Give Your Solar Garden Lights A Color Changing LED Upgrade

White LEDs were the technological breakthrough that changed the world of lighting, now they are everywhere. There’s no better sign of their cost-effective ubiquity than the dollar store solar garden light: a complete unit integrating a white LED with its solar cell and battery storage. Not content with boring white lights on the ground, [Emily] decided to switch up their colors with a mix of single-color LEDs and dynamic color-changing LEDs, then hung them up high as colorful solar ornaments.

The heart of these solar devices is a YX8018 chip (or one of its competitors.) While the sun is shining, solar power is directed to charge up the battery. Once the solar cell stops producing power, presumably because the sun has gone down, the chip starts acting as a boost converter (“Joule thief”) pushing a single cell battery voltage up high enough to drive its white LED. Changing that LED over to a single color LED is pretty straightforward, but a color changing LED adds a bit of challenge. The boost converter deliver power in pulses that are too fast for human eyes to pick up but the time between power pulses is long enough to cause a color-changing circuit to reset itself and never get beyond its boot-up color.

The hack to keep a color-changing LED’s cycle going is to add a capacitor to retain some charge between pulses, and a diode to prevent that charge from draining back into the rest of the circuit. A ping-pong ball serves as light diffuser, and the whole thing is hung up using a 3D-printed sheath which adds its own splash of color.

Solar garden lights are great basis for a cheap and easy introduction to electronics hacking. We’ve seen them turn into LED throwies, into a usable flashlight, or even to power an ATTiny microcontroller.

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Hexagrow Robot Packs A Serious Sensor Package

Automation is a lofty goal in many industries, but not always straightforward to execute. Welding car bodies in the controlled environment of a production line is relatively straightforward. Maintaining plants in a greenhouse, however, brings certain complexities due to the unpredictable organic processes at play. Hexagrow is a robot that aims to study automation in this area, developed as the final year project of [Mithira Udugama] and team.

The robot’s chassis is a very modern build, consisting of carbon fiber panels and 3D printed components. This kind of strength is perhaps overkill for the application, but it makes for a very light and rigid robot when the materials are used correctly.

Testing soil pH isn’t easy, but Hexagrow is up to the challenge.

It’s the sensor package where this build really shines, however. There’s the usual accoutrement of temperature and humidity sensors, and a soil moisture probe, as we’d expect. But there’s more, including an impressive soil pH tester. This involves a robotic arm with a scoop to collect soil samples, which are then weighed by a load cell. This is then used to determine the correct amount of water to add to the sample. The mixture is then agitated, before being tested by the probe to determine the pH level. It recalls memories of the science packages on Mars rovers, and it’s great to see this level of sophistication in a university project build. There’s even a LIDAR mounted on top for navigation purposes, though it’s not clear as to whether this sensor is actually functionally used at this point in development.

Plants can be demanding of their caretakers, so perhaps you’d best check you’re measuring your soil moisture correctly? Video after the break.

[Thanks to Baldpower for the tip!]

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Gutters To Gardens: The IoT Rain Barrel

There’s nothing quite like having a garden in your backyard. You get tomatoes with flavor. Fresh herbs are easy. If you’d like to go crazy, you can always grow a gigantic pumpkin. But there’s a problem with gardening: the work. You’ve got to water, and you’ve got to weed. You’ve also got to deal with the thousand ladybugs you bought for a laugh.

For his Hackaday Prize entry, [Kent] has solved at least one of these problems. It’s an Internet of Things rain barrel. It’s designed to be as simple as possible so that anyone can set it up in just a few hours, and there’s also an option to make this rain barrel solar powered, making it eminently sustainable.

The design of this rain barrel begins as you would expect, with a 55-gallon rain barrel collecting water from [Kent]’s gutters. At the bottom of this barrel is a bunghole, and from that, a 12-volt pump sucks up the water and dispenses it into the garden bed. Everything is controlled through a Particle Photon, one of the easiest ways to set up an Internet of Things project, and yes, you can control this entire setup with an Alexa. The future is now.

Below, you can check out a few of the demo videos [Kent] put together for his project. One of them is solenoids clicking off to Deep Purple’s Smoke on the Water because if you’re going to build an Internet of Things thing with clicky electromechanical valves, you might as well make it play music.

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MoAgriS: A Modular Agriculture System

Hackaday.io user [Prof. Fartsparkle] aims to impress us again with MoAgriS, a stripped-down rig for bringing crops indoors and providing them with all they need.

This project is an evolution of their submission to last year’s Hackaday Prize, MoRaLiS — a modular lighting system on rails — integrating modules for light, water, airflow, fertilizer and their appropriate sensors. With an emphasis on low-cost, a trio of metal bars serve as the structure, power and data transmission medium with SAM D11 chips shepherding each plant.

Reinforced, angled PCBs extend rails horizontally allowing the modules to be mounted at separate heights. Light module? Up top. Water sensor? Low on the rails above the pot’s rim. You get the idea. 3D printed clamps attach the rails to the plant’s pot with a touch of paint to keep it from sticking out like a sore thumb among the leaves.

Airflow modules replicate wind currents — the lack of which results in thin, fragile stems — and light modules include a soft white LED to accompany and mitigate the full-spectrum LEDs’ pink neon-like glow. To manage watering the plants, [Prof. Fartsparkle] initially wanted to use one pump to distribute water to every plant, but found some smaller pumps at a low enough price-point to make one per plant viable — and simpler to integrate as a module as well!

If you prefer your gardening to take place outdoors, consider a robot assistant to tackle your weeding.

An Indoor Garden? That’s Arduino-licious

Gardening is a rewarding endeavour, and easily automated for the maker with a green thumb. With simplicity at its focus,  Hackaday.io user [MEGA DAS] has whipped up a automated planter to provide the things plants crave: water, air, and light.

[MEGA DAS] is using a TE215 moisture sensor to keep an eye on how thirsty the plant may be, a DHT11 temperature and humidity sensor to check the airflow around the plant, and a BH1750FVI light sensor for its obvious purpose. To deliver on these needs, a 12V DC water pump and a small reservoir will keep things right as rain, a pair of 12V DC fans mimic a gentle breeze, and a row of white LEDs supplement natural light when required.

The custom board is an Arduino Nano platform, with an ESP01 to enable WiFi capacity and a Bluetooth module to monitor the plant’s status while at home or away. Voltage regulators, MOSFETs, resistors, capacitors, fuses — can’t be too careful — screw header connectors, and a few other assorted parts round out the circuit. The planter is made of laser cut pieces with plenty of space to mount the various components and hide away the rest. You can check out [MEGA DAS]’ tutorial video after the break!

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Sensing Soil Moisture: You’re Doing It Wrong!

If you compulsively search online for inexpensive microcontroller add-ons, you will see soil moisture measurement kits. [aka] built a greenhouse with a host of hacked hardware including lights and automatic watering. What caught our attention among all these was Step 5 in their instructions where [aka] explains why the cheap soil sensing probes aren’t worth their weight in potting soil. Even worse, they may leave vacationers with a mistaken sense of security over their unattended plants.

The sensing stakes, which come with a small amplifier, work splendidly out of the box, but if you recall, passing current through electrodes via moisture is the recipe for electrolysis and that has a pretty profound effect on metal. [Aka] shows us the effects of electrolysis on these probes and mentions that damaged probes will cease to give useful information which could lead to overworked pumps and flooded helpless plants.

There is an easy solution. Graphite probes are inexpensive to make yourself. Simply harvest them from pencils or buy woodless pencils from the art store. Add some wires and hold them with shrink tube, and you have probes which won’t fail you or your plants.

Here’s some garden automation if this only whet your whistle, and here’s a robotic friend who takes care of the weeds for you.

Raspberry Pi Is The Brains Behind Automated Greenhouse

[Asa Wilson] and his wife picked up a 10’x12′ greenhouse from Harbor Freight that for their location required some serious changes, understandable since they’re in Colorado on the western slope of Pike’s Peak where the winds are strong and the normal growing season is short. After assembling it on a concrete footing and adding some steel bracing, they got to work on adding an environment management system based around a Raspberry Pi. Read on for a look at the modifications they made.

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