Arduino-Powered Rocket Test Stand

December 14, 2018 by Tom Nardi 10 Comments

If you’re into amateur rocketry, you pretty quickly outgrow the dinky little Estes motors that they sell in the toy stores. Many hobbyists move on to building their own homebrew solid rocket motors and experimenting with propellant mixtures, but it’s difficult to know if you’re on the right track unless you have a way to quantify the thrust you’re getting. [ElementalMaker] decided he’d finally hit the point where he needed to put together a low-cost test stand for his motors, and luckily for us decided to document the process and the results.

The heart of the stand is a common load cell (the sort of thing you’d find in a digital scale) coupled with a HX711 amplifier board mounted between two plates, with a small section of vertical PVC pipe attached to the topmost plate to serve as a motor mount. This configuration is capable of measuring up to 10 kilograms with an 80Hz sample rate, which is critically important as these type of rocket motors only burn for a few seconds to begin with. The sensor produces hundreds of data points during the short duration of the burn, which is perfect for graphing the motor’s thrust curve over time.

Given such a small window in which to make measurements, [ElementalMaker] didn’t want to leave anything to chance. So rather than manually igniting the motor and triggering the data collection, the stand’s onboard Arduino does both automatically. Pressing the red button on the stand starts a countdown procedure complete with flashing LED, after which a relay is used to energize a nichrome wire “electronic match” stuck inside the motor.

In the video after the break you can see that [ElementalMaker] initially had some trouble getting the Arduino to fire off the igniter, and eventually tracked the issue down to an overabundance of current that was blowing the nichrome wire too fast. Swapping out the big lead acid battery he was originally using with a simple 9V battery solved the problem, and afterwards his first test burns on the stand were complete successes.

If model rockets are your kind of thing, we’ve got plenty of content here to keep you busy. In the past we’ve covered building your own solid rocket motors as well as the electronic igniters to fire them off, and even a wireless test stand that lets you get a bit farther from the action at T-0.

Continue reading “Arduino-Powered Rocket Test Stand” →

Every Computer Deserves A Rotary Encoder

December 13, 2018 by Tom Nardi 26 Comments

In the era of touch screens and capacitive buttons, we’d be lying if we said we didn’t have the occasional pang of nostalgia for the good old days when interfacing with devices had a bit more heft to it. The physical clunk and snap of switches never seems to get old, and while you can always pick up a mechanical keyboard for your computer if you want to hear that beautiful staccato sound while firing off your angry Tweets, there’s a definite dearth of mechanical interface devices otherwise.

[Jeremy Cook] decided to take matters into his own hands (literally and figuratively) by designing his own multipurpose USB rotary input device. It’s not a replacement for the mouse or keyboard, but a third pillar of the desktop which offers a unique way of controlling software. It’s naturally suited to controlling things like volume or any other variable which would benefit from some fine tuning, but as demonstrated in the video after the break even has some gaming applications. No doubt the good readers of Hackaday could think of even more potential applications for a gadget like this.

The device is built around the diminutive Arduino-compatible PICO board by MellBell, which features a ATmega32u4 and native USB. This allowed him to very rapidly spin up a USB Human Interface Device (HID) with minimal headaches, all he had to do was hang his buttons and rotary encoder on the PICO’s digital pins. To that end, he [Jeremy] used the fantastic I2C rotary encoder designed by [fattore.saimon], which readers may remember as a finalist in the Open Hardware Design Challenge phase of the 2018 Hackaday Prize. He also added a NeoPixel ring around the encoder to use for some visual feedback and because, well, it just looks cool.

Since all of the core components are digital, there’s not a whole lot required in the way of wiring or passive components. This let [Jeremy] put the whole thing together on a piece of perfboard, freeing him up to spend time designing the 3D printed enclosure complete with translucent lid so he can see the NeoPixel blinkenlights. He got the tolerances tight enough that the whole device can be neatly press-fit together, and even thought to add holes in the bottom of the case so he could push the perfboard back out if he needed to down the line.

[Jeremy] spends a good chunk of the video going over the software setup and development of the firmware, and details some of the nuances he had to wrap his head around when working with the I2C encoder. He also explains the math involved in getting his encoder to emulate a mouse cursor moving in a circle, which he thinks could be useful when emulating games that originally used an encoder such as Tempest or Pong.

We’ve seen similar USB “knobs” in the past for controlling volume, but the additional inputs that [Jeremy] built into his version definitely makes it a bit more practical. Of course we’re suckers for interesting USB input devices to begin with.

Continue reading “Every Computer Deserves A Rotary Encoder” →

Christmas POV Display Makes Viewer Do The Work

December 9, 2018 by Tom Nardi 12 Comments

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.]

Thrift Store Razor Scooter Gets More Kick

December 5, 2018 by Tom Nardi 27 Comments

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.

Many Uses For A Single Button

December 5, 2018 by Bryan Cockfield 18 Comments

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.

Continue reading “Many Uses For A Single Button” →

The Arduino Hits The Rails

November 30, 2018 by Al Williams 14 Comments

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.

Continue reading “The Arduino Hits The Rails” →

Blimpduino Hits Version 2

November 27, 2018 by Al Williams 17 Comments

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 servo motor outputs, a 9-axis inertial navigation system, an altimeter, and a forward object detection system. There’s also a battery charger onboard.

Continue reading “Blimpduino Hits Version 2” →