Trivia Lock Box Spices up Wedding Reception

Any hardware hacker will tell you, a significant other who embraces your passion is a keeper. [Nathan] found a keeper in [Jessica] – they even worked together on a hardware hack for their own wedding. The couple wanted an interactive element for their guests. Disposable cameras are getting a bit hard to find these days, so the solution was a trivia powered lock box designed and built by [Nathan] himself. Guests arrived at their tables to find locked boxes and cards with trivia questions about the couple. Only by answering the questions correctly would they unlock the box to access the prizes inside.

Each box consists of a Really Bare Bones Board, which is essentially an ATmega328 breakout board. The user interface consists of five tactile switches and a 16×2 character based LCD. The box is a clear Vaultz pencil box (Yes, the same brand Ahmed used for his clock). The final element is of course the locking mechanism. One of [Nathan’s] friends noticed that the Vaultz box latch was riveted in, and was spring loaded. It only took a bit of work to flip the latch from the outside to the inside. Cheap 9g micro servos from the far east pull the latch open with a string. The only thing we haven’t figured out is how [Nathan] closed the latches while they were inside the box. Obviously some black magic was involved! [Jessica] decorated the box with circuit traces created on her vinyl cutter.

On the eve of the big day, [Nathan] realized that his tactile switches were… not really switching. The superglue he had used to mount them had seeped into the switch body, freezing it solid. Nathan saved the project with a herculean effort of soldering 5 switches on each of 12 boxes the night before his own wedding.

What was in the box? Alka-Seltzer tablets. When added to vases filled with oil and water, the fizzy tablets turned the vases into mini lava lamps. The boxes also contained coins which were redeemable for Hawaiian Leis.

Click past the break to see the boxes in action on [Nathan] and [Jessica’s] big day and if you’re looking to build a fleet of hardware for your own wedding, take a look at the centerpieces [Bill Porter] created a couple of years ago.

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Code Craft – Embedding C++: Classes

For many embedded C developers the most predominate and questionable feature of C++ is the class. The concern is that classes are complex and therefore will introduce code bloat and increase runtimes in systems where timing is critical. Those concerns implicate C++ as not suitable for embedded systems. I’ll bravely assert up front that these concerns are unfounded.

When [Bjarne Stroustrup] created C++ he built it upon C to continue that language’s heritage of performance. Additionally, he added features in a way that if you don’t use them, you don’t pay for them.

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The Robot Light Switch

Automating your home is an awesome endeavor — but playing with mains AC can be risky business if you don’t know what you’re doing. So why not play it safe and make use of your light switch?

Admittedly, it wasn’t because [Tyler Bletsch] didn’t want to mess around with AC directly, but rather out of necessity. You see, he just moved into a new office and his “smart” air conditioner… doesn’t turn itself off at night.

There’s a remote control to set the target temperature, but the unit isn’t smart enough to turn off at night. Instead, there’s a physical wall switch so you can turn it off with your actual physical hands, like a barbarian.

Refusing to be a barbarian (and to stay at work late), he decided to simplify the problem by building a servo driven light switch plate. It’s not the prettiest — but it does the trick. Continue reading “The Robot Light Switch”

Automatic Cat Feeder Dispenses Noms, Wants Cheezburger

[Domiflichi] likes his cats, but not the drudgery of feeding them. So, like any good engineer, this simple problem became his next project: building an automatic cat feeder. Based on an Arduino, his creation beeps to let the cats know that it is dinnertime, then dispenses food into a number of bowls. There are also buttons for manual control. This lets him give individual cats a separate feeding. Rounding out the feature set, a DS1307 RTC tracks the feeding times.

One of the most interesting parts of his build is the transfer from breadboard to protoboard. This usually involves taking apart a working version, then putting it back together and trying to figure out why it doesn’t work anymore. [Domiflichi]’s problem (detailed in a follow-up post) was figuring out how to program the real-time clock module to set the time, because it looses the time when you disconnect the power. Rather than use the Arduino to program the RTC,  he used the battery backup feature of the RTC chip, programming it on his computer and then soldering it onto the board. He went on to remove the backup battery after the chip was in place. That’s a solution that will no doubt have many readers waving their fingers disapprovingly, but it worked.

It may seem overly complicated, but his project is worth checking out to see how he approached some of the engineering challenges. The food hoppers themselves are off-the-shelf cereal dispensers. We’ve seen other designs bootstrap this mechanism with 3D printed augers.

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Magnetic Levitation with Arduino

Getting a magnetic field to balance on another magnetic field is about as easy as balancing a bowling ball on the tip of an ink pen. With a little help from an Arduino mega, however, [EmmaSong] was able to balance a high density neodymium magnet in midair. He pulled off this tricky project using a set of four coils he got off of Taobao (the Chinese version of eBay), a hall effect sensor, and a handful of current regulation ICs.

The coils can be made in house if necessary, with each winding getting about 800 turns of enameled wire. The rest of the circuit is straightforward. It appears he uses a potentiometer for a rough regulation of the current going to the coils, doing the fine tuning in the code which can be found here (.RAR direct download).

We’ve seen magnetic levitation here before, and this project adds to the list of successful techniques to accomplish this difficult project.

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PIR Jack-o-Lantern Sees Them Coming

Planning to make that carved a pumpkin last past Halloween night? Forget the tealight or LED candle—here’s an easy, no-solder project that will make it extra special. By default, this jack-o-lantern looks like it has a flickering flame, but get close enough to it and it goes crazy with color.

All you need is an LED matrix, a Rainbowduino to drive it, a PIR motion sensor to trigger the random colors, and a power source. [Alpha Charlie] kept the electronics from becoming pumpkin-flavored with some plastic bags. Since he used the PIR as the jack-o-lantern’s nose, there is a bit of plastic behind it to keep moisture from interfering.

[Alpha Charlie]’s build instructions are quite detailed, which makes this project even simpler if you’ve never used a PIR before. There are lots of ways you could build on this project to make it your own, like using trick-or-treater motion to trigger screams or spooky sounds, or add more sensors to make it more interactive. Watch it react after the break.

If you have nothing else at all to do between now and trick-or-treat time, you could bust out the soldering iron and recreate this 70-LED matrix jack-o-lantern. Blinkenlights too safe for your tastes? Fire-breather it is, then.

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Code Craft: Using Eclipse for Arduino Development

As we work on projects we’re frequently upgrading our tools. That basic soldering iron gives way to one with temperature control. The introductory 3D printer yields to one faster and more capable. One reason for this is we don’t really understand the restrictions of the introductory level tools. Sometimes we realize this directly when the tool fails in a task. Other times we see another hacker using a better tool and realize we must have one!.

The same occurs with software tools. The Arduino IDE is a nice tool for starting out. It is easy to use which is great if you have never previously written software. The libraries and the way it ties nicely into the hardware ecosystem is a boon.

When you start on larger projects, say you upgrade to a Due or Teensy for more code or memory space, the Arduino IDE can hamper your productivity. Moving beyond these limitations requires a new, better tool.

Where do we find a better tool? To begin, recognize, as [Elliot] points out that There is no Arduino “Language”, we’re actually programming in C or C++. We chose which language through the extension on the file, ‘c’ for C and ‘cpp’ for C++. An Arduino support library may be written in C or C++ depending on the developer’s preference. It’s all mix ‘n match.

Potentially any environment that supports C/C++ can replace the Arduino IDE. Unfortunately, this is not easy to do, at least for inexperienced developers, because it means setting up the language tool chain and tools for uploading to the board. A developer with that much experience might eschew an integrated development environment altogether, going directly to using makefiles as [Joshua] describes in Arduino Development; There’s a Makefile for That.

The reality is the Arduino IDE is not much more than a text editor with the ability to invoke the tools needed to compile and download the code to the Arduino. A professional IDE not only handles those details but provides additional capabilities that make the software development process easier.

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