RC Lawnmower Is Built To Last

August 2, 2022 by Danie Conradie 17 Comments

Mowing the lawn is one of those tasks that someone will always be optimizing or automating. To allow him to mow the lawn while seated comfortably in the shade, [Workshop from Scratch] built an RC Lawnmower in his signature solid steel frame style.

The chassis consists of a heavy welded steel frame from square tubing, with a pair of knobbly go-kart wheels on the back and large caster wheels on the front. The actual grass-cutting part is a 173cc petrol lawnmower engine with a steel hull, mounted on an articulating subframe which can be remotely raised and lowered using a linear actuator. The rear wheels are attached to a pair of custom sprocket hubs, driven via chain by two 200 W geared DC motors to allow skid steering.

The motors and electronics are powered by a set of 18 Ah lead-acid batteries wired in parallel. The petrol engine can also charge the batteries, but its current isn’t enough to keep up while mowing. However, it does help to extend the range. All the electronics are housed in a plastic enclosure with a power switch, key start for the engine, and battery charge indicator on the lid. The power from the batteries runs through a pair of automotive relays connected to the power switch and a set of fuses for protection. For safety [Workshop from Scratch] wired a relay to the engines’ coil to shut it off remotely, or when the radio link to the controller is lost. An action cam was also mounted on the electronics box to stream a first-person view to a smartphone over WiFi.

Overall this is a very well built project, especially mechanically, and looks like the perfect platform for further self-driving using Ardurover. [rctestflight] has demonstrated the capabilities of the open source autopilot with several rovers, including a tiny lawnmower that cuts grass with Exacto blades.

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The Rollercoaster Of Developing The Ultimate Hackable Keyboard

August 2, 2022 by Danie Conradie 14 Comments

When designing anything with “hackable” in the punchline, scope creep is an integral part of the process. You end up trying to create something to potentially be an infinite number of things for an infinite number of users. [Zack Freedman] is going really deep down the rabbit hole with his MiRage keyboard and has been documenting the progress in his usual entertaining style, with some cautionary notes included.

The most fascinating tale from this come about as a result of adding RGB LEDs beneath the keys, while still allowing everything to function when the keyboard is split in two. Thanks to an IO expander chip in one side of the board, a standard TRRS audio cable is enough to link both sides together. But the addition of addressable LEDs meant more lines were required.

[Zack] thought he had found a solution in the form of SATA cables, but it turns out all SATA cables internally connect pins 1,3, and 7, making them useless for this application. He realized he had no choice but to add a second microcontroller to the “dumb” side of the keyboard and return to I2C over a TRRS cable. However, the RP2040-based Seeed XIAO’s I2C absolutely refused to play along. After a fortnight of frustrating debugging, it turns out there was a bug in the pin definitions. Fortunately, this also revealed that the XIAO had an undocumented secondary I2C interface, which he plans to configure as a peripheral to make the keyboard almost infinitely expandable with additional keys.

An earlier version of the MiRage featured tactile OLED displays, but it turns out the thin panes of glass don’t handle repeated flexing well, so they had to be scrapped. In their place came a touchscreen E-paper display, but now this seems to be evolving into a pluggable module for any input device that your heart desires, including possibly a haptic SmartKnob. Another major update are PCB footprints that support both CHOC and MX switches.

It all started with the MiRage V1 keyboard intended to for use in an updated version of [Zack]’s cyberdeck. After realizing how many people were interested in the keyboard but not the cyberdeck, he shifted focus to refining the MiRage.

This project still has some way to go, so we’ll certainly be keeping our eye on it. In the meantime, we’ve recently covered another exceptionally customizable keyboard that might catch your fancy.

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Hoverboard Powered Sofa Is Fun And A Bit Dangerous

August 2, 2022 by Danie Conradie 8 Comments

Discarded hoverboards are a great source of free high torque motors for hacking. This can include crazy but fun projects like this hoverboard-driven IKEA sofa, as demonstrated by [Bitluni] and his friends at xHain Hackerspace in Berlin.

With a couple of dead hoverboards in various conditions and a working e-bike battery, the group started exploring different options to put together a usable drivetrain. The first attempt involved commanding the motor drivers directly by intercepting communication from the gyro-based controller. The 9-bit communication protocol was a tough nut to crack, so they tried (and failed) to use the gyro-boards directly as the controllers. In the process of researching they discovered someone had created alternative firmware for the hoverboard controllers to allow control with a Wii Nunchuck. There is even a web-based config tool for compiling the firmware.

With some wood spacers screwed to the bottom of the sofa, the hoverboard motors could be attached by simply screwing their enclosure to the bottom of the couch and adding a section of PVC pipe between the halves for wiring. Caster wheels were added to the rear corners of the sofa to complete the chassis. The motors were very sensitive to control inputs on the Nunchuck, so riding the couch tended to rapidly turn into a rodeo event. The couch also wasn’t made to carry its load on the outer corners, so it had to be reinforced with plywood after it started cracking.

We’ve seen plenty of hacks that involve hoverboard motors, including an electric skateboard with mecanum wheels and a surprisingly practical e-bike conversion.

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OpenDendrometer Can Measure How Your Tree Feels

August 1, 2022 by Danie Conradie 12 Comments

There are various ways to measure plant health, and we’ve seen many projects creating open-source solutions. One we haven’t seen is a dendrometer, which involves measuring various physical dimensions of trees to track their health and growth. [John Opsahl] is changing this with the OpenDendrometer, a tool for tracking the diameter of tree limbs and fruit.

Tiny changes in diameter take place throughout the day, and tracking these changes allows deviations to be detected, which can be a sign of water stress. Over weeks and months, these measurements can be used to measure growth and fruits’ progress to harvest. [John] found that a digital tire tread depth gauge can work well for this application. Many of these gauges use the same electronics as the cheap digital calipers, for which the serial protocol was reverse engineered more than a decade ago. The OpenDendrometer connects the tire depth gauge to a microcontroller via a 1.5V level shifter, which logs measurements to an SD card while using a DS3231 RTC for accurate timestamps. The RTC can also be used to wake up the circuit at the required intervals to save battery power. For the initial proof of concept [John] is using an Arduino Pro Mini, but plans to move to an ESP32 at a later stage to allow wireless data transmission.

Everything will be housed in a 3D printed enclosure with a foam cord gasket to make the device weather resistant. A mounting rod on the outside of the enclosure with adjustable thumbscrews allows the OpenDendrometer to be attached to any part of the tree. We plan to keep an eye on this project and look forward to seeing the data it produces.

For the other ways of measuring plant health, we’ve covered everything from soil moisture to Normalized Difference Vegetation Index and even plant weight and even pot plant weight.

Simple Propulsion For The Lazy Paddle Boarder

August 1, 2022 by Danie Conradie 14 Comments

One of the downsides to healthy outdoor activities is all the exercise. Who would want to do that if you can build something to do the hard work for you? That seems to be the theme of [Bitluni]’s latest build, a simple (and hacky) propulsion system for a stand-up paddleboard.

After acquiring an inflatable stand-up paddleboard and trying it out a few times, [Bitluni] decided to skip the “stand up” and “paddle” parts. He designed and printed a very simple propeller, which he intended to power with a brushless motor and speed controller. In the process of drilling out the prop to fit the shaft, he realized he was overcomplicating things. So he decided to just use his battery-powered drill instead. For the shaft tube, he modified an old crutch by drilling a hole in the handle for the shaft and adding a duct with a bearing on the other end. He also attached a carabiner to the handle to fix it to the paddleboard.

A test at a lake showed that the propulsion system performed relatively well for a proof of concept but had some flaws. To submerge it properly, [Bitluni] had to sit on the rear of the paddleboard facing backward. If it was too close to the surface, it would suck air and lose thrust, or spray him and his drill with water. Of course, there is also the real risk of drowning his drill in the process.

Projects don’t need to be complex to be enjoyable, and you can often learn more by quickly creating a proof of concept instead of taking forever to come up with the “perfect” design.

If you want to see some more advanced water-borne projects, check out the waterjet-powered electric surfboards built by [RCLifeOn] and [Andrew W].

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R2Home Is Ready To Bring Back Your High Altitude Payload

August 1, 2022 by Danie Conradie 23 Comments

With high-altitude ballooning, you are at the mercy of the winds, which can move your payload hundreds of kilometers and deposit it in some inaccessible spot. To solve this [Yohan Hadji] created R2Home, an autonomous parachute-based recovery system that can fly a payload to any specified landing site within its gliding range.

We first covered R2Home at the start of 2021, when he was still in the early experimental phases, but the project has matured massively since then. It just completed its longest and highest test flight. Descending autonomously from a release altitude of 3500 m, with an additional radiosonde payload, it landed within 5 m of the launch point.

R2Home electronics with it's insulated enclosure — R2Home electronics with its insulated enclosure

R2Home can fly using a variety of steerable canopies, even a DIY ram-air parachute, as demonstrated in an earlier version. [Yohan] is currently using a high-performance wing for RC paragliders.

A lot of effort went into developing a reliable parachute deployment system. The main canopy is packed carefully in a custom “Dbag”, which is attached to a drogue chute to stabilize the system during free-fall and deploy the main canopy at a preset altitude. This is done with a servo operated release mechanism, while steering is handled by a pair of modified winch servos intended for RC sailboats.

All the electronics are mounted on a stack of circular 3D printed brackets which fit in a tubular housing, bolted together with threaded rods. With the help of a design student [Yohan] also upgraded the simple tube housing to a lockable, foam-insulated design to help it handle temperatures at high altitudes.

The flight main flight computer is a Teensy 4.1 plugged into a custom PCB to connect all the navigation, communication, and flight systems. The custom Arduino-based autopilot takes inputs from a GPS receiver, and pilots the system to the desired drop zone, which it circles until touchdown.

The entire project is extremely well documented, and all the design files and code are open source and available on Github. Continue reading “R2Home Is Ready To Bring Back Your High Altitude Payload” →

Trippy Bicycle Uses Multiple Partial Wheels

July 31, 2022 by Danie Conradie 18 Comments

Bicycles need at least two wheels to be rideable, but [The Q] realized you don’t necessarily need the wheels to be in one piece. As long as you have at least two points of rolling contact with the ground, you can spread the load across multiple partial wheels. He demonstrated this by splitting the rear wheel of his bike first in half and then thirds to create an absolute head turner.

Since a conventional bicycle wheel with tensioned spokes would collapse if cut apart, [The Q] used single-piece aluminum wheels instead. The tires were cut into pieces, and the inner tubes were replaced with sections of thick-walled HDPE pipe that won’t collapse under the weight of a human. The tires and the HDPE “inner tubes” were riveted to the wheels.

To mount the additional wheels on the frame, [The Q] welded a set of extensions to the back with mounting points for the partial wheels. To keep them synced, timing is done with chains running on sprockets welded to the disc brakes. In the second video, he tries to also split the front wheels, but found the front forks can’t handle the torque and would flex dangerously when the contact point is too far forward. Instead, he settled for three wheels on the back.

Much like his hubless bicycle, it’s not designed to be better than a standard bicycle, but is excellent for attracting attention. Though at least in some situations, the all-wheel drive bike he built last year might come in handy.

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