Push Big Red Button, Receive Power.

As with the age-old panic after realizing you have left an oven on, a candle lit, and so on, a soldering tool left on is a potentially serious hazard. Hackaday.io user [Nick Sayer] had gotten used to his Hakko soldering iron’s auto shut-off and missed that feature on his de-soldering gun of the same make. So, what was he to do but nip that problem in the bud?

Instead of modding the tool itself, he built an AC plug that will shut itself off after a half hour. Inside a metal project box — grounded, of course — an ATtiny85 is connected to a button, an opto-isolated TRIAC AC power switch, and a ‘pilot’ light indicating power. After a half hour, the ATtiny triggers the opto-isolator and turns off the outlet, so [Sayer] must push the button if he wants to keep working. He notes you can quickly double-tap the button for a simple timer reset.

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Debugging an Arduino with an Arduino

As every Hackaday reader knows, and tells us at every opportunity in the comments, adding an Arduino to your project instantly makes it twice as cool. But what if, in the course of adding an Arduino to your project, you run into a problem and need to debug the code? What if you could use a second Arduino to debug the first? That would bring your project up to two Arduinos, instantly making it four times as awesome as before you started! Who could say no to such exponential gains?

Debugging an ATTiny85

Not [Wayne Holder], that’s for sure. He writes in to let us know about a project he’s been working on for a while that allows you to debug the execution of code on an Arduino with a second Arduino. In fact, the target chip could even be another AVR series microcontroller such as a the ATTiny85. With his software you can single-step through the code, view and modify values in memory, set breakpoints, and even disassemble the code. Not everything is working fully yet, but what he has so far is very impressive.

The trick is exploiting a feature known as “debugWIRE” that’s included in many AVR microcontrollers. Unfortunately documentation on this feature is hard to come by, but with some work [Wayne] has managed to figure out how most of it works and create an Arduino Sketch that lets the user interact with the target chip using a simple menu system over the serial monitor, similar to the Bus Pirate.

[Wayne] goes into plenty of detail on his site and in the video included after the break, showing many of the functions he’s got working so far in his software against an ATTiny85. If you spend a lot of time working on AVR projects, this looks like something you might want to keep installed on an Arduino in your tool bag for the future.

Debugging microcontroller projects can be a huge time saver when your code starts running on real hardware, but often takes some hacking to get working.

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A Game That Does More With Less

[David Johnson-Davies] created a minimal Secret Maze Game using a single ATTiny85 and a few common components. This simple game uses four buttons, four LEDs, and a small speaker. The player moves in the four cardinal directions using buttons, and the LEDs show walls and corridors. If an LED is lit, it means the path in that direction is blocked by a wall, and attempting to move in that direction will make a beep. When the player reaches the exit, a short victory tune chirps from the speaker.

Sample maze. A 16×16 matrix is allocated for maze designs.

Since the ATTiny85 has only five I/O lines, [David] had to get a bit clever to read four buttons, display output on four LEDs, and drive a little speaker. The solution was to dedicate one pin to the speaker and the other four to charlieplexing, which is a method of driving more LEDs than you have pins. It takes advantage of the fact that most microcontroller pins can easily switch state between output high, output low, or low-impedance high-impedance input.

As for the buttons, [David] charlieplexed them as well. Instead of putting an LED in a charlieplexed “cell”, the cell contains a diode and an SPST switch in series with the diode. To read the state of the switch, one I/O line is first driven low and the other I/O line is made an input with a pullup. A closed switch reads low on the input, and an open switch reads high. With charlieplexing, four pins is sufficient for up to twelve LEDs (or buttons) in any combination, which is more than enough for the Secret Maze.

Charlieplexing is also what’s behind this 110 LED micro-marquee display, or this elegant 7-segment display concept that takes advantage of modern PCB manufacturing options.

Environmentally Aware Jewelry Gets Attention

We didn’t include a “Most Ornate” category in this year’s Coin Cell Challenge, but if we had, the environmentally reactive jewelry created by [Maxim Krentovskiy] would certainly be the one to beat. Combining traditional jewelry materials with an Arduino-compatible microcontroller, RGB LEDs, and environmental sensors; the pieces are able to glow and change color based on environmental factors. Sort of like a “mood ring” for the microcontroller generation.

[Maxim] originally looked for a turn-key solution for his reactive jewelry project, but found that everything out there wasn’t quite what he was looking for. It was all either too big or too complicated. His list of requirements was relatively short and existing MCU boards were simply designed for more than what he needed.

On his 30 x 30 mm PCB [Maxim] has included the bare essentials to get an environmentally aware wearable up and running. Alongside the ATtiny85 MCU is a handful of RGB LEDs (with expansion capability to add more), as well as analog light and temperature sensors. With data from the sensors, the ATtiny85 can come up with different colors and blink frequencies for the LEDs, ranging from a randomized light show to a useful interpretation of the local environment.

It’s not much of a stretch to imagine practical applications for this technology. Consider a bracelet that starts flashing red when the wearer’s body temperature gets too high. Making assistive technology visually appealing is always a challenge, and there’s undoubtedly a market for pieces of jewelry that can communicate a person’s physical condition even when they themselves may be unable to.

Form or function, life saving or complete novelty, there’s still time to enter your own project in the 2017 Coin Cell Challenge.

Geocache Locator Is The Gift That Keeps On Giving

Depending on how you look at things, the holidays could be seen as either an excuse to spend money or an excuse to get creative. We imagine many Hackaday readers would rather head to their workbench than the mall when it comes time for gift giving, and [Sean Hodgins] is no different. He came up with the idea of hiding geocaches around his nephew’s neighborhood and building him a locator device to find them. The locator itself is intended to grow with his nephew, allowing him to reprogram it or use its parts for something completely different down the road.

The main components tucked inside of the 3D printed case of the locator are an Adafruit Trinket, a GPS receiver, and a compass module. The Adafruit NeoPixel Ring is of course front and center, serving as the device’s display. To power the device there’s an old battery, a LiPo charger circuit, and a 5V converter.

One of the goals for the project was that it could be constructed out of things [Sean] already had laying around, so some concessions had to be made. The Trinket ended up having too few pins, the compass lacks an accelerometer, and the switches and buttons are a bit clunky for the build. But in the end it comes together well enough to get the job done, and at least he was able to clear some stuff out of his parts bins.

To allow its owner to disassemble and potentially rebuild it into something else later, no soldered joints were used in the construction of the locator. Everything is done with jumper wires, which lead to some interesting problem solving such as using a strip of pin header as a bus bar of sorts. A bit of heat shrink over the bundle holds everything together and prevents shorts.

Location-aware gadgets happen to be an extremely popular gift choice among the hacker crowd. We’ve covered everything from devices cobbled together from trash to hardware which could pass for a commercial product.

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Light Switch For The Lazy

[Will Donaldson] has whipped up a quick hack for anyone thinking of dipping their toe into home automation — or otherwise detest flicking off the bedroom light before navigating their way to their bed: a remote control light switch!

This remote switch uses a sg90 servo, an Arduino Uno, and pairs of ATtiny85s with HC-05 Bluetooth modules assembled on protoboards. The 3D printed mount screws easily on top of a standard light switch cover while still allowing the switch to be flipped the old-fashioned way. It’s also perfect as a temporary solution — [Donaldson] is presently renting his apartment — or for those unwilling to mess with the mains power of their abode.

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Upgrading A USB Soldering Iron!

Seeing the popularity of the TS-100 soldering iron, GitHub user [ole00] found himself desirous of a few of its features, but was put off by its lack of a power supply. What is a hacker to do? Find a cheaper option, and hack it into awesomeness.

[ole00] stumbled across the inexpensive ZD-20U and — despite a handful (sorry!) of issues — saw potential: it’s compact, lightweight, and powered via a USB power cable. Wanting to use as much of the ZD-20U’s original board as possible, the modifications were restricted to a few trace cuts and component swaps. The major change was swapping out the 555 timer IC controlling the iron with am ATtiny13a MCU to give it a bit more control.

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