Variable-Nozzle Ducted Fan Provides Fluid Dynamics Lessons

October 19, 2023 by Bryan Cockfield 15 Comments

Any student new to the principles of fluid dynamics will be familiar with Bernoulli’s principle and the Venturi effect, where the speed of a liquid or gas increases when the size of the conduit it flows through decreases. When applying this principle to real-world applications, though, it can get a bit more complex than a student may learn about at first, mostly due to the shortcomings of tangible objects when compared to their textbook ideals. [Mech Ninja] discovered this while developing a ducted fan based around an RC motor.

The ducted fan is meant to be a stand-in for a model jet engine, based around a high-powered motor generally designed for drone racing. Most of the build is 3D printed including duct system, but in order to improve the efficiency and thrust beyond simple ducting, [Mech Ninja] designed and built a variable nozzle to more finely control the “exhaust” of his engine. This system is also 3D printed and can restrict or open up the outflow of the ducted fan, much like a real jet engine would. It uses two servos connected to collars on the outside of the engine. When the servos move the collars, a set of flaps linked to the collars can choke or expand the opening at the rear of the engine.

This is where some of the complexity of real-life designs comes into play, though. After testing the system with a load cell under a few different scenarios, the efficiency and thrust weren’t always better than the original design without the variable nozzle. [Mech Ninja] suspects that this is due to the gaps between the flaps, allowing air to escape and disrupting the efficient laminar flow of the air leaving the fan, and plans to build an improved version in the future. Fluid dynamics can be a fairly complex arena to design within, sometimes going in surprising directions like this ducted fan that turned out better than the theory would have predicted, at least until they accounted for all the variables in the design.

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RF Remote Made Easy

July 31, 2023 by Bryan Cockfield 10 Comments

The 433 MHz spectrum is a little bit of an oddball. ~~It’s one of the few areas of the radio spectrum which is nearly universally unlicensed~~ Outside of the US, it’s an open playground for devices that adhere to the power restrictions and other guidelines about best practices. IoT devices operate here, as well as security systems and, of course, remote controls. And, using a few off-the-shelf parts [hesam.moshiri] shows us how to take advantage of this piece of spectrum by designing and building a programmable and versatile 4-channel 433 MHz remote control.

Built around an ATmega8 microcontroller, making it easy to work with Arduino sketches, and with a 2×8 character LCD for ease-of-use when not connected to a computer, the wireless switching device can store up to 80 remote control codes in its EEPROM memory. This was one of the harder parts for [hesam] to sort out, but using structures to store the data for the codes eventually solved the problems. A simple GUI makes using it with whatever remote happens to be on hand fairly straightforward, including the ability to record codes from existing remotes on the fly and also to associate those codes with specific actions.

Schematics and a bill of materials are available on the project’s page, making this fairly accessible to those looking to add some wireless connectivity to a project, home automation system, or IoT device. It’s mainly set up as a switching device, but with some modifications could be put to work doing more complex tasks. The 433 MHz spectrum is an exciting place to be, too, and things like setting up entire security systems using it are not too far removed from a switching device like this.

[Editor’s note: As many mentioned in the comments, 433 MHz is a licensed ham band in the USA (ITU Region 2), so you can’t use it without a license. (Get one, it’s easy.) In the USA, the equivalent band is at 315 MHz, which is why garage door remotes usually come with a 315/433 choice. Either way, check your local laws before you transmit.]

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Hackaday Prize 2023: OMOTE Universal Remote

July 15, 2023 by Tom Nardi 39 Comments

A good universal remote can help tame today’s complex home entertainment systems, combining both classic IR and more modern WiFi and Bluetooth connectivity with programmable functions that allow the user to execute multi-step operations with a single button. Unfortunately, programming them often involves the use of clunky proprietary software.

Which is why [Maximilian Kern] has developed the OMOTE. This open source universal remote is powered by the ESP32, and features the usual collection of physical buttons in addition to a 2.8” 320 x 240 touchscreen with a responsive graphical interface that can display more advanced user interfaces. Everything is packed into an ergonomic 3D printed case that gives it an exceptionally professional look.

The remote’s USB-C port can be used to recharge the internal 2,000 mAhA battery, as well as reprogram the ESP32’s firmware via a CH340C serial chip. The battery life is estimated to be about six months given the considerable low-power capabilities of the ESP32, which includes the use of a LIS3DH 3-axis accelerometer to keep the hardware in sleep mode until it’s picked up.

The software side is still in development, so the IR codes for the remote are currently hardcoded and its WiFi capabilities are limited to MQTT. But in the future, [Maximilian] imagines a web-based configuration interface that runs on the ESP32 and lets you add codes and setup the remote via your phone or desktop.

It looks like the hardware is more or less complete, so presumably the focus from here on out will be bringing the software across the finish line. Don’t worry, there’s still plenty of time — since it’s an entry into the Gearing Up challenge of the 2023 Hackaday Prize, the judges won’t pick the finalists until August 8th.

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The Remoteduino Nano Is A Tiny IR Remote That’s Truly Universal

June 18, 2023 by Robin Kearey 13 Comments

Universal remotes are extremely convenient if they work correctly. But setting them up can be quite a hassle: often, you need to browse through long lists of TV models, key in the codes on the remote with just a blinking LED as confirmation, and then pray that the manufacturer included the correct codes for all your equipment. IR isn’t a very complicated technology, however, so it’s perfectly possible to roll your own universal remote, as [sjm4306] shows in his latest project, the Remoteduino Nano. It’s a fully programmable IR remote that gives you maximum flexibility when emulating the codes for those obscure A/V systems scattered around your home.

The remote runs on an ATmega328p in a tiny QFN package, which drives a standard 5 mm IR LED through a transistor. Eight buttons are available to the user, which can be freely mapped to any desired code. A five-pin header is included to program the ATmega through its serial port. However, this was mainly done to help debug – a user who only needs to program the device once would typically use a pogo-pin-based adapter instead.

Currently, codes can only be programmed through the serial port, but there’s also an IR receiver present that can be used to copy codes from an existing remote. [sjm4306] hasn’t implemented this feature in software yet, but will probably do so in a future update of the project’s Arduino sketch. If you’re impatient, you can also have a go at it yourself since all code and the board’s Gerber files are freely available for download.

Its tiny size makes the Remoteduino Nano a convenient tool to keep in your drawer if you like to tinker with A/V systems and keep losing those remotes. The Nano is actually an improved version of the original Remoteduino project that [sjm4306] developed a couple of years ago. The problem of a truly universal remote is one that dates back several decades, however.

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All Aboard The Garbage Express

January 2, 2023 by Bryan Cockfield 39 Comments

Cog railways are a somewhat unusual way of train locomotion, typically only installed when a train needs to climb steep terrain. Any grade above about 10% needs the extra traction since the friction between the wheels and rails won’t be enough to push the train forward or keep it from falling backwards. Even without a steep hill to climb, sometimes a cog railway is necessary for traction as [Max Maker] discovered while building a train for his garbage cans.

The build started out as a way to avoid having to wheel his seven waste bins to the curb every month. Originally he built a more standard railway with a simple motor to drive the train, but he quickly realized that there wasn’t enough grip even when using plastic wheels, even though this track follows fairly flat terrain. Since the rail is built out of steel he quickly welded up a rack-and-pinion system to one of the rails. The build goes through many iterations before he finally settles on a design that solves the problem, and it includes several other features as well such as remote control and a spring-loaded automatic charger for the train at its station in the back yard.

While we always appreciate the eccentricity of those who would automate a relatively simple task that only happens once a month, [Max Maker] hopes to build this into a commercial product aimed at the elderly or disabled who would really benefit from a reliable, semi-automatic system that takes their trash bins to the curb for them. And, if your system only involves a single trash can, there are other ways of automating the task of taking the garbage to the curb.

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IR Remote tester in use, showing a remote control lighting up an LED and screenshots of the Arduino serial terminal

IR Remote Tester Helps You Crack The Code

November 8, 2022 by Dave Walker 15 Comments

Even though some devices now use WiFi and Bluetooth, so much of our home entertainment equipment still relies on its own proprietary infrared remote control. By and large (when you can find them) they work fine, but what happens when they stop working? First port of call is to change the batteries, of course, but once you’ve tried that what do you do next? [Hulk] has your back with this simple but effective IR Remote Tester / Decoder.

IR remote tester schematic showing arduino, receiver, LED and resistor — How to connect the TSOP4838 to an Arduino to read the transmitted codes

By using a cheap integrated IR receiver/decoder device (the venerable TSOP4838), most of the hard work is done for you! For a quick visual check that your remote is sending codes, it can easily drive a visible LED with just a resistor for a current-limit, and a capacitor to make the flickering easier to see.

For an encore, [Hulk] shows how to connect this up to an Arduino and how to use the “IRremote” library to see the actual data being transmitted when the buttons are pressed.

It’s not much of a leap to imagine what else you might be able to do with this information once you’ve received it – controlling your own projects, cloning the IR remote codes, automating remote control sequences etc..

It’s a great way to make the invisible visible and add some helpful debug information into the mix.

We recently covered a more complex IR cloner, and if you need to put together a truly universal remote control, then this project may be just what you need.

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24 Hours Of Le Airplanes

September 27, 2022 by Bryan Cockfield 22 Comments

There’s no more famous road endurance race than the 24 Hours of Le Mans, where teams compete to see how far they can drive in a single 24-hour window. The race presents unique challenges not found in other types of racing. While RC airplanes may not have a similar race, [Daniel] a.k.a. [rctestflight] created a similar challenge for himself by attempting to fly an RC airplane non-stop for as long as he could, and a whole host of interesting situations cropped up before and during flight.

In order for an RC plane to fly for an entire day, it essentially needs to be solar powered. A large amount of strategy goes into a design of this sort. For one, the wing shape needs to be efficient in flight but not reduce the amount of area available for solar panels. For another, the start time of the flight needs to be balanced against the position of the sun in the sky. With these variables more or less fixed, [Daniel] began his flight.

It started off well enough, with the plane in an autonomous “return to home” mode which allowed it to continually circle overhead without direct human control. But after taking a break to fly it in FPV mode, [Daniel] noticed that the voltage on his battery was extremely high. It turned out that the solar charge controller wasn’t operating as expected and was shunting a large amount of solar energy directly into the battery. He landed and immediately removed the “spicy pillow” to avoid any sort of nonlinear event. With a new battery in the plane he began the flight again.

Even after all of that, [Daniel] still had some issues stemming from the aerodynamic nature of this plane specifically. There were some issues with wind, and with the flight controller not recognizing the correct “home” position, but all in all it seems like a fun day of flying a plane. If your idea of “fun” is sitting around and occasionally looking up for eight and a half hours. For more of [Daniel]’s long-term autonomous piloting, be sure to take a look at his solar tugboat as well.

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