Planet Arduino

Logging data with an Arduino is old-hat for most Hackaday readers. However, [Patricia Beddows] and [Edward Mallon] had some pretty daunting requirements. Their sensors were going underground and underwater as part of an effort to study conditions underwater and in caves. They needed to be accessible, yet rugged. They didn’t want to use batteries that would be difficult to take on airplanes, but also wanted more than a year of run time. You can buy all that, of course, if you are willing to pay the price.

Instead, they used off-the-shelf Arduino boards connected together inside PVC housings. Three alkaline AA batteries are compact and give them more than a year of run time. They wrote a journal paper to help other scientists use the same techniques for the Sensors journal published by the Multidisciplinary Digital Publishing Institute.

If you regularly read Hackaday, you probably won’t find the electronic part of the build remarkable. However, that’s kind of the point, as this is all off-the-shelf and inexpensive. They do however modify the boards in some cases to allow the controller to power them down, for example.

In fact, they put a lot of thought into reducing power requirements. Since your eye is more sensitive to green, for example, they use green LEDs with very low currents as indicators. They also speed up the serial bus going to sensors because they found that the increased power required was more than offset by finishing the transaction faster (and, thus, going back to sleep sooner).

The PVC enclosures are also interesting. The paper shows some practical deployments in some very harsh conditions. If you want more practical details, the Cave Pearl project has been blogging about their development of these loggers for a while. They have a good “how to” page, as well.

If an Arduino seems too last-year for you, we’ve seen long-duration logging done with ESP8266s and ESP32s. However, they did use lithium-ion cells. Spoiler alert: The ESP8266 lasts longer than the ESP32. If you want to minimize power when sending things out over a network connection, consider MQTT.

As part of an electrical and electronic engineering course at Singapore Polytechnic, a group of students were challenged to build an aquatic vehicle that could collect samples from one and two meters underwater. After three months of hard work, the Imp Bot was brought to life!

Imp Bot is controlled by a mobile application made using the MIT App Inventor. Communication is achieved via a Bluetooth module hooked up to an Arduino Mega, while an onboard GPS sensor is used to log sampling locations in the app. Power is provided by a LiPo battery, which supplies high current to the two DC motors responsible for moving the 11-pound vessel around.

The sampler is actually a simplified Van Dorn Water Sampler, an ingenious method of water collection based upon elasticity and a quick-release mechanism. The main body of the vessel was initially made using laser-cut acrylic pieces assembled with PVC pipes, but the structure was too weak so they decided to use aluminium L-brackets instead.

Want to learn more? Check out the team’s video below, as well as read the story on one of the student’s blogs here. The code is also available on GitHub.

Bonsai trees are not like other plants. There’s no single watering schedule that can be applied to a bonsai and the best way to tell if the bonsai needs water is to touch the soil. Experienced growers know when a tree needs to be watered by observing the foliage or just by the weight of the pot. If you are not used to taking care of this type of tree, Bonsai Watchdog could be the perfect project for you. It runs on Arduino and Genuino Uno and makes it really easy to monitor the moisture level in the soil.

Thomas Baum, created it and shared it some days ago on the Arduino Community on G+ :

Two pencil leads, an Arduino and a 12864 (ST7565) LCD watches out my little bonsai. The filling level shows how often the sapling need to be watered.
source and discription (in german) you can find here:
http://tiny.systems/categorie/lcdProjekt/BonsaiWatchdog.html

The robotic prototype swimming under water propelled by fins, it was developed at the Control Systems and Robotics Laboratory of the Technological Educational Institute of Crete, in Heraklion (Greece) and it’s controlled by an Arduino Mega:

Each fin is comprised of three individually actuated fin rays, which are interconnected by an elastic membrane. An on-board microcontroller generates the rays’ motion pattern that result in the fins’ undulations, through which propulsion is obtained. The prototype, which is fully untethered and energetically autonomous, also integrates an IMU/AHRS unit for navigation purposes, a wireless communication module, and an on-board video camera. The video contains footage from experiments conducted in a laboratory test tank to investigate closed loop motion control strategies, as well as footage from sea trials.

the Arduino runs a custom-developed real time firmware that implements two Central Pattern Generator (CPG) networks to generate the undulatory motion profile for the robot’s fins. The robot  contains a  7.4V lipo battery powering also a Bluetooth module for wireless communication and a video camera to record footage of the missions.