SprayPrinter Paints Your Wall, One Pixel At A Time

SprayPrinter is a neat idea. You download a cellphone app, point the camera at a wall, and sweep the wall with a spray can fitted with a (Bluetooth? WiFi?) remote-controlled valve. The phone knows where the nozzle is, and sprays a dot whenever it needs to “paint” the picture of your choosing on the wall.

sprayprinter-estonia-designboom-002-818x500While we’re not sure that we have the patience to paint our walls this way, it’s a cool effect. But even more, we love the idea of using the cellphone camera for location sensing. Many robotics applications do just this with an overhead camera.

Of course, we’d love more detail about how it’s done, but it’s not hard to guess that it’s either a bit of machine vision in the phone, or simpler still, that the spray-can housing has IR LEDs inside that the phone can lock onto. Indeed, the prototype version of the product shown here does look like it has an LED on the opposite side from the orange nozzle.

It wouldn’t be hard to take this to the next level, by adding enough IR LEDs that the camera in your phone can sense orientation as well as location. Heck, by measuring the distances between LEDs, you could probably even get a rough measure of depth. This could open up the use of different nozzles.

Thanks [Itay] for the tip! Some images courtesy SprayPrinter, via designboom.


Crowdfunding Follies: Proof That Ohm’s Law Is Arcane Knowledge

This is a cell phone case that can recharge a cellphone using energy captured from its own radio. It’s been featured on dozens of tech blogs, wowed judges at TechCrunch Disrupt, and it’s a Kickstarter Staff Pick. It’s also proof that nearly everyone in the media who claims any knowledge of technology has no idea behind the foundational properties of technology.

What it is

The Nikola Phone Case from Nikola Labs is a very special phone case for the iPhone 6 and Samsung Galaxy S6. The claims behind this cell phone case state it will recharge your battery by capturing radio energy put out by the cell phone itself. This means capturing RF from the WiFi and cellular transmitters. This captured energy is then converted into something that can recharge the phone, is sent to the USB or Lightning port, and – theoretically – the cycle of electrons turning into photons begins again.

Why it’s crap

Astonishingly, this is not a perpetual motion machine, a device that is completely impractical, or an outright fraud. It’s deceptively correct when it comes to the physics of this device, and as always implementation is everything.

Inside each Nikola Phone Case is a small antenna, boost converter, and circuitry to capture the RF energy coming from the phone. This phone case will actually harvest RF energy, but it will never be able to extend the life of the phone’s battery. Nikola Labs claims their phone case will recover 30% of a battery’s life by harvesting RF energy and using that energy to recharge the phone. However, the energy for this RF energy harvesting scheme comes from the phone itself. The captured energy that would – ideally – end up at a cell phone tower or WiFi router will disappear into this cell phone case. This results in both a dramatic decrease in reception and most likely an increase in power draw due to the phone increasing its transmit power.

To Nikola Labs’ credit, the FAQ on their Kickstarter does address concerns that a phone’s transmitter and antenna may be affected:

The device may change the impedance and overall pattern slightly. We are performing detail characterization of these changes, if any.

Nikola Labs has not performed due diligence on their design. There is a method that will report the RSSI of the cellular radio in an Android phone. Any competent engineer would, upon first seeing this device, figure out if signal strength is affected. This can be done in a few dozen lines of Java. It can be done in under an hour by someone who has never programmed an Android device. Nikola Labs does not provide a comparison of the signal strength of a phone both with and without their case. This is evidence of incompetence, if not malice.

Simply by definition, any device that captures RF energy will ‘shadow’ the transmission. Just like putting a solar panel in front of a flashlight, energy will be captured, but the overall light output of the flashlight and solar panel system will decrease. Nikola Labs has an answer to that:

The device harvests the RF energy around the phone, which is usually absorbed by the hand holding the phone.

It is true that the human body will absorb RF coming out of a phone. WiFi works on the same frequencies as a microwave oven, and defrosting a piece of chicken in a microwave isn’t that much different from grabbing an antenna on a router. Lower powers and different geometries aside, you are right now absorbing microwaves from a WiFi router.

The best way of understanding why simply holding a phone isn’t a very big deal is coming at it from the direction of designing a smart phone. One of the biggest drivers behind the design of a cell phone is how long it will last on a single charge. You can design a phone with a powerful CPU and a huge screen, but the battery won’t last long. Likewise, the engineers that design cell phones will put the antennas in an out of the way place, where they won’t be absorbed by the human body. The Nikola Labs case destroys the engineering decisions inside each cell phone. Think about it; if power was wasted inside a cell phone, wouldn’t engineers at Apple and Samsung work to reduce that waste?

Why everything else is crap, too

There is simply no excuse why hundreds of people would give tens of thousands of dollars to a company that makes outrageous claims with zero evidence. One could attribute this to the public’s severe lack of understanding when dealing with electricity or radio. This, in my opinion, is far too kind.

Nikola Labs’ Kickstarter would not exist without the help of Kickstarter itself and members of the tech media. We first heard of Nikola Labs at TechCrunch Disrupt, where four judges could not find anything wrong with this technology. The presentation at Disrupt went on to be covered by Engadget and a flurry of other tech blogs. Now, dozens of other tech blogs have reported on this Kickstarter, and Kickstarter itself has named it a Staff Pick.

Yes, there are stupid people out there. There are people who will throw money at anything. There are also people who will Barnum up the place sell snake oil to rubes. The fact that Kickstarter would endorse something without a technical assessment defies belief. The only conceivable reason this could be a Staff Pick on Kickstarter is because Kickstarter believes it will be funded, thus earning them a percentage of gross.

This is the end of capitalism, folks. No longer do you need to innovate and make a better mouse trap. All you need to do is convince enough people that you’ve made a better mouse trap.

Covert Remote Protest Transmitters

As a piece of protest art, “Covert Remote Protest Transmitters” ticks all the boxes. An outdoor covert projector that displayed anti-globalization messages at a G20 summit is protest. To disguise it inside a surveillance camera body housing — sticking it to the man from inside one of his own tools — is art. And a nice hack.

However you feel about the politics of globalization (and frankly, we’re stoked to be able to get cheap tech from anywhere in the world) the open-source DIY guidebook to building the rig (PDF) makes up for it all.

They installed the camera/projector long before the summit, where it sat dormant on a wall. A cell phone inside turned on the projector’s light with each ring because they attached a relay to the cell phone’s speaker circuit. In the instructions there’s an example of using a light-dependent resistor (CdS cell) to do the same thing, relying on the phone’s backlight functionality instead. There are a lot of ways to go here.

The optics consist of a couple of lenses aligned by trial and error, then fixed in place to a balsa wood frame with hot glue. A big fat Cree LED and driver provide the photons.

The video documentation of the piece is great. It’s mostly the news media reacting to the art piece as a “security breach”. A security breach would be a gun or a bomb. This was an overhead projector displaying messages that were out of the organizers’ control. Equating security with the supression of dissent is double-plus-ungood. Touché, CRPT.

Anyway, while you’re getting prepped for your next protest, have a look at the Image Fulgurator.

The 2G Raspberry Pi Smartphone

For [Tyler]’s entry to the Hackaday Prize, he’s making something that just a few years ago would be unheard of in a homebrew build. He’s making a DIY smartphone. Yes, with cheap single-board Linux computers, GSM modules, and SPI touchscreen displays, it’s possible to build your own smartphone.

Inside [Tyler]’s DIY smartphone is a Raspberry Pi Model A, a 3.5 inch touchscreen PiTFT with 480×320 resolution, and an Adafruit FONA module The connections are simple enough; the TFT is connected over SPI, and the GSM module over serial. The entire device is powered by a 1200mAh LiIon battery, charged with a powerboost board, runs an operating system written in Python capable of making calls, sending texts, and takes pictures with a Pi camera.

This is not what you would normally call a smartphone. The FONA module is 2G only, meaning you’re limited to 2G speeds and 2G networks. AT&T will be shutting down 2G networks in a little bit, although T-Mobile will be keeping them up for anyone who still has an old Nokia Brick.

That said, [Tyler]’s phone is still exactly what you want in a minimal phone: it just makes calls and receives texts, it has a camera, and unlike the Nokia, you can take it apart and repair it easily. Not that you ever had to do that with a Nokia…

Hackaday Links: January 11, 2015

Listening tests reveal significant sound quality differences between various digital music storage technologies. Finally the audiophile press is tackling the important questions. This listening test looks at the difference between two four-bay NAS boxes, with one making the piano on Scherzo and Trio from Penguin Café Orchestra’s Union Cafe sound more Steinway-like, while another NAS makes it sound more like a Bosendörfer. Yes, your choice of digital storage medium can change the timbre of a piano. Another gem: “Additionally, the two units also had different processor architectures, which might also affect perceived audible differences.” There must be a corollary to Poe’s Law when it comes to audiophiles…

[10p6] has begun a project that can play every old Atari cartridge. Right now it’s just a few bits of plastic that fits every non-Jaguar Atari cartridge, but it’s a start.

The Android IMSI-Catcher Detector. You’ve heard about Stingrays, devices used by law enforcement that are basically fake cell towers. These Stingrays downgrade or disable the encryption present in all cellphones, allowing anyone, with or without a warrant, to listen in on any cell phone conversation. Now there’s an effort to detect these Stingrays. It’s open source, and they’re looking for volunteers.

[Rob] sent in something that’s the perfect application of projection mapping. It’s called Face Hacking, and it’s pretty much just a motion capture systems, a few projectors, a whole lot of CG work, and just a tiny bit of dubstep. It look cool, but we’re wondering what the applications would be. Theatre or some sort of performance art is the best I can come up with.

A while ago, [4ndreas] saw a 3D printed industrial robot arm. He contacted the guy for the files, but nothing came of that. [4ndreas] did what anyone should do – made his own 3D printable industrial robot arm. The main motors are NEMA 17, and printing this will take a long time. Still, it looks really, really cool.

Call A Cell Phone, Find A Tent

relay Finding your tent at a music festival is a tricky endeavor – not only are there miles and miles of tents exactly like yours, you most likely have a few beers or other substances in you that affect your sense of space and/or time.  [James] came up with a great solution to finding your tent by illuminating it with Christmas lights and a cell phone.

The basic idea of [James]’ build is having Christmas light flicker whenever he calls a phone. One feature in nearly every phone that can be exploited to accomplish this task is the backlight turning on when a call is received. Add a phototransistor, a little bit of circuitry, and some Christmas lights, and you have a fully functioning tent finder.

[James]’ circuit is a simple relay driving the Christmas lights, triggered by a phone right on top of the phototransistor. It’s a simple circuit that can be built on a piece of veroboard, and with a few pieces of plastic forming the enclosure, provides a reasonably bulletproof device that will survive the rigors of a music festival. As a bonus, there’s no need to modify the phone to trigger a remote circuit. Video of the device in action below.

Continue reading “Call A Cell Phone, Find A Tent”

Phoenard: Arduino Phone as Small as An Arduino Mega


Hanging out at one side of the Atmel booth at Maker Faire was [Pamungkas Sumasta] who was showing off his Arduino cellphone called Phoenard. We really like the form-factor but its hackability is where it really shines. [Sumasta] showed off the menu system which is quite snappy and makes it simple for you to add your own applications. Software isn’t the only thing you can customize, as there’s a connector at the bottom of the phone. He showed off a breadboard attachment which was hosting LEDs of various colors. Their intensity can be altered using a simple slider app on the touchscreen. But there’s more power if want it. Also on exhibit was a self-balancing robot body which has a connector at the top for the phone.

[Sumasta] won the Atmel Hero contest and we assume that’s how he made it all the way to San Francisco from The Netherlands for Maker Faire. You can learn a few more technical details about Phoenard on the Facebook page.