Eclipse 2017: Was Einstein Right?

While most people who make the trek to the path of totality for the Great American Eclipse next week will fix their gazes skyward as the heavenly spectacle unfolds, we suspect many will attempt to post a duck-face selfie with the eclipsed sun in the background. But at least one man will be feverishly tending to an experiment.

On a lonely hilltop in Wyoming, Dr. Don Bruns will be attempting to replicate a famous experiment. If he succeeds, not only will he have pulled off something that’s only been done twice before, he’ll provide yet more evidence that Einstein was right.

Eddington’s Expedition

Back in 1915, Albert Einstein first presented a set of field equations he had been working on for eight years. After publishing his Special Theory of Relativity, he searched for ways to work gravitation into his new framework, and finally hit upon a set of nonlinear and fiendishly difficult equations that describe how space and time must curve under the influence of matter and radiation.

Arthur Eddington. Source:
Wikimedia Commons

The physics community took a keen interest in Einstein’s General Theory of Relativity and began looking for ways to prove it. One of the predictions of the theory is gravitational lensing, or the deflection of light by massive bodies (lensing is also a prediction of Newtonian physics, but Einstein’s field equations predict about twice the deflection of light as the classical model). Measuring this effect, though, is no mean feat, mainly because the one thing massive enough and close enough to quantifiably bend light also happens to be really bright itself — the Sun.

What was needed was a total solar eclipse, and conveniently enough, one would occur in May of 1919. With only four years to go, and with the world torn by war, Sir Arthur Stanley Eddington planned a scientific expedition to the island of Principe off the west coast of Africa. He took a series of photographs of stars in the Hyades cluster, and through careful measurement found that Einstein’s predictions were correct. The publication of his results the next year made a huge splash in the popular press, instantly catapulting Einstein into the public eye and kicking off the age of Relativity.

Easier Said Than Done

Curiously, although many other experiments were later conducted to further bolster General Relativity, the Eddington eclipse experiment wasn’t repeated until over half a century later. It’s easy to understand why, though. First, total solar eclipses aren’t exactly common phenomena, and ones that make landfall in accessible locations with at least the hope of good viewing conditions are rare indeed. And until recently, the equipment needed to capture high-quality images with enough precision to measure the vanishingly small gravitational influence of our modest little star was bulky, finicky, and heavy. The sole repeat of the Eddington experiment was a 1973 expedition, again to Africa, that used 6 tons of equipment to generate a single usable image on a 12″ glass plate. The data from the image was good enough to confirm the Eddington results, though.

Advances in optics have made replication of the original experiment a more approachable endeavor lately, but there’s not much call for optical verification of a theory that’s been repeatedly verified by other methods over the last century. In fact, for confirmation of both General and Special Relativity, you need look no further than your smartphone, which uses both equations to correct the time signals from the cloud of GPS satellites orbiting overhead. That’s millions of verifications of the theory, every second of every day.

Why Bother?

Don Brun’s eclipse rig: refractor telescope, CCD camera, heavy mount, and tripod. Concrete pad not included. Source: Sky and Telescope

So why is Don Bruns bothering? Why will he be on that Wyoming mountain, praying for clear skies and low winds? Why has he rounded up the best amateur astronomy gear he can find, made multiple dry runs, scouted locations, and even gotten permission to pour a concrete pad to ensure his telescope won’t move during the two minutes of totality? Why has he gone to the extremes he has?

Don’s short answer is that he’s doing it for the challenge. When he first started mulling over the project, it seemed like the advances in optics, CCDs, and computers since 1973, not to mention since 1919, would make replication a breeze. As it turns out, 2017 will not be astronomical cake walk for Don. There are very few bright stars close enough to the sun to provide good points of reference, and the data on their non-deflected coordinates tends to be of poor precision. He needs to measure deflections on the order of 0.01 arcsecond. To put that into perspective, that would be like measuring the length of a pencil in Paris while observing it from New York.

Add to these challenges that Don has just over two minutes of totality, which is pretty short for a total eclipse, and an errant cloud, a gust of wind on his high Wyoming peak, or a forgotten detail could ruin years of effort. No matter what your background, as hackers we can all see that Don has set himself a lofty goal, and we can all relate to the stress he’ll be feeling as the Moon’s shadow comes racing toward his instrumented perch on August 21. As I’m watching totality end from my vantage point in Idaho, I’ll be thinking of Don and hoping that the stress turns into the elation that comes when everything works and your data gives you a glimpse of the workings of nature.

Filed under: Featured, History, Interest, Original Art

Alexa In A Bunny Rabbit

The Raspberry Pi is the perfect candidate for Google’s AIY where you can talk to a cardboard box with some electronics in it. [BuddyCasino] took on the challenge of squeezing an Alexa Client in an ESP32 and to make things interesting, a bunny rabbit was chosen as the host of the virtual assistant.

A few months ago, we did a teardown of the Google AIY Kit where [BuddyCasino] commented that he managed to port the Echo Dot client into and ESP32. Sure enough, the video below shows a demonstration of the build in action. The project uses the MAX98357A which is the same I2S DAC used in the Google AIY Voice Hat. For the microphone, the device is again an I2S component however unlike the Google AIY kit which uses the SPH0645LM4H, [BuddyCasino] opted for the ICS-43434.

Two NeoPixels are employed as visual indicators for various purposes. This project is an excellent example of how simple and cheap modern-day designs have become. We are hoping to see the author add more features to the design and who knows maybe we will see a Google Assistant port on the ESP32 in the future. Check out the original teardown for more inspiration.

Filed under: misc hacks

You Probably Don’t Want To Find This Toilet In Your Washroom

Ok, this one is a bit bizarre, but in perfect keeping with the subject matter: a talking toilet ripped from the pages of the Captain Underpants children’s books. user [hamblin.joe]’s county fair has a toilet decorating contest and at the suggestion of their neighbour’s son, [hamblin.joe] hatched a plan to automate the toilet using an Arduino in the fashion of the hero’s foes.

Two Arduinos make up this toilet’s brains, an Adafruit Wave Shield imbues it with sound capabilities, and a sonic wave sensor will trigger the toilet’s performance routine when someone approaches. A windshield wiper motor actuates the toilet bowl lid via a piece of flat iron bar connected to a punched angle bracket. Installing the motor’s mount was a little tricky, since it had to be precisely cut so it wouldn’t shift while in the toilet bowl. A similar setup opens the toilet tank’s lid, but to get it working properly was slightly more involved. Once that was taken care of there was enough room left over for a pair of 12V batteries and a speaker. Oh, and a pair of spooky eyes and some vicious looking teeth.

If you have a limited number of bathrooms at home or at work, some signage would be useful to know when it’s free and how dangerous it is to enter.

Filed under: Arduino Hacks, Uncategorized

GuitarBot Brings Together Art and Engineering

Not only does the GuitarBot project show off some great design, but the care given to the documentation and directions is wonderful to see. The GuitarBot is an initiative by three University of Delaware professors, [Dustyn Roberts], [Troy Richards], and [Ashley Pigford] to introduce their students to ‘Artgineering’, a beautiful portmanteau of ‘art’ and ‘engineering’.

The GuitarBot It is designed and documented in a way that the three major elements are compartmentalized: the strummer, the brains, and the chord mechanism are all independent modules wrapped up in a single device. Anyone is, of course, free to build the whole thing, but a lot of work has been done to ease the collaboration of smaller, team-based groups that can work on and bring together individual elements.

Some aspects of the GuitarBot are still works in progress, such as the solenoid-activated chord assembly. But everything else is ready to go with Bills of Materials and build directions. An early video of a strumming test proof of concept used on a ukelele is embedded below.

GuitarBot would fit right in to a band where only the instruments operate unplugged. Speaking of robot bands, don’t forget the LEGO-enabled Toa Mata, or the fully robotic group Compressorhead.

Filed under: musical hacks, robots hacks

The Latest Hacker Camp Badge Comes From BornHack

If you’re a fan of outdoor hacker camps, or if you’re a SHACamp attendee who’s still coming down from the event high, you may already know about the upcoming BornHack 2017 hacker camp on the Danish island of Bornholm, from the 22nd to the 29th of this month. It’s a smaller camp than many of the others on the calendar, but it makes up for that with a quite reasonable ticket price, a much longer duration, and a location that is a destination in itself.

Today we have news of the BornHack badge announcement, and though the details are a little sketchy it’s safe to say that there should be plenty there to keep attendees occupied. The irregularly-shaped PCB contains a Silicon Labs “Happy Gecko” EFM32 ARM Cortex M0 microcontroller, a 128×64 pixel OLED display, and the usual array of I/O lines. There is no information about its connectivity as it seems the BornHack folks prefer to run a teaser campaign, but we’d be surprised if there wasn’t some kind of wireless module on the reverse.

Barring a transportation miracle it’s unlikely that any of the Hackaday team will be making it to BornHack, but that’s our loss. It may not be one of the larger camps, but it looks to offer no less of the atmosphere you’d expect from a European hacker camp. At the time of writing there are still BornHack tickets to be had, so head on over to their website if you fancy a week at a hacker camp on a Danish island.

Filed under: cons

A Gas Model Made of Magnets

Magnets are great stuff and everyone loves them, there are so many things you can do with them, including creating a model of the crystalline structure of solids, just as [Cody´s Lab] did using a bunch of magnets inside a pair of plexiglass sheets.

Crystal structure of ice. Image from Wikemedia Commons.

Many materials have their atoms arranged in a highly ordered microscopic structure — a crystal — including most metals, rocks, ceramics and ice, among others. The structure emerges when the material solidifies looking for the minimum energy configuration. Every atom interacts with its neighbors via microscopic forces forming several patterns depending on the specific material and conditions.

In his macroscopic world, [Cody´s Lab] used the magnets as his “atoms” and the magnetic repulsion between them represent the microscopic forces. Confining the magnets inside two transparent walls, one can see the formation of the crystal structure as magnets are added one by one.

This is an excellent teaching resource and also a fun way to play with magnets if you want to give it a try. Or if you want another magnet hack, we have tons of them, including implanting them in your body, or making your own with 3D printing.

Filed under: misc hacks

Use a Drill to Power Your Flipbooks

[WolfCat] of Wolfcatworkshop is creating a hand-animated split-flap animation. But what do you use to test your animation once it’s on the split-flaps? Well, to test it out, [WolfCat] used a drill to give it motion. DoodlersAnonymous has some pics and an interview with [WolfCat] about his animation and there are some pictures on his Instagram page.

Technically, what [WolfCat] wanted to make is a “mutoscope,” a hand-cranked precursor to the movie projector that had its heyday in the late 19th and early 20th century. Originally installed in penny arcades and the like, mutoscopes were single-viewer apparatus. The viewer cranks the handle and the animated cards inside rotate around, stopped briefly by a bit of metal at the top in order to show a frame. The basic idea is similar to the way split-flap clocks or signs work.

[WolfCat] hand drew the animation for his movie and then scanned and printed out each frame. The frames were then transferred to a pair of flaps. [WolfCat] wanted to see how it would look when animated, but didn’t have any plans at the time for a case or a hand crank, so he found the closest tool that would do the job – a cordless drill. Attaching the drill and using a bit of card or wood as a stopper, [WolfCat] could see how the end result would look and could then start work on the case and crank.

The drill is a quick and easy way to see what the finished product would look like. Once he’s got it working, [WolfCat] could check out this 3D printed mutoscope case, or this flip dot animated display.

Filed under: hardware

Hackaday Prize Entry: A Bracelet for the Blind

The World Health Organization estimates that around 90% of the 285 million or so visually impaired people worldwide live in low-income situations with little or no access to assistive technology. For his Hackaday Prize entry, [Tiendo] has created a simple and easily reproducible way-finding device for people with reduced vision: a bracelet that detects nearby objects and alerts the wearer to them.

It does its job using an ultrasonic distance sensor and an Arduino Pro Mini. The bracelet has two feedback modes: audio and haptic. In audio mode, the bracelet will begin to beep when an object is within 2.5 meters. And it behaves the way you’d expect—get closer to the object and the beeping increases; back away and it decreases. Haptic mode involves two tiny vibrating disk motors attached to small PVC cuffs that fit on the thumb and pinky. These motors will buzz differently based on the person’s proximity to a given object.  If an object is 1 to 2.5 meters away, the pinky motor will vibrate. Closer than that, and it switches over to the thumb motor.

To add to the thriftiness of this project, [Tiendo] re-used other objects where he could. The base of the bracelet is a cuff made from PVC. The nylon chin strap and plastic buckle from a broken bike helmet make it adjustable to fit any wrist. To keep the PVC cuff from chafing, he slipped small pieces from an old pair of socks on to the sides.

It’s easy to see why this project is a finalist in our Best Product contest. It’s a simple, low-cost assistive device made from readily available and recycled materials, and it can be built by anyone who knows a little bit about electronics. Add in the fact that it’s lightweight and frees up both hands, and you have a great product that can help a lot of people. Watch it beep and buzz after the break.

Filed under: The Hackaday Prize, wearable hacks

Pouring 1200° Tea: Foundry in a Fire Extinguisher

Let’s face it — the design of most home foundries leaves something to be desired. Most foundries are great at melting metal, but when it comes to pouring the melt, awkward handling can easily lead to horrific results. That’s why we appreciate the thought that went into this electric melting pot foundry.

Sure, electric foundries lack some of the sex-appeal of gas- or even charcoal-fueled foundries, but by eschewing the open flames and shooting sparks, [Turbo Conquering Mega Eagle] was able to integrate the crucible into the foundry body and create what looks for all the world like a Thermos bottle for molten aluminum.

The body is a decapitated fire extinguisher, while the crucible appears to just be a length of steel pipe. An electric stove heating element is wrapped around the crucible, PID control of which is taken care of by an external controller and solid state relay. Insulated with Pearlite and provided with a handle, pours are now as safe as making a nice cup of 1200° tea.

You’ll perhaps recall that [Turbo Conquering Mega Eagle] has a thing for electric foundries, although we have to say the fit and finish of the current work far exceeds his previous quick-and-dirty build using an old electric stove.

[via r/metalworking]

Filed under: misc hacks, tool hacks

Wideband Woes and the Junkbox Miata

As ever, I am fighting a marginally winning battle against my 1991 Mazda MX-5, and this is the story of how I came to install a wideband oxygen sensor in my Japanese thoroughbred. It came about as part of my ongoing project to build myself a viable racecar, and to figure out why my 1990s Japanese economy car engine runs more like a late 1970s Malaise-era boat anchor.

I’ve always considered myself unlucky. My taste for early 90s metal has meant I’ve never known the loving embrace of OBD-2 diagnostics, and I’ve had to make to do with whatever hokey system was implemented by manufacturers who were just starting to produce reliable fuel injection systems.

Narrowband oxygen sensor voltage output. The output is heavily dependent on sensor temperature and highly non-linear, making these sensors unsuitable for delivering a true AFR reading.

This generally involves putting in a wire jumper somewhere, attaching an LED, and watching it flash out the trouble codes. My Mazda was no exception, and after putting up with a car that was running rich enough to leave soot all over the rear bumper, I had to run the diagnostic.

It turned up three codes – one for the cam angle sensor, and two for the oxygen sensor. Now, a cam angle sensor (CAS) fault will normally prevent the car running at all, so it’s safe to assume that was an intermittent fault to keep an eye on.

The oxygen sensor, however, was clearly in need of attention. Its job is to allow the engine control unit (ECU) to monitor the fuel mixture in the exhaust, and make sure it’s not too rich or too lean. As my car was very obviously running too rich, and the diagnostic codes indicated an oxygen sensor failure, a repair was in order.

I priced up replacement sensors, and a new oxygen sensor could be had for under $100. However, it wasn’t exactly what I wanted, as not all oxygen sensors are created equal. Cars in the 80s and 90s typically shipped from the OEM fitted with what’s called a narrowband oxygen sensor. These almost always consist of a zirconia dioxide cell that outputs a voltage depending on the difference in oxygen concentration between the exhaust gas and the free air. These sensors generally sit at 0.45 V when the fuel mixture is stoichiometric, but rapidly change to 0.1 V in a lean condition and 0.9 V in a rich condition. The response is highly non-linear, and changes greatly with respect to temperature, and thus is only good for telling the ECU if it’s rich or lean, but not by how much. ECUs with narrowband sensors tend to hunt a lot when running in closed loop O2 control – you’ll see an engine at idle hunt either side of the magical 14.7 stoichiometric air fuel ratio, never able to quite dial in on the correct number.

As I intend to switch to an aftermarket ECU in the future, I’ll need to tune the car. This involves making sure the air/fuel ratios (AFRs) are correct, and for that I need to be able to properly measure them. Just knowing whether you’re rich or lean isn’t enough, as often it’s desirable to run the engine intentionally rich or lean at certain engine loads. To get a true AFR reading requires fitting a wideband oxygen sensor. These are a little more complicated.


Wideband sensors were first perfected in 1992 by NGK, and consist of a narrowband sensor combined with a special ion pump cell mounted in a small measurement cavity that has an orifice for exhaust gas to feed in. The wideband control module monitors the oxygen concentration in the measurement cavity through the narrowband sensor, and if it detects a rich condition, it controls the pump cell current to pump oxygen ions from the outside air into the cavity to consume the excess fuel molecules. In a lean condition, it reverses the pump cell current to evacuate excess oxygen ions from the measurement cavity. The wideband oxygen controller can determine the true air fuel ratio by monitoring the pump current required to keep the measurement cavity at a stoichiometric mixture.

As a wideband oxygen sensor system costs only around $250, it didn’t make sense for me to buy another narrowband sensor when I had to upgrade to a wideband later anyway. I chose the Innovate LC-2 wideband controller kit with the DB gauge. This comes with a Bosch 4.9 wideband O2 sensor, the LC-2 controller, all the cabling required to install & program the controller, as well as a nice green LED 52 mm gauge so you can regale your dates with your highly accurate knowledge of your car’s air fuel ratio. The LC-2 is a good controller for a setup like mine, as it includes an emulated narrowband signal output. This allows me to use the wideband controller with my stock ECU, while I save up for an aftermarket unit that can understand the wideband outputs.

The first step prior to install was to run a calibration on the wideband controller. To do this, the controller must be powered up with no sensor attached, and left for approximately 30 seconds until the LEDs flash correctly. Then, the controller must be powered down, and then powered back up with the sensor attached. I did this using a bench power supply, however the calibration failed as it could only deliver 1 amp which wasn’t enough for the sensor’s heater. A second attempt using an ATX power supply which could deliver more current was successful.

The main requirements of the install are switched twelve-volt power for the wideband controller. It’s important to find a power line that’s only on when the ignition is in the ON position. This is because the wideband sensor has a heater to keep it at the right temperature for measurement. If you run this directly off twelve volts from the battery, it will drain the battery even when the car is off, and also burn out the sensor. As my car is focused more on performance than creature comforts, I decided to commit to having no stereo in the car. If you insist on leaving your stereo installed, you may want to run a separate fused twelve-volt line instead.

With the stereo gone, I decided to install the gauge where the car stereo would normally go, and ran this off the same power lines, which was easy enough as a few LEDs only require a couple hundred milliamps at most. My father was kind enough to fab up a stereo blanking panel to fit the gauge into which looked incredibly tidy once installed.


The LC2 comes set up with two analog outputs, one wideband on the yellow line and the aforementioned emulated narrowband output on the brown line. I ran the wideband output directly to the gauge and ran the emulated narrowband output on a wire heading all the way back to the engine bay. It was easier to splice into the stock ECU’s oxygen sensor lines there, rather than fighting with a mess of wires under the glovebox. The trick was to cut a small slit in the main engine harness grommet on the firewall to pass my new O2 sensor line through.

Quick-splice connections – just say no.

It was when I was running this wire that I realised the likely cause of the original O2 sensor failure. A previous owner had installed custom exhaust headers, which necessitated moving the original oxygen sensor to a new position. As the harness wasn’t the right size, they’d cut the original sensor’s line and spliced it together with a “quick-splice” connector. These things are universally awful and make terrible connections, and should never be used in an automotive environment, not even for a radio. This is almost certainly the reason the ECU wasn’t able to get a proper reading from the original oxygen sensor!

This grommet may come in handy if you’re choosing a similar layout for your wideband install!

Next I had to figure out how to route the cable from the wideband controller inside the cabin to the sensor mounted in the exhaust. American Miata owners typically pass this through a spare grommet on the driver’s side of the firewall, however those of us that drive on the opposite side of the road don’t have this available. Working on an Australian-delivered car, I was instead able to find a grommet perfectly located on the passenger side footwell for a small air conditioning hose, and crammed my cable through there instead.

Unfortunately, the worst was yet to come. It was time to install the new sensor into the exhaust. The problem was the absolute butcher who installed the sensor previously. The sensor had been completely cross threaded and torqued to an ungodly level. After much soaking in penetrating oils, I was able to remove the old sensor, but the threads were now completely gacked, to use the technical term. There was no hope of properly installing the new sensor without first sorting them out.

This brave old sensor stepped into the breech and acted as a tap, allowing me to chase the threads in the exhaust and save the day.

Those who know me well will be aware that I don’t exactly work in the most well-stocked garages. The correct sized tap would allow me to quickly clean up the threads without much issue, but I own as many taps as I do double-decker buses. With the clock having struck midnight, there was absolutely zero hope of a trip down to the store either. Thankfully, this is where the junkyard expeditions of my youth came to save me.

In previous years, having tried to troubleshoot one of my former rides, I’d procured a couple of second-hand oxygen sensors from the junkyard. I was lucky enough to find one still lying around, and it was called up for duty. Very delicately, I inserted it into the sensor bung in the exhaust, getting it as straight and parallel as possible, before gingerly beginning to torque it down. Going a half-turn or so at a time, and then backing off a quarter, as is the technique, I managed to cut a serviceable thread back into the exhaust, and saved the day. The new Bosch 4.9 wideband sensor was thoughtfully already coated with anti-seize, and I was now able to gingerly thread it into place without further issue.

By this point, it was now 2AM and I was depending on this car to run so I could propel myself home to my nice, comfy bed. By some dumb stroke of luck, or perhaps because fundamentally getting this install right only depended on the correct soldering of six wires, it worked first time, and the gauge sprang into life reporting my engine’s AFRs! Once the engine was warm, one could plainly observe the ECU’s control loop hunting for a stoichiometric mixture either side of that magical 14.7 number. Success was sweet.

Overall, the install went remarkably smoothly for a project involving a 26-year-old car and some seriously stuck old parts. After several weeks of use I can report the sensor is functioning well, though my car’s fuel economy is still remarkably poor, meaning I must hunt further for other issues. I recommend anyone to take on this hack if you’re heading down a similar path of modification, and wish you all good luck with your own project cars. May they return to the streets before rust returns them to the earth of your back garden!




Filed under: car hacks, Featured, Original Art