[Igor] wished to upgrade his newly acquired radio — a Baofeng UV-82 — with a larger memory for storing additional scanning channels, and came up with a very elegant solution: Replacing it’s EEPROM with a larger one and injecting the additional memory address bits into the I2C data line.
Today is a very special day for [Mandy and Sebastian], as they conclude the sacred solder joint of marriage. We send our sincerest congratulations and best wishes to the bridal couple, and can’t help but envy the guests of their ceremony, who received a very special wedding favor: A WeddingBot.
For their wedding party, [Mandy and Sebastian] created a little game on their own (translated). Each guest would receive a unique, little WeddingBot. Each of these is individually tailored for a certain guest and features a fitting look, a characteristic behavior and would play a special melody or jingle meaningful to this guest. However, the guests don’t get their WeddingBot, they get the WeddingBot of another guest – and the challenge to find this guest on the party. Guests would then exchange their WeddingBots, which also makes a great occasion to introduce themselves to each other. If the clues given by the WeddingBots themselves would not suffice to find the right owner, guest could place a WeddingBot on a clue station, which then would provide further hints by displaying images, texts or even riddles.
The design is based on the ATtiny45 microcontroller, with LEDs for the eyes, a light sensor, and a piezo disc for the sound as the main components. As an enclosure, they chose to repurpose empty Nespresso® capsules, which look nice and adds volume to the PCBs. The smiley face silk screen on the PCBs was then individualized with a black marker and packed in a beautiful hand-crafted box. The little fellows communicate with the Raspberry Pi based clue station by flashing their LEDs in a certain pattern. A light sensor hooked up to the Pi lets the station identify the bot and display the corresponding clue on a screen. Check out the video below to see how it works:
It’s not just an LED-blinker, though. He added in a light-detection function so that it only switches on at night. It uses the Forest Mims trick of reverse-biasing the LED and waiting for it to discharge its internal capacitance. The point is, however, that it gives the chip something to do instead of simply sleeping.
Although he’s an AVR user by habit, [Thierry] finds in favor of the PIC because it’s got a lower power draw both when idling and when awake and doing some computation. This is largely because the PIC has an onboard low-power oscillator that lets it limp along at 32 kHz, but also because the chip has a lower power consumption in general. In the end, it’s probably a 10% advantage to the PIC on power.
If you’re competent with one of the two chips, but not the other, his two versions of the same code would be a great way to start familiarizing yourself with the other. We really like his
isDarkerThan() function which makes extensive use of sleep modes on both chips during the LED’s discharge period. And honestly, at this level the code for the two is more similar than different.
(Oh, and did you notice [Thierry]’s use of a paper clip as a coin-cell holder? It’s a hack!)
Surprisingly, we’ve managed to avoid taking a stray bullet from the crossfire that occasionally breaks out between the PIC and AVR fans. We have covered a “shootout” before, and PIC won that round too, although it was similarly close. Will the Microchip purchase of Atmel calm the flames? Let’s find out in the comment section. We have our popcorn ready!
If you’re a long-time Hackaday reader like we are, you’ll certainly remember a rash of projects from around ten years ago that all (mis-)used an LED as a light sensor. The idea wasn’t new, but somehow it made the rounds and insinuated itself into our collective minds. Around the same time, a cryptographic cipher with an exceptionally small memory footprint was also showing up in hacker projects: TEA (Tiny Encryption Algorithm).
This old project by [Marcin Bojanczyk], [Chris Danis], and [Brian Rogan] combines both the LED-as-light-sensor meme and TEA to make a door-entry keyfob that works over visible light. And they do so using almost nothing — a few LEDs and just over 2Kb of code. It’s pretty sweet.
Which brings us to the question: where are they (LED-sensors and TEA) now?
LED-as-light-sensor was just cool. We certainly loved the idea back in 2006. But [Forrest Mims] had been using the phenomenon for decades back then. It certainly makes sense when you’re trying to squeeze as much as possible out of as little as possible, or when budget is a main concern and you just can’t afford an extra photodiode.
But our own experience with LEDs as light sensors is that the results are extremely variable across different LEDs. Code that works with water-clear red LEDs might not work with the ones that come in red-tinted plastic, for instance. Is that why they went extinct?
Similarly, the TEA family of ciphers showed up in a bunch of projects around this time, from the badge for the HOPE conference in 2010 to a widely used RFM12B radio library. There are a couple of attacks on XXTEA, but they only affect reduced-round versions of the cipher, and rely on a tremendous amount of intercepted data — more than we’d see in a home-automation network over years.
Over the last five years or so, there’s been a lot more Internet of Things, which means using standard Internet-style encryption methods (AES and so on) that are widespread on non-memory-constrained computers. Is that what happened to XXTEA?
Anyway, we got tipped off to a project that combined a few of our favorite (old) ideas in one, so we thought that we’d share. Thanks [Blue Smoke] for the walk down memory lane. Any of you out there keeping the flame(s) alive? Have you used sensing LEDs or XXTEA? Are those projects still going, or do you have any future projects planned with these tricks still up your sleeve? Let us know in the comments below.
[Alex] is no stranger to making machines of negligible utility. A few years ago he made the Almost Useless Machine, a solar-powered system that cuts through a 20mm dowel rod while you wait (and wait, and wait). Enamored by the internet’s bevy of powered hacksaws, he sought to build a sturdier version that’s a little more useful. Approximately five months of free time later, he had the Almost Useful Machine.
It runs on a wiper motor and a recycled power supply from a notebook computer. [Alex] rolled his own board for controlling the motor with an ATtiny25. The circuit turns potentiometer movement into PWM, which controls the motor through a MOSFET. After the cut is finished, an endstop microswitch immediately cuts the motor.
Every bit of the chassis is aluminum that [Alex] machined by hand. Don’t have that kind of setup? How about a powered hacksaw with a 3D-printed linkage? Make the jump to see it in action, and stick around for the two-part time-lapse build video.
[ANTALIFE] is going to tie the knot sometime in 2017. Instead of sending out paper announcements or just updating his Facebook status, he wanted to give their family members something lasting and memorable, like a small trinket with a pair of light-up cats.
This project is pretty simple in theory. A pair of RGB LEDs cycle through the colors of the rainbow with the help of an ATtiny25 and resistors carefully chosen for each LED. But there are several challenges at play here. [ANTALIFE] wanted to design something quite small that would last at least a day on a single CR2032 coin cell. This project was his first foray into SMD/SMT design and construction. We think that this warrants its own congratulations, especially since it looks as though he made at least a dozen of these things.
[ANTALIFE] made things much easier for himself with the purchase of a cheap hot air rework station and used a chip clip to program the ‘tiny. The cats are a design from Thingiverse, which he modified to turn them into bride and groom. Watch a whole line of them glow after the break. We sincerely hope that a larger version of these cats end up on top of the wedding cake.
The Raspberry Pi was made to be inexpensive with an eye toward putting them into schools. But what about programs targeted at teaching embedded programming? There are plenty of fiscally-starved schools all over the world, and it isn’t uncommon for teachers to buy supplies out of their own pockets. What could you do with a board that cost just one dollar?
That’s the idea behind the team promoting the “One Dollar Board” (we don’t know why they didn’t call it a buck board). The idea is to produce a Creative Commons design for a simple microcontroller board that only costs a dollar. You can see a video about the project, below.