Our Coin Cell Challenge competition has turned up some amazing entries, things that we wouldn’t have thought possible from such meagre power sources. Take [Vishnu M Aiea]’s entry for instance, a device which he claims can light up as a birthday reminder every year for up to fifty years.

At its heart is a modified Arduino Nano clone that draws a measured 608 nA from a CR2450N. From the specification of the cell he has calculated the 50 year maximum figure, as well as a possible 29 years for a CR2032 and 64 years for a CR2477. He does however note that this does not take self-discharge into account, but you can probably afford a new battery in a decade or so.

The Arduino clone carefully selected for its “P” version low-power processor has had its serial bridge IC removed to achieve this power consumption, as well as a voltage regulator and some discrete components. Interestingly he notes that the ATMega168P is even more frugal than its 328 cousin, so he’s used the former chip. A selection of internal flags are set for minimal power consumption, and the internal oscillator is selected to use as low a clock speed as possible. There is an Intersil ISL1208 low power RTC chip mounted on a piece of stripboard to provide the timing, and of course an LED to provide the essential birthday alert.

When the LED lights for the big day there’s always the hope you’ll receive another coin cell, this time powering an edge-lit musical birthday card.

Making someone a birthday cake is very thoughtful, but not if they are watching their weight. [MrFox] found a way around that: an Arduino-powered birthday cake. Even if you don’t mind the calories, an Arduino cake is a novelty and sure to be a hit with a hacker who’s another year older.

The cake uses a UTFT LCD shield which eats up a lot of pins and memory, so the project uses an Arduino Mega. A speaker plays the happy birthday song (which may even be legal now) while a microphone detects the birthday boy or girl blowing out the virtual candles.

We’ve seen similar cakes with a fixed number of LED “candles” before, but the LCD screen makes this a cake of a different color. If you want, you could look into something that is actually edible. On the other hand, we’re kind of partial to the Jolly Wrencher with red eyes and fireworks, ourselves.

The video shows the birthday cake in action. Given the screen, we were surprised that nothing popped out. Not a life-changing project, but still fun for your next hacker party, even if you have a real cake as a backup.

At the end of March Arduino Day was celebrated around the world in more than 260 official and community events. In the video below Massimo Banzi, David Cuartielles, Tom Igoe and David Mellis sent a message to the whole community from the celebration taking place at MIT in Boston:

Take a look at some pictures from official Arduino Day which happened in Boston, Torino, Malmo, Budapest and Bangalore and some birthday cakes popping up on Twitter:

Hoy es Arduino Day #ArduinoD15: ¡¡¡Feliz cumpleaños Arduino!!! Para los que no conocen Arduino; es una platafo… http://t.co/DKCp58gNQp

— StreaMexico (@Stream_Mexico) April 1, 2015

I found #awesomesauce! ???? ?? #ArduinoD15 #arduino #arduinoday #hack #logo #community… … http://t.co/YmZbEF82Ej pic.twitter.com/jE2vglF65e

— Clarke Hosp (@hospdesign) April 2, 2015

#ArduinoD15 and then they brought cake! Awesome thanks @Creating_STEAM pic.twitter.com/GTC6QJGasN — Caren Watkins (@ThisIsCaren) March 28, 2015

It’s Arduino Day! One of our founders @timredfern made a cake version of an @arduino board to celebrate. #ArduinoD15 pic.twitter.com/yN7GVzcPiX

— Drop (@dropkitchen) March 28, 2015

We also wanted to share  links some  organizers sent us to explore pictures/videos of local communities’ gatherings:

• Arduino Day Talent Lab Padova (Italia)
• Arduino Day Wemake Milano (Italia)
• Arduino Day Het Lab Rotterdam (Nederlands)
• Arduino Day Dubrovnik (Croatia)
• Arduino Day Gliwice (Poland) – Pictures and Video
• Arduino Day Bonevet – Djakovica (Kosovo)
• Club Arduino Argentina
• Arduino Day Bangladesh
• Arduino Day Caruaru (Brasil)
• Unoesc Chapeco (Brasil)
• Arduino Day Campinas (Brasil) - blogpost
• IFSP Votuporanga (Brasil) – Video
• Arduino Day Passo Fundo, RS (Brasil)
• Arduino Day ICMC USP (Brasil)
• Arduino Day Bauru (Brasil)
• Arduino Day Epsem
• Arduino Day 2015 Batangas
• Arduino Day Puerto Rico
• Arduino Day Harris County Public Library (Houston, Texas)
• Arduino Day Puerto Madryn, Chubut (Argentina)
• Arduino Day Melbourne Makerspace (Australia)
• Arduino Day Costa Rica
• Arduino Day Sat Montreal (Canada)
• Arduino Day Wikilogia Damasco (Sirya)
• Arduino Day Buffalo Lab New York (USA)
• Arduino Day Casablanca (Morocco)
• Arduino Day Medellin (Colombia)
• Arduino Day Cartagena (Colombia)
• Arduino Day Harringay
• Arduino Day Nerdlab, Gent (Belgium)

Do you have pictures and videos to share of your Arduino Day? Post the link in the comments!

[Apachexmd] wanted to do something fun for his three-year-old son’s birthday party. Knowing how cool race cars are, he opted to build his own Hot Wheels drag race timer. He didn’t take the easy way out either. He put both his electronics and 3D printing skills to the test with this project.

The system has two main components. First, there’s the starting gate. The cars all have to leave the gate at the same time for a fair race, so [Apachexmd] needed a way to make this electronically controlled. His solution was to use a servo connected to a hinge. The hinge has four machine screws, one for each car. When the servo is rotated in one direction, the hinge pushes the screws out through holes in the track. This keeps the cars from moving on the downward slope. When the start button is pressed, the screws are pulled back and the cars are free to let gravity take over.

The second component is the finish line. Underneath the track are four laser diodes. These shine upwards through holes drilled into the track. Four phototransistors are mounted up above. These act as sensors to detect when the laser beam is broken by a car. It works similarly to a laser trip wire alarm system. The sensors are aimed downwards and covered in black tape to block out extra light noise.

Also above the track are eight 7-segment displays; two for each car. The system is able to keep track of the order in which the cars cross the finish line. When the race ends, it displays which place each car came in above the corresponding track. The system also keeps track of the winning car’s time in seconds and displays this on the display as well.

The system runs on an Arduino and is built almost exclusively out of custom designed 3D printed components. Since all of the components are designed to fit perfectly, the end result is a very slick race timer. Maybe next [Apachexmd] can add in a radar gun to clock top speed. Check out the video below to see it in action.