Hacklet 26 – Arduino Projects

Arduino is one of those boards that has become synonymous with hacking and making. Since its introduction in 2005, over 700,000 official Arduino boards have been sold, along with untold millions of compatible and clone boards. Hackers and makers around the world have found the Arduino platform a cheap and simple way to get their projects off the ground. This weeks Hacket focuses on some of the best Arduino based projects we’ve found on Hackday.io!

drawingbot[Niazangels] gets the ball – or ballpoint pen – rolling with Roboartist, a robot which creates line drawings. Roboartist is more than just a plotter though. [Niazangels] created a custom PC program which creates line drawings from images captured by a webcam. The line drawings are converted to coordinates, and sent to an Arduino, which controls all the motors that move the pen. [Niazangels] went with Dynamixel closed loop servo motors rather than the stepper motors we often see in 3D printers.

tape[Peter Edwards] is preserving the past with Tapuino, the $20 C64 Tape Emulator. Plenty of programs for the Commodore 64, 128, and compatibles were only distributed on tape. Those tapes are slowly degrading, though the classic Commodore herdware is still going strong. Tapuino preserves those tapes by using an Arduino nano to play the files from an SD card into the original Datasette interface. [Peter] also plans to add recording functionality to the Tapuino, which will make it the total package for preserving  your data. All that’s missing is that satisfying clunk when pressing the mechanical Play button!

infinity

[Dushyant Ahuja] knows what time it is, thanks to his Infinity Mirror Clock. This clock tells time with the help of some WS2812B RGB LED. [Dushyant] debugged the clock with a regular Arduino, but when it came time to finish the project, he used an ATmega328 to create an Arduino compatible board from scratch. Programming is easy with an on-board Bluetooth module. [Dushyant] plans to add a TFT lcd which will show weather and other information when those power-hungry LEDs are switched off.

alarm2[IngGaro] built an entire home alarm system with his project Arduino anti-theft alarm shield. [IngGaro] needed an alarm system for his home. That’s a lot to ask of a standard ATmega328p powered Arduino Uno. However, the extra I/O lines available on an Arduino Mega2560 were just what the doctor ordered. [IngGaro] performed some amazing point-to-point perfboard wiring to produce a custom shield that looks and works great! The alarm can interface with just about any sensor, and can be controlled via the internet. You can even disarm the system through an RFID keycard.

Want MORE Arduino in your life? Check out our curated Arduino List!

That’s about all the millis()  we have for this weeks Hacklet. As always, see you next week. Same hack time, same hack channel, bringing you the best of Hackaday.io!

Joule Thief Steals Power for a Clock

A common project among electronics tinkerers is the joule thief, a self-oscillating circuit that can “steal” the remaining energy in a battery after the voltage has dropped so low that most devices would stop working. Typically the circuit powers an LED until almost all of the energy is extracted from the battery, but [Lionel Sears] has created a specialized joule theif that uses the “extra” energy to power a clock.

The circuit uses four coils instead of the usual two to extract energy from the battery. The circuit charges a large capacitor which provides the higher current pulses needed to drive the clock’s mechanism. It can power the clock from a single AA battery, and will run until the voltage on the battery is only 0.5 volts.

Normally the clock would stop running well before the voltage drops this low, despite the fact that there’s still a little chemical energy left in the batteries. The circuit can drive the clock for an extended time with a new battery, or could use old “dead” batteries to run the clock for a brief time while the final little bit of energy is drawn from them. If you’re so inclined, you could even use hot and cold water with a joule thief to run your clock! Thanks to [Steven] for the tip.

Hack a Solar Garden Light Into a Flashlight

solargardenflashlight

While browsing through his local dollar store, [Taylor] came across a suspicious looking rock that, upon closer inspection, turned out to be a solar garden light. He scooped it up, took it home and cracked it open, modding it to function as a handheld solar flashlight.

Inside was a pathetically small 40mAh rechargeable battery, which he upgraded to a more standard rechargeable AA. The garden rock came pre-built with its own boost converter to kick up the voltage for the LED, but it was fairly dim. We’re guessing [Taylor] didn’t bother reverse engineering the converter and instead simply did some trial and error, but he managed to increase the LED’s brightness by slapping on a different value inductor.

As fun as it may be to have a rock for a flashlight, [Taylor] decided to cobble together a custom case out of a spare USB charger, making a battery holder and adding a pushbutton. The result is a handy solar flashlight that takes around five hours to charge. Check out some other custom lights: a lithium-powered PVC flashlight or one with a snazzier aluminum body and interchangeable heads.

Measuring the capacities of different battery brands

Being the smart consumer he is, [Denis] usually looks at the price per pound when comparing similar products at the grocery store. When it came time to buy a few AA batteries, he didn’t have any data to go on. To solve his little conundrum, [Denis] decided he would test several brands of batteries and see which one gives him the most bang for the buck.

After bringing home a haul of a dozen different brands of AA cells, [Denis] broke out the Arduino and starting designing a circuit. To test how much energy each brand provides, the Arduino measures the voltage across a load every second until the battery reaches 0.2V. The elapsed time, as well as the voltage, Watt hours, Joules, and ambient temperature are logged on an attached LCD screen and sent over a USB serial link to automate the data collection process.

What’s the verdict? Unsurprisingly, words like ‘super,’ ‘max,’ and ‘ultra’ didn’t connotate a better battery. The best bang for the buck came from an off-brand called RS Power Ultra. The worst battery was the Panasonic Evolta cells that came in at about $1.50 USD per watt-hour.

If you’d like to verify [Denis]’ work, all the code is up on Github along with the schematic.