Author: Dan Maloney

3373 Articles

Persistence Of Phosphorescence Clock Displays YouTube Stats Too

April 5, 2018 by 21 Comments

Looking for an eye-catching and unique way to display the time and date? Want the flexibility to add other critical information, like the number of YouTube subs you’ve got? Care to be able to read it from half a block away, at least at night? Then this scrolling glow-in-the-dark dot-matrix display could be right up your alley.

Building on his previous Morse code transcriber using a similar display, [Jan Derogee] took the concept and went big. The idea is to cover a PVC pipe with phosphorescent tape and rotate it past a row of 100 UV LEDs. The LEDs are turned on as the glow-in-the-dark surface passes over them, charging up a row of spots. The display is built up to two rows of 16 characters by the time it rotates into view, and the effect seems to last for quite a while. An ESP8266 takes care of driving the display and fetching NTP time and YouTube stats.

We’ve seen “persistence of phosphorescence” clocks before, but not as good looking and legible as this one. We like the approach, and we can’t help but think of other uses for glow-in-the-dark displays.

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Kapton: Miracle Material With A Tragic History

April 4, 2018 by 64 Comments

On a balmy September evening in 1998, Swissair flight 111 was in big trouble. A fire in the cockpit ceiling had at first blinded the pilots with smoke, leaving them to rely on instruments to divert the plane, en route from New York to Geneva, to an emergency landing at Halifax Airport in the Canadian province of Nova Scotia. But the fire raging above and behind the pilots, intense enough to melt the aluminum of the flight deck, consumed wiring harness after wiring harness, cutting power to vital flight control systems. With no way to control the plane, the MD-11 hit the Atlantic ocean about six miles off the coast. All 229 souls were lost.

It would take months to recover and identify the victims. The 350-g crash broke the plane into two million pieces which would not reveal their secrets until much later. But eventually, the problem was traced to a cascade of failures caused by faulty wiring in the new in-flight entertainment system that spread into the cockpit and doomed the plane. A contributor to these failures was the type of insulation used on the plane’s wiring, blamed by some as the root cause of the issue: the space-age polymer Kapton.

No matter where we are, we’re surrounded by electrical wiring. Bundles of wires course with information and power, and the thing that protects us is the thin skin of insulation over the conductor. We trust these insulators, and in general our faith is rewarded. But like any other engineered system, failure is always an option. At the time, Kapton was still a relatively new wonder polymer, with an unfortunate Achilles’ heel that can turn the insulator into a conductor, and at least in the case of flight 111, set a fire that would bring a plane down out of the sky.

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What’s The Deal With Transparent Aluminum?

April 3, 2018 by 139 Comments

It looks like a tube made of glass but it’s actually aluminum. Well, aluminum with an asterisk beside it — this is not elemental aluminum but rather a material made using it.

We got onto the buzz about “transparent aluminum” as a result of a Tweet from whence the image above came. This Tweet was posted by [Jo Pitesky], a Science Systems Engineer at the Jet Propulsion Lab in Pasadena. [Jo] reported that at a recent JPL technology open house she had the chance to handle a tube of material that looks for all the world like a section of glass tubing, but was billed as transparent aluminum. [Jo] tweeted this because it was an interesting artifact that few people get to play with and she’s right, this is fascinating!

The the material itself is intriguing, and I immediately had practical questions like what is this stuff? What is it good for? How is it made? And is it really aluminum rendered transparent by some science fiction process?

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Pavement Projection Provides Better Bicycle Visibility At Night

April 2, 2018 by 68 Comments

Few would question the health benefits of ditching the car in favor of a bicycle ride to work — it’s good for the body, and it can be a refreshing relief from rat race commuting. But it’s not without its perils, especially when one works late and returns after dark. Most car versus bicycle accidents occur in the early evening, and most are attributed to drivers just not seeing cyclists in the waning light of day.

To decrease his odds of becoming a statistics and increase his time on two wheels, [Dave Schneider] decided to build a better bike light. Concerned mainly with getting clipped from the rear, and having discounted the commercially available rear-mounted blinkenlights and wheel-mounted persistence of vision displays as insufficiently visible, [Dave] looked for ways to give drivers as many cues as possible. Noticing that his POV light cast a nice ground effect, he came up with a pavement projecting display using four flashlights. The red LED lights are arranged to flash onto the roadway in sequence, using the bike’s motion to sweep out a sort of POV “bumper” to guide motorists around the bike. The flashlight batteries were replaced with wooden plugs wired to the Li-ion battery pack and DC-DC converter in the saddle bag, with an Arduino tasked with the flashing duty.

The picture above shows a long exposure of the lights in action, and it looks very effective. We can’t help but think of ways to improve this: perhaps one flashlight with a servo-controlled mirror? Or variable flashing frequency based on speed? Maybe moving the pavement projection up front for a head-down display would be a nice addition too.

Assess Your Output With A Cheap DIY Urine Flowmeter

April 1, 2018 by 35 Comments

Some things about the human body are trivial to measure. Height, weight, blood pressure, pulse, temperature — these are all easily quantifiable with the simplest of instruments and can provide valuable insights into our state of health. Electrical activity in the heart and the brain can be captured with more complex instruments, too, and all manner of scopes can be inserted into various orifices to obtain actionable information about what’s going on.

But what about, err, going? Urine flow can be an important leading indicator for a host of diseases and conditions, but it generally relies on subjective reports from the patient. Is there a way to objectively measure how well urine is flowing? Of course there is.

The goal for [GreenEyedExplorer]’s simple uroflowmeter is simple: provide a cheap, easy to use instrument that any patient can use to quantify the rate of urine flow while voiding. Now, we know what you’re thinking — isn’t liquid flow usually measured in a closed system with a paddlewheel or something extending into the stream? Wouldn’t such a device for urine flow either be invasive or messy, or both? Rest assured, this technique is simple and tidy. A small load cell is attached to an ESP8266 through an HX711 load cell amp. A small pan on the load cell receives urine while voiding, and the force of the urine striking the pan is assessed by the software. Reports can be printed to share with your doctor, and records are kept to see how flow changes over time.

All kidding aside, this could be an important diagnostic tool, and at 10€ to build, it empowers anyone to take charge of their health. And since [GreenEyedExplorer] is actually a urologist, we’re taking this one seriously.

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Thermoelectric Generator Shines Where The Sun Doesn’t

March 31, 2018 by 81 Comments

For off-grid renewable electricity, solar seems to make sense. Just throw some PV panels on the roof and you’re all set to stick it to the man, right? But the dirty little secret of the king of clean energy is that very few places on the planet get the sort of sunshine needed to make residential PV panels worth their installation cost in the short term, and the long-term value proposition isn’t very good either.

The drearier places on the planet might benefit from this high-power thermoelectric generator (TEG) developed and tested by [TegwynTwmffat] for use on a wood burning stove. The TEG modules [Tegwyn] used are commercially available and rated at 14.4 volts and 20 watts each. He wisely started his experiments with a single module; the video below shows the development of that prototype. The bulk of the work with TEGs is keeping the cold side of the module at a low enough temperature for decent performance, since the modules work better the higher the difference in temperature is across the module. A finned heatsink and a fan wouldn’t cut it for this application, so a water-cooled block was built to pump away the heat. A successful test led to scaling the generator up to 10 modules with a very impressive heatsink, which produced about 120 watts. Pretty good, but we wonder if some easy gains in performance would have come from using heat sink compound on the module surfaces.

Using thermal differences to generate electricity is nothing new, but a twist on the technique is getting attention lately as a potential clean energy source. And who knows? Maybe [TegwynTwmffat]’s or one of the other Hackaday Prize 2018 entries will break new ground and change the world. What’s your big idea?

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Simple Decoder Serves As Solo Ham’s Test Buddy

March 31, 2018 by 11 Comments

For a hobby that’s ostensibly all about reaching out to touch someone, ham radio can often be a lonely activity. Lots of hams build and experiment with radio gear much more than they’re actually on the air, improving their equipment iteratively. The build-test-tweak-repeat cycle can get a little tedious, though, especially when you’re trying to assess signal strength and range and can’t find anyone to give you a report.

To close the loop on field testing, [WhiskeyTangoHotel] threw together a simple ham radio field confirmation unit that’s pretty slick. It relies on the fact that almost every ham radio designed for field use incorporates a DTMF encoder in the microphone or in the transceiver itself. Hams have used Touch Tones for in-band signaling control of their repeaters for decades, and even as newer digital control methods have been introduced, good old analog DTMF hangs in there. The device consists of a DTMF decoder attached to the headphone jack of a cheap handy talkie. When a DTMF tone is received, a NodeMCU connected to the decoder calls an IFTTT job to echo the key to [WTH]’s phone as an SMS message. That makes it easy to drive around and test whether his mobile rig is getting out. And since the receiver side is so portable, there’s a lot of flexibility in how tests can be arranged.

On the fence about ham as a hobby? We don’t blame you. But fun projects like this are the perfect excuse to go get licensed and start experimenting.

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