An attempt to replace multiple RFID cards with a single hacked-together tag


It’s kind of a convoluted title, but [Hudson's] attempt to replace multiple HID Prox cards with one AVR chip didn’t fully pan out. The project started when he wanted to reduce the number of RFID access cards he carries for work down to just one. The cards use the HID Proximity protocol which is just a bit different from the protocols used in most of the hobby RFID projects we see. He ended up taking an AVR assembly file that worked with a different protocol and edited it for his needs.

The device above is the complete replacement tag [Hudson] used. It’s just an AVR ATtiny85 and a coil made of enameled wire. The coil pics up current from the card reader’s magnetic field, and powers the chip through the leakage on the input pins (we’ve seen this trick a few times before). The idea he had was to store multiple codes on the device and send them all in a row. He was able to get the tag to work for just one code, but the particulars of the HID Prox reader make it difficult if not impossible to send multiple codes. The card must send the same code twice in a row, then be removed from the magnetic field before the reader will poll for another combination.

Communication protocol for an indoor helicopter


There’s a special type of satisfaction that comes from really understanding how something works at the end of a reverse engineering project. This grid above is the culmination of [Spencer's] effort to reverse engineer the IR protocol of a Propel ExecuHeli indoor helicopter toy.

The first thing he looked at was the three different controller channels which can be selected to allow multiple helicopters to be used in the same area. [Spencer] was surprised that they all used the same carrier frequency. The secret must be in the coded packets so his next challenge was to figure out how the data was being transmitted via the Infrared signal. It turns out the packets are using pulse-length coding (we were unfamiliar with this protocol but you can read a bit more about it here). The last piece of the puzzle was to capture packets produced by each unique change of the control module. With each bit (except for bit 11) accounted for he can now format his own codes for a controller replacement. Perhaps he’s looking to make the helicopter autonomous?

Brute force finds the lost password for an electronic safe


[Teatree] tells a sad, sad story about the lost password for his fire safe. The electronic keypad comes with a manufacturer’s code as well as a user selected combination. Somehow he managed to lose both of them, despite storing the user manual safely and sending the passwords to himself via email. He didn’t want to destroy the safe to get it open, and turning to the manufacturer for help seemed like a cop-out. But he did manage to recover the password by brute forcing the electronic keypad.

There is built-in brute force protection, but it has one major flaw. The system works by enforcing a two-minute lockout if a password is entered incorrectly three times in a row. But you can get around this by cutting the power. [Teatree] soldered a relay to each set of keypad contacts, and another to the power line and got to work writing some code so that his Arduino could start trying every possible combination. He even coded a system to send him email updates. Just six days of constant attacking netted him the proper password.

Land speed baby carriage record set at 53 mpg


Let’s face it, you’ll never break the motorcycle land speed record without a stellar engineering team and some serious corporate sponsorship. But this build proves that individuals can still set other speed records. [Colin Furze] rode his motorized baby carriage over the 53 mile per hour mark to set a the world’s record. We were surprised to learn it only took him about one month and $750 to build the infant death machine.

The design appears to take a page from the commercial lawnmower industry. We say that because the driver rides along on a little tow dolly behind the carriage itself. All of the controls are mounted within easy reach of the T-bar steering mechanism. There are a couple of rockers for his thumbs which actuate the gas and brakes. Red push buttons just below the handlebars are used for up and down shifting with a third button used as a kill switch. The only thing missing from the write up is video footage of the actual 53mph run. We guess you’ll just have to take his word for it.

[via Dvice]

Laminated wooden case brings a dropped coffee grinder back from the junk heap


Instead of giving it up for dead, [Suprise Pink Mist] fabricated a replacement case for the motor and blade of his broken coffee grinder. The original enclosure was made of plastic, which didn’t survive being dropped. There isn’t an image of what those plastic parts looked like, but we have to think they were nowhere near as neat as the replacement.

The first step was to cut a set of plywood discs to the approximate outside dimensions. Since the base of the motor has several different diameters each disc had a void cut out of its center to match. The image to the right shows the motor sitting upside down next to the stacked plywood. The black electrical tape seals around the mason jar ring which was a perfect friction fit with the original bowl of the grinder. Once everything was glued together the outside edges were flattened on a belt sander and the mason jar was screwed in place to house the beans during grinding.

[via Reddit]

Award clock put to good use as a bench meter


The motivation industry turns out these type of award trinkets by the millions. Here’s a way to actually put the thing to use. Instead of displaying time, the clock dial serves as the readout of a voltage meter.

When we first saw this post we assumed that the hack used some type of coil injection to drive the hands. But it turns out that this is mechanically driven. The image above shows the stepper motor which is mounted behind the clock. Its drive shaft is coupled with the adjustment knob on the back of the clock. The precision of the motor lets the PICAXE set the clock dial based on the number of motor steps. The hour hand shows the tens value with the minutes serving as ones (base 10, not base 60). This means the top measurable voltage is 12V — when the hour hand is at 12 the measurement is 0 volts plus tenths of a volt from the minute hand. With the dial taken care of the rest of the project focuses on measuring the voltage using the ADC, which has an upper limit of just 5V. This is overcome with a simple voltage divider.

After the break you can see the accuracy of the rig as it performs measurements next to a digital voltmeter.

[Read more...]

Building a tool to bend small metal tubes


[Joel] is setting up a really nice workshop. Included in his list of machinery are the staples of any workshop; a lathe, miter saw, containers full of organized screws, and a manual mill converted to a CNC machine. [Joel] wanted an oiling system for his mill, and like any good maker decided to fabricate his own. This required bending very small diameter brass tubes, something doable by hand (or without sand, at least). He decided to solve this problem with a DIY tube bending tool that allows him to bend tiny brass tubing without the walls collapsing.

[Joel] broke out his lathe and machined two brass rollers with a groove to hold his 3/16″ tubing. One of these brass rollers is attached to a handle, while the other is attached to a block that gets clamped into [Joel]‘s bench vise. After threading some tubing through the rollers, [Joel] is able to bend it precisely with only a tiny bit of collapsing on small-radius bends.