Good Vibrations: Giving The HC-SR04 A Brain Transplant

March 17, 2014 by 23 Comments

[Emil] got his hands on a dozen HC-SR04 ultrasonic sensors, but wasn’t too happy with their performance. Rather than give up, he reverse engineered the sensor and built an improved version. Hackers, Makers, and robotics enthusiasts have had easy access to standard sonar platforms since the early 1980’s, when Polaroid began selling their 6500 sonar modules. A number of companies have released sonar boards since then, notably The Parallax Ping))) module. The HC-SR04 appeared on the market a few years back as a low-cost alternative of the Ping.

[Emil] found that the HC-SR04 would work reliably on hard surfaces as far as 4 meters away from the sensor. However, he got a lot of bad data back when using soft sided targets, or when no target was present at all.  [Emil] reverse engineered the schematic of the HC-SR04 and found some interesting design decisions. A Max232 RS-232 converter chip is used for its +-12V +-10V charge pumps. The charge pumps are connected to create 24V 20V at the ultrasonic transmitter. A mask programmed microcontroller manages the entire unit, commanding the ultrasonic transmitter to send 40Khz pulses, and listening for returns on the receive side of the system. [Emil] believes the micro is running in polled mode, due to the fact that it sometimes misses pulses. Even worse, the micro runs on an unmarked 27MHz crystal which had quite a bit of drift.

[Emil] solved these problems by creating his own PCB with an ATtiny24 and a 12MHz crystal. He increased the pin count from 4 to 6, allowing the ATtiny to be programmed in circuit, as well as opening the door to I2C and SPI operation. To build the boards up, [Emil] first solders his micro and crystal. He then uses a hot air gun to move all the components from the HC-SR04 board to his own. The new boards are still being tested, but [Emil] has posted his PCB and BOM data. He’s also promised to post his AVR code when it is available.

MRRF: Stuff From Lulzbot

March 17, 2014 by 8 Comments

A lot of the big names in 3D printers were at the Midwest RepRap festival showing off their wares, and one of the biggest was Lulzbot with their fabulous Taz 3 printer. This year, they were showing off a new filament, a new extruder, and tipping us off to a very cool project they’re working on.

The new products Lulzbot is carrying are Ninjaflex filament and the extruder to go with it. Ninjaflex is the stretchiest filament we’ve ever seen, with the feel of a slightly hard silicone rubber. Straight off the spool, the filament will stretch to a little less than twice its original length, and in solid, printed form its a hard yet squishy material that would be perfect for remote control tank treads, toys, and 3D printed resin molds. With all the abuse the sample parts received over the weekend, we’re going to call Ninjaflex effectively indestructible, so long as you don’t try to pull the layers apart.

Also from Lulzbot is word on the new 3D scanner they’re working on. The hardware isn’t finalized yet, but the future device will use a webcam, laser, and turntable to scan an object and turn it directly into an .STL file. Yes, that means there won’t be any point clouds or messing about with Meshlab. Lulzperson [Aeva] is working on the software that subtracts an object from its background and turns it into voxels. The scanner will be low-cost and open source, meaning no matter what the volume of the scanner will be, someone will eventually build a person-sized 3D scanner with the same software.

Videos of [Aeva] below showing off the new stuff and talking about the scanner.

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Hacking The Sci-Fi Contest Team Requirement

March 17, 2014 by 7 Comments

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We saw that some readers were not entirely happy with the team requirement for our Sci-Fi contest, which is running right now. We figured that those who do not work well with others might commit a bit of fraud to get around the requirement. But we’re delighted that someone found a much more creative solution. Why not enlist an AI to collaborate on your project?

[Colabot] is a hacker profile over on hackaday.io which is driven by ELIZA, a computer program that achieves limited interaction through natural language. Supposedly you add [Colabot] to your project and as it questions. We asked one on the profile page and are still awaiting the response. We think this itself could be a qualifying entry for the Sci-Fi contest if someone can find the right thematic spin to put on it.

As far as contest entries go there are only seven so far. Since everyone who submits an entry gets a T-shirt, and there are 15 total prize packages, we encourage you to post your entry as soon as possible. We want to see teams from hackerspaces and we can cryptically tell you that good things come to teams who post their project with the “sci-fi-contest” tag early!

Radar Imaging In Your Garage: Synthetic Aperture Radar

March 17, 2014 by 48 Comments

Learn why you were pulled over, quantify the stealthiness of your favorite model aircraft, or see what various household items look like at 10 GHz. In this post we will describe the basics of Synthetic Aperture Radar (SAR) imaging, beginning with a historical perspective, showing the state of the art, and describing what can be done in your garage laboratory. Lets image with microwaves!

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NFC Ring Unlocks Your Phone

March 17, 2014 by 31 Comments

NFC Ring

This little ring packs the guts of an NFC keyfob, allowing [Joe] to unlock his phone with a touch of his finger.

The NFC Ring was inspired by a Kickstarter project for a similar device. [Joe] backed that project, but then decided to build his own version. He took apart an NFC keyfob and desoldered the coil used for communication and power. Next, he wrapped a new coil around a tube that was matched to his ring size. With this assembly completed, epoxy was used to cast the ring shape.

After cutting the ring to size, and quite a bit of polishing, [Joe] ended up with a geeky piece of jewelry that’s actually functional. To take care of NFC unlocking, he installed NFC LockScreenOff. It uses Xposed, so a rooted Android device is required.

We’ll have to wait to see how [Joe]’s homemade solution compares to his Kickstarter ring. Until then, you can watch a quick video of unlocking a phone with the ring after the break.

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MRRF: ARM-Based CNC Controllers

March 17, 2014 by 23 Comments

 

8-bit microcontrollers are the standard for RepRap electronics, but eventually something better must come along. There has been a great deal of progress with ARM-based solutions, and of course a few of these made a showing at the Midwest RepRap Festival.

First up is [Mark Cooper], creator of Smoothieboard, the ultimate RepRap and CNC controller. It’s an ARM Cortex-M3 microcontroller with Ethernet, SD card, and up to five stepper drivers. It had a Kickstarter late last year and has just finished shipping all the rewards to the backers. In our video interview, [Mark] goes over the functions of Smoothieboard and tells us about some upcoming projects: the upcoming Smoothiepanel will feature a graphic LCD, SD card, rotary encoder and buttons, all controlled over USB by the Smoothieboard.

Next up is [Charles] with a whole bunch of CNC capes for the Beaglebone. By far the most impressive board was a huge I/O expander, motor driver, and everything controller for a Beaglebone featuring – get this – three parallel port interfaces. This was a one-off board costing thousands of dollars, but [Charles] did show off a few smaller and more practical boards for Beaglebone CNC control. Here’s a link to [Charles]’ capes.

Videos below.

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Hacking Rolling Code Keyfobs

March 17, 2014 by 39 Comments

Most keyfobs out there that open cars, garage doors, and gates use a rolling code for security. This works by transmitting a different key every time you press the button. If the keys line up, the signal is considered legitimate and the door opens.

[Spencer] took a look into hacking rolling code keyfobs using low cost software-defined radio equipment. There’s two pars of this attack. The first involves jamming the frequency the keyfob transmits on while recording using a RTL-SDR dongle. The jamming signal prevents the receiver from acknowledging the request, but it can be filtered out using GNU Radio to recover the key.

Since the receiver hasn’t seen this key yet, it will still be valid. By replaying the key, the receiver can be tricked. To pull off the replay, GNU Radio was used to demodulate the amplitude shift keying (ASK) signal used by the transmitter. This was played out of a computer sound card into a ASK transmitter module, which sent out a valid key.