from an NTRIP server via WiFi and redirects them to the GPS board. The IP is set to the base station in the local network, you can update it to an external service provider though.

This has the drawback, that you constantly need to be connected to the WiFi.

Alternatively, the ArduSimple board has a slot where you can plug an external radio as direct bridge between the robot and the base station for extended range. ArduSimple offers multiple modules for this and they will all work plug and play with the OpenMower, since the OpenMower expects corrected data and does not care how the GPS receives the corrections. If you are using this though, you might need to edit your GPS configuration (see ArduSimple manual) and disable the NTRIP receiver process in ROS.

Maintenance of this FAQ

This FAQ is maintained by @tinker0436

It is a work in progress. If you have additional questions or comments or find stuff missing, use the Discord #open-mower channel and tag a @Mod so that we get a ping. Comments and suggestions are very welcome!

Disclaimer

This FAQ is provided as-is and free of charge. No guarantees of any kind are made that the information contained herein is exact or correct or does not violate any local regulations or cause any security risk. Any use you make of any information given here is at your own discretion and risk.