Posts | Comments

Planet Arduino

Archive for the ‘arduino hacks’ Category

Hackaday readers have certainly seen more than a few persistence of vision (POV) displays at this point, which usually take the form of a spinning LED array which needs to run up to a certain speed before the message becomes visible. The idea is that the LEDs rapidly blink out a part of the overall image, and when they get spinning fast enough your brain stitches the image together into something legible. It’s a fairly simple effect to pull off, but can look pretty neat if well executed.

But [Andy Doswell] has recently taken an interesting alternate approach to this common technique. Rather than an array of LEDs that spin or rock back and forth in front of the viewer, his version of the display doesn’t move at all. Instead it has the viewer do the work, truly making it the “Chad” of POV displays. As the viewer moves in front of the array, either on foot or in a vehicle, they’ll receive the appropriate Yuletide greeting.

In a blog post, [Andy] gives some high level details on the build. Made up of an Arduino, eight LEDs, and the appropriate current limiting resistors on a scrap piece of perfboard; the display is stuck on his window frame so anyone passing by the house can see it.

On the software side, the code is really an exercise in minimalism. The majority of the file is the static values for the LED states stored in an array, and the code simply loops through the array using PORTD to set the states of all eight digital pins at once. The simplicity of the code is another advantage of having the meatbag human viewer figure out the appropriate movement speed on their own.

This isn’t the only POV display we’ve seen with an interesting “hook” recently, proving there’s still room for innovation with the technology. A POV display that fits into a pen is certainly a solid piece of engineering, and there’s little debate the Dr Strange-style spellcaster is one of the coolest things anyone has ever seen. And don’t forget Dog-POV which estimates speed of travel by persisting different images.

[Thanks to Ian for the tip.]

Beyond pride, the biggest issue keeping adults off small motorized scooters is the fact that their tiny motors usually don’t have the power to move anything heavier than your average eighth grader. That didn’t stop [The_Didlyest] from snapping up this $7 thrift store find, but it did mean the hot pink scooter would need to be beefed up if it had any hope of moving 170 lbs of hacker.

Logically, the first step was fitting a more capable motor. [The_Didlyest] used an electric wheelchair motor which had a similar enough diameter that mounting it was fairly straightforward. The original sprocket and chain are still used, as are the mounting holes in the frame (though they had to be tapped to a larger size). That said, the new motor is considerably longer than its predecessor so some frame metal had to be cut away. This left the scooter without a kickstand and with a few inches of motor hanging out of its left side, but it’s all in the name of progress.

Naturally the upgraded motor needed similarly upgraded batteries to power it, so [The_Didlyest] put together a custom pack using eighteen 18650 cells spot welded together for a total output of 25V. Coupled with a 60A battery management system (BMS), the final 6S 3P configured pack is a very professional little unit, though the liberal application of duct tape keeps it from getting too full of itself.

Unfortunately the original motor controller consisted of nothing but relays, and didn’t allow adjusting speed. So that needed to go as well. In its place is a homebrew speed controller made with three parallel MOSFETs and an Arduino to read the analog value from the throttle and convert that into a PWM signal.

[The_Didlyest] says the rear tire is now in need of an upgrade to transmit all this new power to the road, and some gearing might be in order, but otherwise the scooter rebuild was a complete success. Capable of mastering hills and with a top speed of about 10 MPH, the performance is certainly better than the stock hardware.

Of course this is far from the first time we’ve seen somebody put a little extra pepper on a scooter. Some of them even end up being street-legal rides.

When building projects with a simple goal in mind, it’s not unheard of for us to add more and more switches, buttons, and complexity as the project goes through its initial prototyping stages. Feature creep like this tends to result in a tangled mess rather than a usable project. With enough focus, though, it’s possible to recognize when it’s happening and keep to the original plans. On the other hand, this single-button project with more than one use seems to be the opposite of feature creep. (YouTube, embedded below.)

[Danko]’s project has one goal: be as useful as possible while only using a single button and a tiny screen. Right now the small handheld device can be used as a stopwatch, a counter, and can even play a rudimentary version of flappy bird. It uses an Arduino Pro Mini, a 64×48 OLED screen running on I2C, and has a miniscule 100 mAh 3.7V battery to power everything. The video is worth watching if you’ve never worked with this small of a screen before, too.

Getting three functions out of a device with only one button is a pretty impressive feat, and if you can think of any other ways of getting more usefulness out of something like this be sure to leave it in the comments below. [Danko] is no stranger to simple projects with tiny screens, either. We recently featured his homebrew Arduino calculator that uses an even smaller screen.

Certain hobbies come in clusters. It isn’t uncommon to see, for example, ham radio operators that are private pilots. Programmers who are musicians. Electronics people who build model trains. This last seems like a great fit since you can do lots of interesting things with simple electronics and small-scale trains. [Jimmy] at the aptly-named DIY and Digital Railroad channel has several videos on integrating railroad setups with Arduino. These range from building a DCC system for about $45 (see below) to a crossing signal.

There are actually quite a few basic Arduino videos on the channel, although most of them are aimed at beginners. However, the DCC — Digital Command and Control — might be new to you if you are a train neophyte. DCC is a standard defined by the National Model Railroad Association.

Model trains pick up electrical power from the rails. DCC allows digital messages to also ride the rail. The signal shifts from positive to negative to indicate marks and spaces. By diode switching the electrical signal, the train or other equipment can get a constant supply of current. However, equipment monitoring the line ahead of the diodes can read the data and interpret it as commands.

To accommodate old equipment, you can stretch the high or low values to make the average voltage either positive (forward) or negative (reverse). This can heat up DC motors, though, so it may shorten the life of the legacy equipment.

The build uses an available Arduino library, so if you want to get into the protocol you’ll have to work through that code. We had to wonder if there were other places where passing power and data on the same lines might be useful. There are other ways to do that, of course, but this would be a reasonable place to start if you needed that capability.

If you want to use an mBed system instead of an Arduino, there’s a great tutorial for that. Either way, it is just the thing for your next coffee table.

Certain hobbies come in clusters. It isn’t uncommon to see, for example, ham radio operators that are private pilots. Programmers who are musicians. Electronics people who build model trains. This last seems like a great fit since you can do lots of interesting things with simple electronics and small-scale trains. [Jimmy] at the aptly-named DIY and Digital Railroad channel has several videos on integrating railroad setups with Arduino. These range from building a DCC system for about $45 (see below) to a crossing signal.

There are actually quite a few basic Arduino videos on the channel, although most of them are aimed at beginners. However, the DCC — Digital Command and Control — might be new to you if you are a train neophyte. DCC is a standard defined by the National Model Railroad Association.

Model trains pick up electrical power from the rails. DCC allows digital messages to also ride the rail. The signal shifts from positive to negative to indicate marks and spaces. By diode switching the electrical signal, the train or other equipment can get a constant supply of current. However, equipment monitoring the line ahead of the diodes can read the data and interpret it as commands.

To accommodate old equipment, you can stretch the high or low values to make the average voltage either positive (forward) or negative (reverse). This can heat up DC motors, though, so it may shorten the life of the legacy equipment.

The build uses an available Arduino library, so if you want to get into the protocol you’ll have to work through that code. We had to wonder if there were other places where passing power and data on the same lines might be useful. There are other ways to do that, of course, but this would be a reasonable place to start if you needed that capability.

If you want to use an mBed system instead of an Arduino, there’s a great tutorial for that. Either way, it is just the thing for your next coffee table.

We always think that crossing the Atlantic in a blimp would be very serene — at least once they put heaters on board. The Hindenburg, the R-101, and the Shenandoah put an end to the age of the airship, at least for commercial passenger travel. But you can still fly your own with a helium balloon and some electronics. One notable project — the Blimpduino — has evolved into the Blimpduino 2. The open-source software is on GitHub. We couldn’t find the PCB layout, so we aren’t sure if it is or will be open. The 3D printed parts are available, though.

The PCB is the heart of the matter, a four-layer board with an ARM M0 processor, an ESP8266 WiFi module, four motor outputs, two motor outputs, a 9-axis inertial navigation system, an altimeter, and a forward object detection system. There’s also a battery charger onboard.

The standard set up uses three props: two for thrust and one for altitude. There’s a smartphone app and apparently, you can even have a copilot with a second phone. The lifting body is a mylar balloon with helium and they say the control is suitable even for a very large balloon. The altimeter data is from a time-of-flight sensor and there’s also a pressure transducer with temperature sensor if you want to measure higher altitudes.

We couldn’t embed the video, but there’s one of people flying the things through hoops on the website. You can, however, see a promotional video, below. As you might expect, payload capability is very low and so 3D printed parts have low infill and the board is made to be light.

Of course, our own [Sophi Kravitz] has been building her drone blimp army for some time and we are waiting for her attempt at world domination any day now. If you are in the mood for something lower tech, you can always rip apart a toy car and add your own balloon.

 

Sometimes, traveling the internet feels a little like exploring an endless cave system looking for treasure. Lots of dark passageways without light or life, some occasional glimmers as you find a stray gold doubloon or emerald scattered in a corner. If we take the metaphor too far, then finding [Paul]’s “Little Arduino Projects” repository is like turning an unremarkable corner only to discover a dragon’s hoard.

LEAP (as [Paul] also refers to the collection) is a numbered collection of what looks like more or less every electronics project he has completed over the last few years. At the time of writing there are 434 projects in the GitHub repository and tagged and indexed in a handy blog-style interface. Some are familiar, like a modification to a Boldport project. Others are one-off tests of a specific concept like driving a seven segment display (there are actually 16 similar projects if you search the index for “7-Segment”). On the other end are project builds with more detailed logs and documentation, like the LED signboard for monitoring the status of 24 in-progress projects, mounted in a guitar fret board.

LEAP reminds us of the good old days on the internet, before it felt like 50% trolling and 50% tracking cookies. Spend a few minutes checking out [Paul]’s project archive and see if you find anything interesting! We’ve just scratched the surface. And of course, send a tip if you discover something that needs a write-up!

There is something fascinating about watching an autonomous machine. An automatic car wash, a soda vending machine that picks up the product behind a window, a plotter, or a robot like a CNC or 3D printer are all interesting to watch. Although [EngineerDog] bills Mug-O-Matic as a tiny CNC, we think it is more of a plotter for coffee mugs. It’s still fun to watch though, as you can see in the video below.

The design has about 60 printed parts and uses a Sharpie at the business end. It accepts gcode and can even emblazon your favorite mug with our own Jolly Wrencher, so you know we like it.

Of course, a Sharpie mark won’t stay on a mug forever, but the write up says you can bake the mug to make the markings permanent. At first, the project used a cheap Arduino Nano breakout board. However, that was set up to drive the servos with the Arduino’s power supply, so instead of board surgery there is now a custom PCB.

The resulting drawings are a little shaky, we aren’t sure if that’s from the way the device mounts on top of the mug or just the lever arm of the carriage the pen rides in. However, for a fun project it does a great job.

We couldn’t help but think about eggbots and the spherebot when we saw this. We also wondered if this could draw on glass that would later be etched with hydrofluoric acid or  Armour Etch.

We don’t think [bleepbit] will take offense when we say the “poor man’s theremin” looks cheesy — after all, it was built in a cheese container. Actually, it isn’t a bad case for a simple device, as you can see in the picture and the video below. Unlike a traditional theremin, the device uses ultrasonics to detect how far away your hand is and modifies the sound based on that.

There are also two buttons — one to turn the sound off and another to cycle through some effects. We liked how it looked like a retro cassette, though. The device uses a cheap Arduino clone, but even with a real Arduino, the price wouldn’t be too bad. However, the price tag quoted doesn’t include a few connectors or the speaker that appears in the schematic. There’s a note that the model built uses a jack instead of a speaker, but it would be nice to include both and use the kind of jack that disconnects the speaker when you plug speakers or headphones in.

The code is simple and there are four possible effects you can cycle through with one of the buttons. Unlike a real theremin, you can trigger this one with anything the ultrasonic sensor can see. The Arduino audio quality is not superb, of course, but it is still a fun rainy day project.

We couldn’t help but think that a 32-bit Arduino could have used one of the sophisticated audio libraries. However, there are other libraries that might improve things even with the 8-bit processor.

Granted, this isn’t a true theremin, but we’ve seen plenty of those, too. We’ve even used the same sensors to control a PC.

A Raspberry Pi with a camera is nothing new. But the Pixy2 camera can interface with a variety of microcontrollers and has enough smarts to detect objects, follow lines, or even read barcodes without help from the host computer. [DroneBot Workshop] has a review of the device and he’s very enthused about the camera. You can see the video below.

When you watch the video, you might wonder how much this camera will cost. Turns out it is about $60 which isn’t cheap but for the capabilities it offers it isn’t that much, either. The camera can detect lines, intersections, and barcodes plus any objects you want to train it to recognize. The camera also sports its own light source and dual servo motor drive meant for a pan and tilt mounting arrangement.

You can connect via USB, serial, SPI, or I2C. Internally, the camera processes at 60 frames per second and it can remember seven signatures internally. There’s a PC-based configuration program that will run on Windows, Mac, or Linux. You can even use the program to spy on the camera while it is talking to another microcontroller like an Arduino.

The camera isn’t made to take sharp photos or video, but it is optimized for finding things, not for picture quality. High-quality frames take more processing power, so this is a reasonable trade. The camera does need training to find objects by color and shape. You can do the training with the PC-based software, but you can also do it with a self-contained procedure that relies on a button on the camera. The video shows both methods.

Once trained, you can even have an Arduino find objects. There’s a library that allows you to find how many items the camera currently sees and find out what the block is and its location. The identification clearly depends highly on color, so you’ll probably need to experiment if you have things that are different colors on different sides or has multiple colors.

Sure, you could use a sufficient computer with OpenCV to get some of these results, but having this all in one package and usable from just about any processor could be a real game-changer for the right kind of project. If you wanted to make a fancy line-following robot that could handle 5-way intersections and barcode commands this would be a no-brainer.

We’ve seen other smart cameras like OpenMV before. Google also has a vision processor for the Pi, too. It has a lot of capability but assumes you are connecting to a Pi.



  • Newsletter

    Sign up for the PlanetArduino Newsletter, which delivers the most popular articles via e-mail to your inbox every week. Just fill in the information below and submit.

  • Like Us on Facebook