Cheap Sensors And An SDR Monitor Conditions In This Filament Drying Farm

September 14, 2019 by Dan Maloney 3 Comments

We don’t know where [Scott M. Baker] calls home, but it must be a pretty humid place indeed. After all, he has invested quite a bit in fancy vacuum storage containers to keep his 3D-printer filament dry, with the result being this sensor-laden filament drying farm.

[Scott] wasn’t content to just use these PrintDry containers without knowing what’s going on inside. After a little cleaning and lube to get all the containers working, he set about building the sensors. He settled on a wireless system, with each container getting a BME280 temperature/humidity/pressure sensor and an SYN115 315-MHz ISM band transmitter module. These go with an ATtiny85 into a compact 3D-printed case holding a little silica desiccant. The transmitters are programmed to comply with ISM-band regulations – no need to run afoul of those rules – while the receiver is just an SDR dongle and a Raspberry Pi running rtl_433. The long-ish video below details design and construction.

The idea behind these vacuum containers would seem to be to pull out humid air and prevent it from coming back in. But as [Scott] quickly learned from his telemetry, following the instructions results in the equivalent atmospheric pressure of only about 2700′ (823 meters) elevation – not exactly a hard vacuum. But as [Scott] points out, it’s enough to get a nice, tight seal, and his numbers show a lowered and constant relative humidity over time.

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Handheld Game Console Puts Processing Power In The Cartridge

July 12, 2019 by Lewin Day 18 Comments

With the proliferation of cheap screens for use with microcontrollers, we’ve seen a matching proliferation in small handheld gaming projects. Pick your favourite chip, grab a screen off the usual suspects, add some buttons and you’re ready to go. [bobricius] has put a unique spin on this, with an unconventional cartridge-based build.

The main body of the handheld is constructed from attractive black and gold PCBs, and features a screen, some controls and an on/off switch. There’s also a microSD socket is on the board, which interfaces with cartridges which carry the microcontroller. Change the cart, and you can change the game.

[bobricius] has developed carts for a variety of common microcontroller platforms, from the Attiny85 to the venerable ATmega328. As the microSD slot is doing little more then sharing pins for the screen and controls, it’s possible to hook up almost any platform to the handheld. There’s even a design for a Raspberry Pi cart, just for fun.

It’s an entertaining take on the microcontroller handheld concept, and we can’t wait to see where it goes next. It reminds us of the Arduboy, which can even do 3D graphics if you really push it. Video after the break.

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Split Flap Clock Keeps Time Thanks To Custom Frequency Converter

June 23, 2019 by Dan Maloney 6 Comments

Why would anyone put as much effort into resurrecting a 1970s split-flap clock as [mitxela] did when he built this custom PLL frequency converter? We’re not sure, but we do like the results.

The clock is a recreation of the prop from the classic 1993 film, Groundhog Day, rigged to play nothing but “I Got You Babe” using the usual sound boards and such. But the interesting part was getting the clock mechanism keeping decent time. Sourced from the US, the clock wanted 120 VAC at 60 Hz rather than the 240 VAC, 50 Hz UK standard. The voltage difference could be easily handled, but the frequency mismatch left the clock running unacceptably slow.

That’s when [mitxela] went all in and designed a custom circuit to convert the 50 Hz mains to 60 Hz. What’s more, he decided to lock his synthesized waveform to the supply current, to take advantage of the long-term frequency control power producers are known for. The write-up goes into great detail about the design of the phase-locked loop (PLL), which uses an ATtiny85 to monitor the rising edge of the mains supply and generate the PWM signal that results in six cycles out for every five cycles in. The result is that the clock keeps decent time now, and he learned a little something too.

If the name [mitxela] seems familiar, it’s probably because we’ve featured many of his awesome builds before. From ludicrous-scale soldering to a thermal printer Polaroid to a Morse-to-USB keyboard, he’s always got something cool going on.

Keeping Birds At Bay With An Automated Spinning Owl

May 30, 2019 by Tom Nardi 3 Comments

There’s nothing wrong with building something just to build it, but there’s something especially satisfying about being able to solve a real-world problem with a piece of gear you’ve designed and fabricated. When all the traditional methods to keep birds from roosting on his mother’s property failed, [MNMakerMan] decided to come up with a more persuasive option: a solar powered spinning owl complete with expandable batons.

We imagine the owl isn’t strictly necessary when you’re whacking the birds with a metal bar to begin with, but it does add a nice touch. Perhaps it will even serve to deter some of the less adventurous birds before they get within clobbering distance, which is probably in their best interest. [MNMakerMan] says the rotation speed of the bars seems low enough that he doesn’t think it will do the birds any physical harm, but it’s still got to be fairly unpleasant.

At first glance you might think that this contraption simply spins when the small 10 watt photovoltaic panel next to it catches the sun, but there’s actually a bit more to it than that. Sure he probably could just have it spin constantly whenever the sun is up, but instead [MNMakerMan] is using a ATtiny85 to control the 11 RPM geared DC motor with a IRF540 MOSFET. By adding a DS3231 RTC module into the mix, he’s able to not only accurately control when the spinner begins and ends its bird-busting shift, but implement timed patterns rather than running it the whole time. All of which can of course be fine-tuned by adjusting a couple variables and reflashing the chip.

We’ve seen plenty of automated systems for keeping cats away, and of course squirrels are a common target for such builds as well, but devices to deter birds are considerably less common among these pages. So it would seem that, at least for now, [MNMakerMan] has the market cornered on solar bird smashing gadgets. We’re sure Mom’s very proud.

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Imitating Art In Life With A Reverse-Engineered Tattoo

March 23, 2019 by Dan Maloney 6 Comments

In general, tattoo artists are not electrical engineers. That’s fine; the world needs both professions. But when you need a circuit designed, you’re better off turning to an EE rather than a tattoo artist. And you certainly don’t want an EE doing your new ink. Disaster lies that way.

Surprisingly, [Missa]’s tattoo of a heart-shaped circuit turned out at least to be plausible design, even if it’s not clear what it’s supposed to do. So her friend [Jeremy Elson] took up the challenge to create a circuit that looked like the tattoo while actually doing something useful. He had to work around the results of tattoo artistic license, like sending traces off to the board’s edge and stranding surface-mount components without any traces. The artist had rendered an 8-pin DIP device, albeit somewhat proportionally challenged, so [Jeremy] went with an ATtiny85, threw on a couple of SMD resistors and a cap, and placed two LEDs for the necessary blinkenlights. Most of the SMDs are fed from traces on the back of the board that resurface through vias, and a small coin cell hidden on the back powers it. One LED blinks “Happy Birthday [Missa]” in Morse, while the other blinks prime numbers from 2 to 23 – we’ll assume this means it was [Missa]’s 23rd birthday.

There’s a surprising amount of crossover between the worlds of electronics and tattooing. We’ve featured functional temporary tattoo circuits, prison-expedient tattoo guns, and even a CNC tattoo machine.

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Get Twelve Charlieplexed PWM Outputs From An ATtiny85

February 24, 2019 by Donald Papp 8 Comments

Most of us are aware that charlieplexing can drive a large number of LEDs from a relatively small number of I/O pins, but [David Johnson-Davies] demonstrates adding another dimension to that method to create individually controlled PWM outputs as well. His ATtiny85 has twelve LEDs, each with individually-set brightness levels, and uses only four of the five I/O pins on the device.

Each LED can be assigned a brightness between 0 (fully off) and 63 (fully on). The PWM is done by using one of the timers in the ATtiny85 to generate a periodic interrupt, and the ISR for the interrupt takes care of setting the necessary ratios of on and off times for each charlieplexed output. The result? Twelve flicker-free LEDs with individually addressable brightness levels, using an 8-pin microcontroller and just a few passive components on a tiny breadboard. There’s even one I/O pin left on the ATtiny85, for accepting commands or reading a sensor.

[David] really wrings a lot out of the ATtiny series of microcontrollers with his compact projects, like his Tiny Function Generator (which recently got an update.) He also demonstrated that while charlieplexing is usually used with LEDs, charlieplexing can be used with switches just as easily.

A Tiny IDE For Your ATtiny

February 8, 2019 by Tom Nardi 23 Comments

When writing code for the ATtiny family of microcontrollers such as a the ATtiny85 or ATtiny10, people usually use one of two methods: they either add support for the chip in the Arduino IDE, or they crack open their text editor of choice and do everything manually. Plus of course there are the stragglers out there using Eclipse. But [Wayne Holder] thinks there’s a better way.

The project started out as a simple way for [Wayne] to program the ATtiny10 in C under Mac OS, but has since evolved into an open source, cross-platform integrated development environment (IDE) for programming a wide range of ATtiny chips in C, C++, or Assembly. Not only does it integrate the source code editor and programmer, but it even bundles in documentation for common variants of the chips including block diagrams and pinouts; making it a true one-stop-shop for ATtiny hacking.

His IDE runs under Java, including OpenJDK, and [Wayne] provides a stable pre-built executable for those who don’t want to clone the whole GitHub repository. He’s included the GNU/AVR toolchains, though notes that testing so far has been limited to Mac OS, and he’s interested in feedback from Windows and Linux users. Assembly is done either with GNU AVR-AS, or an assembler of his own design, though the latter is currently limited to the ATTiny10.

To actually get the code onto the chip, the IDE supports using the Arduino as a programmer as well as dedicated hardware like the BusPirate or the USBasp. If you go the Arduino route, [Wayne] has even come up with a little adapter board which he’s made available through OSH Park to help wrangle the diminutive chips.

The ATtiny10 might have something of a learning curve, but in exchange this family of tiny microcontrollers offers an incredible amount of capability. When you’re working with what’s essentially a programmable grain of rice, the only limit is your own creativity.