Soil Moisture Sensors, How Do They Work?

In a way, the magic of a soil moisture sensor’s functionality boils down to a simple RC circuit. But of course, in practice there is a bit more to it than that. [rbaron] explains exactly how capacitive soil moisture sensors work simply, clearly, and concisely. He also shows, with a short video, exactly how their output changes in response to their environment, and explains how it informed his own sensor design.

At its heart, a moisture sensor measures how quickly (or slowly) a capacitor charges through a resistor, but in these sensors the capacitor is not a literal component, but is formed by two PCB traces that are near one another. Their capacitance — and therefore their charging rate — changes in response to how much water is around them. By measuring this effect on a probe sunk into dirt, the sensor can therefore indirectly measure the amount of water in the soil.

This ties into his own work on b-parasite: an open-source, all-in-one wireless soil moisture sensor (which was also a runner-up in our Earth Day contest) that broadcasts over BLE and even includes temperature readings. One thing to be mindful of if you are making your own PCBs or ordering them from a fab house is that passing current through metal in a moist environment is a recipe for oxidation, so it’s important not to expose bare traces to wet soil. A good coated PCB should avoid this problem, but one alternative we have seen proposed is to use graphite rods in place of metal.

Sit Pretty On Would-Be Garbage With An Upcycled Chair

What’s the coolest thing about doing upholstery work? Aside from the fact that you end up with a new thing to sit on, sometimes the work only involves clever stapling, and no sewing is necessary. Such is the case with [wyldestyle]’s upcycled jeans chair, which started as a bare-wood swivel number from the dump. In fact, this project is almost completely made from recycled materials, except of course for those staples that hold it all together. And really, that heavy-duty stapler is likely the fanciest tool you’d need to make your own.

[wyldestyle] didn’t have any furniture foam, and we think that stuff is too expensive, anyway. So the padding treatment begins with a piece of thick Styrofoam that covers the seat screws and bolts. This is glued in place and trimmed down to match the contours of the chair’s seat and back.

Here’s where things gets tricky: the next step is wrapping over the stiff foam board with a few layers of that foam sheeting stuff that’s often used as packing material. This sheeting needs to be taut, but pull it too tight, and it will rip.

To add some loft to the chair, [wyldestyle] stretched and stapled the stuffing from an old pillow that was headed for the garbage. The final step is strategically scissoring jean scraps to fit, then stretching and stapling those to cover all the layers underneath. We like the way this chair looks, and would probably try to place pockets somewhere useful, like the back of the chair.

It’s a shame that so much denim goes to waste all over the world. There’s often a lot of life left in most of the fabric, which can be repurposed into all kinds of things, including eyeglasses frames using a wicked set of jigs.

South Australia Vs. Too Much Home Solar

Once upon a time, the consensus was that renewable energy was too expensive and in too sparse supply to be a viable power source to run our proud, electrified societies on. Since then, prices of solar panels have tanked, becoming more efficient along the way, and homeowners have been installing them on their rooftops in droves.

Where once it was thought we’d never have enough solar energy, in some cities, it’s becoming all too much. In South Australia, where solar output can be huge on a sunny day, electricity authorities are facing problems with grid stability, and are taking measures to limit solar output to the grid.

Isn’t More Usually Better?

The problem faced by South Australian utilities is one of how to properly control an electrical grid with many thousands of distributed power sources. Typically, in conventional modern power grids, voltage and frequency is controlled within set limits by carefully matching the supply from major power plants with the demand from users. Fast-response plants can be brought online to meet shortfalls, and switched off when demand drops, and everything hums along nicely.

Unfortunately, solar power isn’t so easy to throttle, and even less so when it’s coming from thousands of separate households each with their own rooftop install and an inverter to feed back into the grid. This has led to authorities contemplating measures such as charging homeowners to export energy to the grid in peak periods in an effort to slow the huge uptake of home solar systems. Export limits have also been proposed for suburbs with the highest concentration of home solar, as substations in certain residential areas struggle to cope under the huge inflows of energy. Continue reading “South Australia Vs. Too Much Home Solar”

Automate Your Poultry With CoopCommand

A fresh egg taken from beneath a slumbering hen is something to which the taste of a supermarket equivalent rarely compares. The satisfaction of having a contented flock does come at a price though, in the form of constant monitoring and husbandry of your poultry’s well-being. It’s a problem that [hms-11] has tried to address with CoopCommand, a system to automate the monitoring of and environment within a chicken coop. It controls a light to counteract for shorter winter days, warms their water when it’s cold, has a fan for cooling and ventilation on hot days, and a camera to keep any eye on them.

At its heart is an ATmega328 controlling the coop functions, and an ESP32 camera board for network connectivity and visual monitoring. An alphanumeric LCD and a set or buttons provide the interface, and all is fitted on a custom PCB in a smart 3D-printed housing. Meanwhile all the files can be found in a GitHub repository.

A machine cannot replace human care and attention when it comes to good animal husbandry, as there’s always an essential need for the poultry owner to attend to the needs of their charges. But a system like this one can make an important contribution to their welfare, with a consequent increase in their laying ability.

Solar And Wind Could Help Support Ethiopia’s Grand Dam Project

Ethiopia is in the midst of a major nation-building project, constructing the Grand Ethiopian Renaissance Dam (GERD). Upon completion, GERD will become the largest hydropower plant in Africa, providing much needed electricity for the country’s growing population.

The project dams the Blue Nile, a river which later flows into neighbouring Sudan, where it merges with the White Nile and then flows on to Egypt. Like all rivers that flow across political boundaries, concerns have been raised about the equitable management of the water resources to the benefit of those upstream and down. Too much water dammed upstream in GERD could have negative effects on Egyptian agriculture reliant on river flows, for example. Efforts are ongoing to find a peaceful solution that suits all parties. Recently, suggestions have been made to supplement the dam’s power output with solar and wind to minimise disruption to the river’s users.

Continue reading “Solar And Wind Could Help Support Ethiopia’s Grand Dam Project”

Blocking Out The Sun: Viable Climate Countermeasure Or Absolute Madness?

If there’s one thing humans hate, it’s exercising willpower. Whether its abstaining from unhealthy foods, going to bed early, or using less energy and reducing greenhouse gas emissions, we’re famously bad at it. Conversely, if there’s one thing humans love, it’s a workaround. Something that lets us live our lives as the carefree hedonists we are, and deals with the sticky consequences so we don’t have to.

One such workaround for the issue of climate change is a doozy, though — blocking out the sun’s rays in order to cool our warming planet.

Continue reading “Blocking Out The Sun: Viable Climate Countermeasure Or Absolute Madness?”

“Paper” Bottles For Your Fizzy Drinks (And Bottle Rockets)

A story that passed almost unnoticed was that the Coca-Cola company plan to run a limited trial of paper bottles. Wait, paper for a pressurized beverage? The current incarnation still uses a plastic liner and cap but future development will focus on a “bio-based barrier” and a bio composite or paper cap tethered to the vessel.

Given that plastic pollution is now a major global concern this is interesting news, as plastic drinks bottles make a significant contribution to that problem. But it raises several questions, first of all why are we seemingly unable to recycle the bottles in the first place, and given that we have received our milk and juice in paper-based containers for decades why has it taken the soda industry so long?

Plastic soft drink bottles are made from Polyethylene terephthalate or PET, the same polyester polymer as the one used in Dacron or Terylene fabrics. They’re blow-moulded, which is to say that an injection-moulded preform something like a plastic test tube with a screw top fitting is expanded from inside in a mould by compressed gas. As anyone who has experimented with bottle rockets will tell you, they are immensely strong, and as well as being cheap to make and transport they are also readily recyclable when separated from their caps.

Continue reading ““Paper” Bottles For Your Fizzy Drinks (And Bottle Rockets)”