Update: Testing The Accuracy Of A Magnetic Rotary Encoder

A while back we featured a magnetic rotary encoder that [LongHairedHacker] designed. The heart of the system is an AS5043 magnetic rotary sensor which runs from $6.5-$11 and has a 10 bits precision. As we wanted to check if his design was really efficient, he made a test bench for it.

For 360 degrees, a 10 bits precision means a ±0.175º accuracy, which is quite impossible to check with conventional measurement equipment. The first approach he thought of was to attach a mirror to the encoders axis and point a laser beam at it. The laser beam would be reflected across the room to a big scale, but the minimum required distance would have been 5 meters (16 feet). So he preferred attaching a motor to the sensor, rotating at a given speed and measuring the sensor output.

In the first part of his write-up, [LongHairedHacker] lays the math which explains the different kinds of errors that should be expected from his setup and sensor. He then proceeds with his test, where an ATMEGA8 based board is used to send the measured position to his computer. It should be noted that [LongHairedHacker] currently uses the time spent between two received measurements on his computer as a time base, but he is planning on time stamping the data on his board in the next future. Nevertheless, he managed to measure an average ±0.179º accuracy with his simple test bench, which is very close to the manufacturer specification.

Here is the link to our original post about his sensor.

Fix A Keyboard’s Firmware With Trial, Error, And I2C

eepromKeyboardFlash

If the media shortcut keys on your keyboard don’t function correctly due to outdated firmware, the manufacturer may recommend you ship it to them for an update. [Alvaro] didn’t care to wait that long, so he cracked it open and taught himself how to mod the EEPROM. The result is a well-documented breakdown of sorting out the keyboard’s guts. Inside he finds a USB hub, which he ignores, and the keyboard controller chip, which he attacks. Two data sheets and a schematic later, [Alvaro] breaks out the logic analyzer to compare physical key presses to the keypad codes they output.

He dumps the entire EEPROM and follows up with a quick flash via I2C to change the “next song” key to instead output the letter “a”. That seems to work, so [Alvaro] combs through an HID USB usage table for some codes and has to guess which ones will properly control Spotify. He converts the media keys from “scan next” and “scan previous” to “rewind” and “fast forward.” Problem solved.

[Alvaro] had zero knowledge of keyboards prior to opening this one up. If you aren’t already taking things apart to see how they function and how to fix them, hopefully his success will persuade you to explore and learn about those “black boxes” in your home. And, if you’ve never used I2C before—or think it might be the name of a boy band—head over to [Kevin’s] tutorial on bitbanging I2C by hand.

Getting Boxeebox Root And Making It Useful Again

When it was released just three years ago, the Boxee Box – a set-top box designed to run the Boxee HTPC environment – was a pretty cool little device. Even though it was somewhat crippled from the get-go, the Boxee Box had a lot of neat features including a remote with a QWERTY keyboard, the ability to stream media over a home network, and automatic scraping of IMDB for proper info for all your torrented media. Team Boxee recently left for Samsung, and the severs have been shut down, but that doesn’t mean your Boxee Box has outlived its usefulness. Here’s a few hacks to get your Boxee Box up and running again, sent in by [Ryan].

Last year at DEFCON 20, [GTVHacker] demonstrated two ways to get root on the original Boxee Box. The first is a software root method that runs a shell script on every boot. The second is a far more elegant hardware modification that involves cutting two traces and soldering wires to a UART adapter.

Root is fine, but what the Boxee Box really needs is an update to its media player. Boxeehack does just this and only requires a USB stick for installation. Boxeehack puts back some of the default XMBC functions that were removed from the Boxee Box, and gives anyone running this media center root.

It may be old and unsupported, but there’s still plenty of life left in the Boxee Box. They’re also pretty cheap, so if you’re looking for a small media player for your TV, you might want to think about picking one of these boxes up.

Reverse-engineering Old Finnish Metro Station Displays

This project definitely was a patience tester. As the control system of the Helsinki metro was (and still is) under big renovation, [Konsta] could buy three old information displays for a very cheap price (5€ each). However, these displays came with no information whatsoever about the way to drive them, thus starting a long reverse-engineering journey.

[Konsta] started by taking one apart, discovering that each side of the display was composed of 10 daisy-chained LCD screens and some kind of control box. As you may have guessed, the key to reverse engineering the display was studying the contents of this box. It turned out that the control electronics were composed of an 8085 CPU, some RAM, a peripheral I/O chip, an UV-erasable EPROM chip (containing 32KB of program memory) and an EEPROM.

[Konsta] used an AVR to dump the memory contents of the two latter chips and it was at this part of the project that the Helsinki Hacklab joined in. Together, they reverse engineered the control PCB, studied the assembler code, sniffed the different on-board buses to fully understand how the display could be controlled.

We strongly recommend reading [Konsta]’s writeup, especially knowing that he made this english page just for us!

Building An Entire Pinball Machine From Just The Playfield

It all started  when [Iancole] bought a Fireball Home edition playfield on some famous auction website for $135. Originally, he had the intent of lighting the lamps with an Arduino, framing it, and hanging it on the wall of his office — which often happens with old pinball parts. But then his boys asked if he “could make it play”.

[Iancole] managed to find the pinball schematics online and started designing the electronics required by the many LEDs, solenoids and switches. As the LEDs and switches are on the same matrix, he chose a simple Arduino to cycle through them, giving the player the impression that the lights are constantly on. [Iancole] originally planned on using his raspberry Pi to control the solenoids, but he later switched to another Arduino because of the precise timing required.

Therefore, his Pi was used as the heart of the machine. It is interfaced to the two Arduinos to read states and send commands while running the game program, displaying HD graphics on a 24″ screen, playing music and game event sounds. All the electronics are proudly displayed on the backbox, and many developments are planned for it. Also, the machine will be on display at the Orlando Mini Maker Faire on October 5th!

Controlling Chromecast: AirCast APK Released

[Koush] is at it again, this time releasing AirCast, an Android app that’ll push videos to the Chromecast from Dropbox, Google Drive, and your phone’s Gallery. Astute Hackaday readers will recall that AirCast has been around for a few weeks now, but limited to only his whitelisted Chromecast. As [Koush] explains it, he had to reverse engineer the protocols and now he simply avoids the Chromecast SDK entirely. If you’re lucky enough to have a Chromecast, you’ll want to hurry and grab the APK (direct download link) and have some fun with it before it self-destructs. [Koush] isn’t ready to release it for more than a 48 hour period, but we encourage you to take advantage of AirCast and contribute to his call for feedback, bugs, and crash reports. You have a little under a day left.

See “AllCast” work its magic in the video below. No, that’s not a typo. Apparently [Koush] has been struggling with available names for the app, and you’ll hear him call it “AllCast” in the Youtube video. That name was taken for some other product, though, and “AirCast” has now replaced it. If you suddenly regret not immediately ordering a Chromecast and are sitting this one out, go read [Mike’s] rant and get psyched up for when they’re back in stock.

Continue reading “Controlling Chromecast: AirCast APK Released”

Adult Sized Baking Powder Submarine

baking-powder-submarine

It really doesn’t matter what age you are, we’re sure you remember baking powder submarines. That’s because cereal manufacturers have been including them as prizes since the advent of injection molded plastic. Fill them with baking soda and take them in the bath with you. They gently dive and surface. The problem is that the cereal prizes were tiny. Now you can relive your childhood with an adult size version of your own making.

The submarine is basically a hunk of PVC with a conning tower to keep it upright and a chunk of hose into which the baking powder is placed. The idea is that the powdery acid and base that makes up the stuff reacts when hit with water. This gives off a bit of carbon dioxide, which makes the sub float to the surface until the bubble escapes and is replaced with water to again sink the ship. The difficult part is to find the right buoyancy (using wine bottle cork) so that the bubble is all it takes to oscillate between the surface and the watery depths.

Watch it go in the video after the break.

Continue reading “Adult Sized Baking Powder Submarine”