Misc Hacks

4136 Articles

Fitness Tracker Hacked Into Optical Density Meter

September 20, 2019 by 5 Comments

What do fitness trackers have to do with bacterial cultures in the lab? Absolutely nothing, unless and until someone turns a fitness band into a general-purpose optical densitometer for the lab.

This is one of those stories that shows that you never know from where inspiration is going to come. [Chinna Devarapu] learned that as a result of playing around with cheap fitness bands, specifically an ID107HR. A community has built up around hacking these bands; we featured a similar band that was turned into an EEG. With some help, [Chinna] was able to reflash the microcontroller and program it in the Arduino IDE, and began looking for a mission for the sensor-laden platform.

He settled on building a continuous optical densitometer for his biology colleagues. Bacterial cultures become increasingly turbid as the grow, and measuring the optical density (OD) of a culture is a common way to monitor its growth phase. This is usually done by sucking up a bit of the culture to measure, but [Chinna] and his team were able to use the hacked fitness band’s heartrate sensor to measure the OD on the fly. The tracker fits in a 3D-printed holder where an LED can shine through the growing culture; the sensor’s photodiode measures the amount of light getting through and the raw data is available via the tracker’s Bluetooth. The whole thing can be built for less than $20, and the plans have been completely open-sourced.

We really like the idea of turning these fitness bands into something completely different. With the capabilities these things pack into such a cheap and compact package, they should start turning up in more and more projects.

Stunning 4-Cylinder Solenoid Motor Should Be A Hit With Subaru Fans

September 18, 2019 by 47 Comments

As far as electric propulsion is concerned, the vast majority of applications make use of some kind of rotational motor. Be it induction, universal, brushed or brushless, these are the most efficient ways we have to do mechanical work with electricity. There are other, arcane methods, though – ones which [Maker B] explores with this 4-cylinder solenoid engine.

The principle of the solenoid engine is simple. Cylinders are wound with coils to act as solenoids, with the piston acting as the armature. When the solenoid is energised, it pulls the piston into the cylinder. The solenoid is then de-energised, and the piston can return to its initial position. The piston is coupled to a crankshaft via a connecting rod, and a flywheel is used to help the motor run continually. These are also known as reciprocating electric motors.

[Maker B]’s build is a 4-cylinder design in a boxer configuration. Produced with basic hand-operated machine tools, the build process is one to watch. Aluminium and brass are carefully crafted into the various components of the motor, and parts are delicately assembled with small fasteners and plenty of retaining compound. Solenoid timing is via a series of microswitches, installed neatly in the base of the motor and actuated by the crankshaft.

While solenoid motors are inefficient, they’re quite something to watch in action. This one is no exception, with the motor spinning up to 1100 rpm when running at 7.2 volts. We’d love to see some data on the power output and efficiency too. It’s possible to build solenoid motors in different configurations, too – this radial build is particularly fun. Video after the break.

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Arduino Bot Rocks A PS2 Controller

September 17, 2019 by 1 Comment

As far as controlling robots goes, makers today are spoilt for choice. WiFi and Bluetooth enabled microcontrollers are a dime a dozen, and integration with smartphone apps is a cinch. Despite this, the old methods still hold sway, as [Igor Fonseca] demonstrates with a simple Arduino bot.

It’s a classic build, using a tracked chassis with a pair of motors providing propulsion and skid steering. The motors are controlled by an L298N H-bridge board, with power courtesy of a trio of 18650 batteries. An Arduino Uno acts as the brains of the operation. Control is via a Playstation 2 controller, in this case a 2.4 GHz third party version. This allows the robot to be controlled wirelessly, with the decoding handled by [Bill Porter]’s useful Arduino library.

It’s a cheap approach to building a remote-controlled bot, and one that would be a great way to teach interested children about how to work with embedded systems. We’ve featured a similar build before, too. Video after the break.

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The Benefits And Pitfalls Of Using PCBs As An Enclosure

September 16, 2019 by 21 Comments

[Mastro Gippo] found himself in a pickle recently, with the development of an enclosure for the Prism electric vehicle charger. The body had been sorted out, but the front cover needed work. It had to be visually appealing, and ideally should provide the user feedback on the charging process. After some thought, [Mastro] decided to explore the possibilities of using a PCB as a part of a commerical product enclosure.

For a variety of reasons, using a specially designed PCB was an attractive solution for the team’s enclosure. Wanting something cost effective, easily customizable, and something that would help with emissions compliance, a PCB seemed like a great idea. With this in mind, [Mastro] prepared a series of prototypes. These feature see-through sections for LEDs to shine through, as well as a capacitive button and gold-plated logo. The fact that the front cover is a PCB makes the integration of the electronic components a cinch.

Before heading into full production, [Mastro] began to question why this technique isn’t used more often. Deciding to research further, [Bunnie Huang] was tapped to provide some advice on the concept. Noting that there can be issues with lead content, as well as the fact that PCBs aren’t often produced with proper regard to aesthetics, there were some pitfalls to the idea. Additionally, ESD testing can be difficult, while the in-built capacitive button would face issues in wet conditions.

None of these are showstoppers however, and [Mastro] has persevered, combining the front cover PCB with an adhesive plastic sheet for added protection. We fully expect that if more manufacturers explore this route, it may be a more viable technique in future. It’s also a great example of knowing when to ask others for help – it’s not the first time we’ve learned from [Bunnie’s] broad experience!

Walking Arm Trebuchet Is Different, But Effective

September 15, 2019 by 6 Comments

For many of us, our first encounter with the famous trebuchet was Age of Empires II, or perhaps a documentary on historical siege engines. However, many people continue to pursue builds of their very own, exploring designs new and old. The walking arm trebuchet is a good example, which uses an unconventional design to great effect.

The design eschews a rigid frame, instead consisting of simply an arm and a triangular leg assembly. The arm is held upside down, and is launched by allowing the trebuchet to collapse forward to rest on the triangular leg. The triangular leg is fitted with spikes which dig into the ground, and the arm then pivots around, launching the projectile. The design is reportedly quite efficient, similar to a floating arm trebuchet, with a very simple design. Performance was so good, it netted a clean sweep of the 2018 Vermont Pumpkin Chuckin’ festival.

There’s a wide variety of ways to go about building a trebuchet, and we’ve featured some before. You can even instrument your payloads to quantify performance. Video after the break.

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Wall-Mounted Ground Station Tames Unruly SatNOGS Node

September 12, 2019 by 8 Comments

For many of us, ad hoc projects end up having a certain permanence to them. Think of the number of Raspberry Pis and RTL-SDRs that are just dangling from a USB cable under a desk or stuffed behind a monitor, quietly going about their business. If it ain’t broke, don’t fix it.

Some projects, though, just end up accreting past the acceptable point. This wall-mounted SatNOGS ground station is a great example of what happens when something needs to be done about the mess. The pile of stuff that [cshields] had cobbled together over time for his ground station needed tidying, so he laid hands on a new Pi 4 and a cool enclosure/breadboard called a Stegoboard. This is just a piece of acrylic with a variety of holes laid out to match every imaginable PC board, hard drive, PC motherboard, Arduino, and just about anything out there that needs mounting. To contain the mess, he mounted the Pi and a 7″ touchscreen to the Stegoboard, along with an RTL-SDR and an Arduino to control his antenna rotator. The ground station wiring is still a little rough, but worlds better than what it was, and now that it’s mounted on the wall it’ll be much easier to use.

For those not familiar with SatNOGS, check out our article back from when the Satellite Network of Ground Stations won the 2014 Hackaday Prize. In the half-decade since then, SatNOGS has only grown, with a huge following of dedicated enthusiasts pointing their antennas at the sky. We know how to pick ’em, and we’ll be selecting the 2019 Hackaday Prize winner very soon.

Thanks to [elkos] for the tip.

Custom Lego Server Case Looks As Though It Came Straight From A Data Center

September 11, 2019 by 12 Comments

The picture above appears to show two unremarkable 2U rack servers, of the kind that are probably hosting the page you’re reading right now. Nothing special there – until you look carefully and realize that the rack server case on the left is made entirely from Lego. And what’s more, the server even works.

When it comes to building Lego computers, [Mike Schropp] is the guy to call. We’ve previously featured his Lego gaming computer, a striking case wrapped around what was a quite capable machine by 2016 standards, as well as an earlier case that reminds us a little of a NeXT. His reputation for Lego-clad computers led server maker Silicon Mechanics to commission a case for a trade show, and [Mike] jumped at the challenge.

Making a home-grade machine is one thing, but supporting all the heavy drives, power supplies, and fans needed to make the machine work is something else. He used a combination of traditional Lego pieces along with a fair sampling of parts from the Lego Technics line to pull off the build, which looks nearly perfect. Sadly, the Lego unit sizes make the case slightly taller than 2U, but that’s a small quibble when everything else matches so well, even the colors. And the fact that the server works, obviously important for a trade show demo, is pretty amazing too. The power supplies are even hot-swappable!

Congratulations to [Mike] on yet another outstanding Lego creation.